bluuebunny/crossref_metadata_2025 huggingface dataset:
Golgi Structure Correlates with Transitional Endoplasmic Reticulum Organization in Pichia pastoris and Saccharomyces cerevisiae
Authors: Rossanese Olivia W. , Soderholm Jon , Bevis Brooke J. , Sears Irina B. , O'Connor James , Williamson Edward K. , Glick Benjamin S.
Published: July 2002

Golgi stacks are often located near sites of “transitional ER” (tER), where COPII transport vesicles are produced. This juxtaposition may indicate that Golgi cisternae form at tER sites. To explore this idea, we examined two budding yeasts: Pichia pastoris, which has coherent Golgi stacks, and Saccharomyces cerevisiae, which has a dispersed Golgi. tER structures in the two yeasts were visualized using fusions between green fluorescent protein and COPII coat proteins. We also determined the localization of Sec12p, an ER membrane protein that initiates the COPII vesicle assembly pathway. In P. pastoris, Golgi stacks are adjacent to discrete tER sites that contain COPII coat proteins as well as Sec12p. This arrangement of the tER-Golgi system is independent of microtubules. In S. cerevisiae, COPII vesicles appear to be present throughout the cytoplasm and Sec12p is distributed throughout the ER, indicating that COPII vesicles bud from the entire ER network. We propose that P. pastoris has discrete tER sites and therefore generates coherent Golgi stacks, whereas S. cerevisiae has a delocalized tER and therefore generates a dispersed Golgi. These findings open the way for a molecular genetic analysis of tER sites.
Dynactin Is Required for Microtubule Anchoring at Centrosomes
Authors: Quintyne N.J. , Gill S.R. , Eckley D.M. , Crego C.L. , Compton D.A. , Schroer T.A.
Published: July 2002

The multiprotein complex, dynactin, is an integral part of the cytoplasmic dynein motor and is required for dynein-based motility in vitro and in vivo. In living cells, perturbation of the dynein–dynactin interaction profoundly blocks mitotic spindle assembly, and inhibition or depletion of dynein or dynactin from meiotic or mitotic cell extracts prevents microtubules from focusing into spindles. In interphase cells, perturbation of the dynein–dynactin complex is correlated with an inhibition of ER-to-Golgi movement and reorganization of the Golgi apparatus and the endosome–lysosome system, but the effects on microtubule organization have not previously been defined. To explore this question, we overexpressed a variety of dynactin subunits in cultured fibroblasts. Subunits implicated in dynein binding have effects on both microtubule organization and centrosome integrity. Microtubules are reorganized into unfocused arrays. The pericentriolar components, γ tubulin and dynactin, are lost from centrosomes, but pericentrin localization persists. Microtubule nucleation from centrosomes proceeds relatively normally, but microtubules become disorganized soon thereafter. Overexpression of some, but not all, dynactin subunits also affects endomembrane localization. These data indicate that dynein and dynactin play important roles in microtubule organization at centrosomes in fibroblastic cells and provide new insights into dynactin–cargo interactions.
Late Onset Death of Motor Neurons in Mice Overexpressing Wild-Type Peripherin
Authors: Beaulieu Jean-Martin , Nguyen Minh Dang , Julien Jean-Pierre
Published: July 2002

Peripherin, a type III intermediate filament (IF) protein, upregulated by injury and inflammatory cytokines, is a component of IF inclusion bodies associated with degenerating motor neurons in sporadic amyotrophic lateral sclerosis (ALS). We report here that sustained overexpression of wild-type peripherin in mice provokes massive and selective degeneration of motor axons during aging. Remarkably, the onset of peripherin-mediated disease was precipitated by a deficiency of neurofilament light (NF-L) protein, a phenomenon associated with sporadic ALS. In NF-L null mice, the overexpression of peripherin led to early- onset formation of IF inclusions and to the selective death of spinal motor neurons at 6 mo of age. We also report the formation of similar peripherin inclusions in presymptomatic transgenic mice expressing a mutant form of superoxide dismutase linked to ALS. Taken together, these results suggest that IF inclusions containing peripherin may play a contributory role in motor neuron disease.
N-Cadherin Promotes Motility in Human Breast Cancer Cells Regardless of Their E-Cadherin Expression
Authors: Nieman Marvin T. , Prudoff Ryan S. , Johnson Keith R. , Wheelock Margaret J.
Published: July 2002

E-cadherin is a transmembrane glycoprotein that mediates calcium-dependent, homotypic cell–cell adhesion and plays a role in maintaining the normal phenotype of epithelial cells. Decreased expression of E-cadherin has been correlated with increased invasiveness of breast cancer. In other systems, inappropriate expression of a nonepithelial cadherin, such as N-cadherin, by an epithelial cell has been shown to downregulate E-cadherin expression and to contribute to a scattered phenotype. In this study, we explored the possibility that expression of nonepithelial cadherins may be correlated with increased motility and invasion in breast cancer cells. We show that N-cadherin promotes motility and invasion; that decreased expression of E-cadherin does not necessarily correlate with motility or invasion; that N-cadherin expression correlates both with invasion and motility, and likely plays a direct role in promoting motility; that forced expression of E-cadherin in invasive, N-cadherin–positive cells does not reduce their motility or invasive capacity; that forced expression of N-cadherin in noninvasive, E-cadherin–positive cells produces an invasive cell, even though these cells continue to express high levels of E-cadherin; that N-cadherin–dependent motility may be mediated by FGF receptor signaling; and that cadherin-11 promotes epithelial cell motility in a manner similar to N-cadherin.
Microtubule Interactions with the Cell Cortex Causing Nuclear Movements in Saccharomyces cerevisiae
Authors: Adames Neil R. , Cooper John A.
Published: July 2002

During mitosis in budding yeast the nucleus first moves to the mother-bud neck and then into the neck. Both movements depend on interactions of cytoplasmic microtubules with the cortex. We investigated the mechanism of these movements in living cells using video analysis of GFP-labeled microtubules in wild-type cells and in EB1 and Arp1 mutants, which are defective in the first and second steps, respectively. We found that nuclear movement to the neck is largely mediated by the capture of microtubule ends at one cortical region at the incipient bud site or bud tip, followed by microtubule depolymerization. Efficient microtubule interactions with the capture site require that microtubules be sufficiently long and dynamic to probe the cortex. In contrast, spindle movement into the neck is mediated by microtubule sliding along the bud cortex, which requires dynein and dynactin. Free microtubules can also slide along the cortex of both bud and mother. Capture/shrinkage of microtubule ends also contributes to nuclear movement into the neck and can serve as a backup mechanism to move the nucleus into the neck when microtubule sliding is impaired. Conversely, microtubule sliding can move the nucleus into the neck even when capture/shrinkage is impaired.
Normal Fertilization Occurs with Eggs Lacking the Integrin α6β1 and Is Cd9-Dependent
Authors: Miller Brent J. , Georges-Labouesse Elisabeth , Primakoff Paul , Myles Diana G.
Published: July 2002

Previous results, based on inhibition of fertilization by an anti–α6 integrin mAb (GoH3), suggest that the α6β1 integrin on mouse eggs functions as the receptor for sperm (Almeida, E.A., A.P. Huovila, A.E. Sutherland, L.E. Stephens, P.G. Calarco, L.M. Shaw, A.M. Mercurio, A. Sonnenberg, P. Primakoff, D.G. Myles, and J.M. White. 1995. Cell. 81:1095–1104). Because the egg surface tetraspanin CD9 is essential for gamete fusion (Kaji, K., S. Oda, T. Shikano, T. Ohnuki, Y. Uematsu, J. Sakagami, N. Tada, S. Miyazaki, and A. Kudo. 2000. Nat. Genet. 24:279–282; Le Naour, F., E. Rubinstein, C. Jasmin, M. Prenant, and C. Boucheix. 2000. Science. 287:319–321; Miyado, K., G. Yamada, S. Yamada, H. Hasuwa, Y. Nakamura, F. Ryu, K. Suzuki, K. Kosai, K. Inoue, A. Ogura, M. Okabe, and E. Mekada. 2000. Science. 287:321–324) and CD9 is known to associate with integrins, recent models of gamete fusion have posited that egg CD9 acts in association with α6β1 in fusion (Chen, M.S., K.S. Tung, S.A. Coonrod, Y. Takahashi, D. Bigler, A. Chang, Y. Yamashita, P.W. Kincade, J.C. Herr, and J.M. White. 1999. Proc. Natl. Acad. Sci. USA. 96:11830–11835; Kaji, K., S. Oda, T. Shikano, T. Ohnuki, Y. Uematsu, J. Sakagami, N. Tada, S. Miyazaki, and A. Kudo. 2000. Nat. Genet. 24:279–282; Le Naour, F., E. Rubinstein, C. Jasmin, M. Prenant, and C. Boucheix. 2000. Science. 287:319–321; Miyado, K., G. Yamada, S. Yamada, H. Hasuwa, Y. Nakamura, F. Ryu, K. Su- zuki, K. Kosai, K. Inoue, A. Ogura, M. Okabe, and E. Mekada. 2000. Science. 287:321–324). Using eggs from cultured ovaries of mice lacking the α6 integrin subunit, we found that the fertilization rate, fertilization index, and sperm binding were not impaired compared with wild-type or heterozygous controls. Furthermore, a reexamination of antibody inhibition, using an assay that better simulates in vivo fertilization conditions, revealed no inhibition of fusion by the GoH3 mAb. We also found that an anti-CD9 mAb completely blocks sperm fusion with either wild-type eggs or eggs lacking α6β1. Based on these results, we conclude that the α6β1 integrin is not essential for sperm–egg fusion, and we suggest a new model in which CD9 acts by itself, or interacts with egg protein(s) other than α6β1, to function in sperm–egg fusion.
A Kinesin-Related Protein, Krp180, Positions Prometaphase Spindle Poles during Early Sea Urchin Embryonic Cell Division
Authors: Rogers Gregory C. , Chui Kitty K. , Lee Edwin W. , Wedaman Karen P. , Sharp David J. , Holland Gina , Morris Robert L. , Scholey Jonathan M.
Published: July 2002

We have investigated the intracellular roles of an Xklp2-related kinesin motor, KRP180, in positioning spindle poles during early sea urchin embryonic cell division using quantitative, real-time analysis. Immunolocalization reveals that KRP180 concentrates on microtubules in the central spindle, but is absent from centrosomes. Microinjection of inhibitory antibodies and dominant negative constructs suggest that KRP180 is not required for the initial separation of spindle poles, but instead functions to transiently position spindle poles specifically during prometaphase.
Defects in Axonal Elongation and Neuronal Migration in Mice with Disrupted tau and map1b Genes
Authors: Takei Yosuke , Teng Junlin , Harada Akihiro , Hirokawa Nobutaka
Published: July 2002

Tau and MAP1B are the main members of neuronal microtubule-associated proteins (MAPs), the functions of which have remained obscure because of a putative functional redundancy (Harada, A., K. Oguchi, S. Okabe, J. Kuno, S. Terada, T. Ohshima, R. Sato-Yoshitake, Y. Takei, T. Noda, and N. Hirokawa. 1994. Nature. 369:488–491; Takei, Y., S. Kondo, A. Harada, S. Inomata, T. Noda, and N. Hirokawa. 1997. J. Cell Biol. 137:1615–1626). To unmask the role of these proteins, we generated double-knockout mice with disrupted tau and map1b genes and compared their phenotypes with those of single-knockout mice. In the analysis of mice with a genetic background of predominantly C57Bl/6J, a hypoplastic commissural axon tract and disorganized neuronal layering were observed in the brains of the tau+/+map1b−/− mice. These phenotypes are markedly more severe in tau−/−map1b−/− double mutants, indicating that tau and MAP1B act in a synergistic fashion. Primary cultures of hippocampal neurons from tau−/−map1b−/− mice showed inhibited axonal elongation. In these cells, a generation of new axons via bundling of microtubules at the neck of the growth cones appeared to be disturbed. Cultured cerebellar neurons from tau−/−map1b−/− mice showed delayed neuronal migration concomitant with suppressed neurite elongation. These findings indicate the cooperative functions of tau and MAP1B in vivo in axonal elongation and neuronal migration as regulators of microtubule organization.
A Novel Function for the Tumor Suppressor p16INK4a
Authors: Plath Thomas , Detjen Katharina , Welzel Martina , von Marschall Zofia , Murphy Derek , Schirner Michael , Wiedenmann Bertram , Rosewicz Stefan
Published: July 2002

The tumor suppressor gene p16INK4a inhibits the kinase activity of the cyclin-dependent kinase 4–6/cyclin D complexes and subsequent phosphorylation of critical substrates necessary for transit through the G1 phase of the cell cycle. Recent studies suggested that control of the G1/S boundary might not be the sole biological function of p16INK4a. We hypothesized that p16INK4a might influence hitherto unknown critical features of a malignant epithelial phenotype, such as anchorage dependence. Here we provide evidence that stable transfection of p16INK4a restitutes apoptosis induction upon loss of anchorage (anoikis) in a variety of human cancer cells. Anoikis in p16INK4a-transfected cells was evidenced by DNA fragmentation and poly(ADP-ribose) polymerase cleavage upon cultivation on polyhydroxyethylmethacrylate-coated dishes and was associated with suppression of anchorage-independent growth as well as complete loss of tumorigenicity. p16INK4a-mediated anoikis was due to selective transcriptional upregulation of the α5 integrin chain of the α5β1 fibronectin receptor as detected by FACS® analysis, immunoprecipitation, Northern blotting, and nuclear run-on assays. Addition of soluble fibronectin and inhibitory α5 antibodies to nonadherent cells completely abolished p16INK4a-mediated anoikis, whereas laminin was ineffective. Furthermore, antisense-induced downregulation of the α5 integrin chain in p16INK4a-transfected cells restored resistance to anoikis. These data suggest a novel functional interference between a cell cycle–regulating tumor suppressor gene and membrane-bound integrins, thus regulating a hallmark feature of an epithelial transformed phenotype: susceptibility to anoikis.
P53 Regulates Myogenesis by Triggering the Differentiation Activity of Prb
Authors: Porrello Alessandro , Cerone Maria Antonietta , Coen Sabrina , Gurtner Aymone , Fontemaggi Giulia , Cimino Letizia , Piaggio Giulia , Sacchi Ada , Soddu Silvia
Published: July 2002

The p53 oncosuppressor protein regulates cell cycle checkpoints and apoptosis, but increasing evidence also indicates its involvement in differentiation and development. We had previously demonstrated that in the presence of differentiation-promoting stimuli, p53-defective myoblasts exit from the cell cycle but do not differentiate into myocytes and myotubes. To identify the pathways through which p53 contributes to skeletal muscle differentiation, we have analyzed the expression of a series of genes regulated during myogenesis in parental and dominant–negative p53 (dnp53)-expressing C2C12 myoblasts. We found that in dnp53-expressing C2C12 cells, as well as in p53−/− primary myoblasts, pRb is hypophosphorylated and proliferation stops. However, these cells do not upregulate pRb and have reduced MyoD activity. The transduction of exogenous TP53 or Rb genes in p53-defective myoblasts rescues MyoD activity and differentiation potential. Additionally, in vivo studies on the Rb promoter demonstrate that p53 regulates the Rb gene expression at transcriptional level through a p53-binding site. Therefore, here we show that p53 regulates myoblast differentiation by means of pRb without affecting its cell cycle–related functions.
Rab27a Is Required for Regulated Secretion in Cytotoxic T Lymphocytes
Authors: Stinchcombe Jane C. , Barral Duarte C. , Mules Emilie H. , Booth Sarah , Hume Alistair N. , Machesky Laura M. , Seabra Miguel C. , Griffiths Gillian M.
Published: July 2002

Rab27a activity is affected in several mouse models of human disease including Griscelli (ashen mice) and Hermansky-Pudlak (gunmetal mice) syndromes. A loss of function mutation occurs in the Rab27a gene in ashen (ash), whereas in gunmetal (gm) Rab27a dysfunction is secondary to a mutation in the α subunit of Rab geranylgeranyl transferase, an enzyme required for prenylation and activation of Rabs. We show here that Rab27a is normally expressed in cytotoxic T lymphocytes (CTLs), but absent in ashen homozygotes (ash/ash). Cytotoxicity and secretion assays show that ash/ash CTLs are unable to kill target cells or to secrete granzyme A and hexosaminidase. By immunofluorescence and electron microscopy, we show polarization but no membrane docking of ash/ash lytic granules at the immunological synapse. In gunmetal CTLs, we show underprenylation and redistribution of Rab27a to the cytosol, implying reduced activity. Gunmetal CTLs show a reduced ability to kill target cells but retain the ability to secrete hexosaminidase and granzyme A. However, only some of the granules polarize to the immunological synapse, and many remain dispersed around the periphery of the CTLs. These results demonstrate that Rab27a is required in a final secretory step and that other Rab proteins also affected in gunmetal are likely to be involved in polarization of the granules to the immunological synapse.
Cadherin-mediated cell sorting not determined by binding or adhesion specificity
Authors: Niessen Carien M. , Gumbiner Barry M.
Published: July 2002

Cadherin adhesion molecules play important roles in the establishment of tissue boundaries. Cells expressing different cadherins sort out from each other in cell aggregation assays. To determine the contribution of cadherin binding and adhesion specificity to the sorting process, we examined the adhesion of cells to different purified cadherin proteins. Chinese hamster ovary cell lines expressing one of four different cadherins were allowed to bind to the purified cadherin extracellular domains of either human E-cadherin or Xenopus C-cadherin, and the specificity of adhesion was compared with cell-sorting assays. None of the different cadherin-expressing cells exhibited any adhesive specificity toward either of the two purified cadherin substrates, even though these cadherins differ considerably in their primary sequence. In addition, all cells exhibited similar strengthening of adhesion on both substrates. However, this lack of adhesive specificity did not determine whether different cadherin-expressing cells would sort from each other, and the tendency to sort was not predictable by the extent of sequence diversity in their extracellular domains. These results show that cadherins are far more promiscuous in their adhesive-binding capacity than had been expected and that the ability to sort out must be determined by mechanisms other than simple adhesive-binding specificity.
Drosophila Aurora A kinase is required to localize D-TACC to centrosomes and to regulate astral microtubules
Authors: Giet Régis , McLean Doris , Descamps Simon , Lee Michael J. , Raff Jordan W. , Prigent Claude , Glover David M.
Published: July 2002

Disruption of the function of the A-type Aurora kinase of Drosophila by mutation or RNAi leads to a reduction in the length of astral microtubules in syncytial embryos, larval neuroblasts, and cultured S2 cells. In neuroblasts, it can also lead to loss of an organized centrosome and its associated aster from one of the spindle poles, whereas the centrosome at the other pole has multiple centrioles. When centrosomes are present at the poles of aurA mutants or aurA RNAi spindles, they retain many antigens but are missing the Drosophila counterpart of mammalian transforming acidic coiled coil (TACC) proteins, D-TACC. We show that a subpopulation of the total Aurora A is present in a complex with D-TACC, which is a substrate for the kinase. We propose that one of the functions of Aurora A kinase is to direct centrosomal organization such that D-TACC complexed to the MSPS/XMAP215 microtubule-associated protein may be recruited, and thus modulate the behavior of astral microtubules.
Phosphoinositides and phagocytosis
Authors: Gillooly David J. , Simonsen Anne , Stenmark Harald
Published: July 2002

Phosphoinositide 3 kinases (PI3Ks)**Abbreviation used in this paper: PI3K, phosphoinositide 3 kinase. are known as regulators of phagocytosis. Recent results demonstrate that class I and III PI3Ks act consecutively in phagosome formation and maturation, and that their respective products, phosphatidylinositol 3,4,5-trisphosphate (PI[3,4,5]P3) and phosphatidylinositol 3-phosphate (PI[3]P), accumulate transiently at different stages. Phagosomes containing Mycobacterium tuberculosis do not acquire the PI(3)P-binding protein EEA1, which is required for phagosome maturation. This suggests a possible mechanism of how this microorganism evades degradation in phagolysosomes.
Ras and TGFβ cooperatively regulate epithelial cell plasticity and metastasis
Authors: Janda Elzbieta , Lehmann Kerstin , Killisch Iris , Jechlinger Martin , Herzig Michaela , Downward Julian , Beug Hartmut , Grünert Stefan
Published: July 2002

Multistep carcinogenesis involves more than six discrete events also important in normal development and cell behavior. Of these, local invasion and metastasis cause most cancer deaths but are the least well understood molecularly. We employed a combined in vitro/in vivo carcinogenesis model, that is, polarized Ha-Ras–transformed mammary epithelial cells (EpRas), to dissect the role of Ras downstream signaling pathways in epithelial cell plasticity, tumorigenesis, and metastasis. Ha-Ras cooperates with transforming growth factor β (TGFβ) to cause epithelial mesenchymal transition (EMT) characterized by spindle-like cell morphology, loss of epithelial markers, and induction of mesenchymal markers. EMT requires continuous TGFβ receptor (TGFβ-R) and oncogenic Ras signaling and is stabilized by autocrine TGFβ production. In contrast, fibroblast growth factors, hepatocyte growth factor/scatter factor, or TGFβ alone induce scattering, a spindle-like cell phenotype fully reversible after factor withdrawal, which does not involve sustained marker changes. Using specific inhibitors and effector-specific Ras mutants, we show that a hyperactive Raf/mitogen-activated protein kinase (MAPK) is required for EMT, whereas activation of phosphatidylinositol 3-kinase (PI3K) causes scattering and protects from TGFβ-induced apoptosis. Hyperactivation of the PI3K pathway or the Raf/MAPK pathway are sufficient for tumorigenesis, whereas EMT in vivo and metastasis required a hyperactive Raf/MAPK pathway. Thus, EMT seems to be a close in vitro correlate of metastasis, both requiring synergism between TGFβ-R and Raf/MAPK signaling.
Bloom's syndrome protein is required for correct relocalization of RAD50/MRE11/NBS1 complex after replication fork arrest
Authors: Franchitto Annapaola , Pichierri Pietro
Published: July 2002

Bloom's syndrome (BS) is a rare genetic disorder characterized by a broad range of symptoms and, most importantly, a predisposition to many types of cancers. Cells derived from patients with BS exhibit an elevated rate of somatic recombination and hypermutability, supporting a role for bleomycin (BLM) in the maintenance of genomic integrity. BLM is thought to participate in several DNA transactions, the failure of which could give raise to genomic instability, and to interact with many proteins involved in replication, recombination, and repair. In this study, we show that BLM function is specifically required to properly relocalize the RAD50/MRE11/NBS1 (RMN) complex at sites of replication arrest, but is not essential in the activation of BRCA1 either after stalled replication forks or γ-rays. We also provide evidence that BLM is phosphorylated after replication arrest in an Ataxia and RAD3-related protein (ATR)-dependent manner and that phosphorylation is not required for subnuclear relocalization. Therefore, in ATR dominant negative mutant cells, the assembly of the RMN complex in nuclear foci after replication blockage is almost completely abolished. Together, these results suggest a relationship between BLM, ATR, and the RMN complex in the response to replication arrest, proposing a role for BLM protein and RMN complex in the resolution of stalled replication forks.
Myosin-I nomenclature
Authors: Gillespie Peter G. , Albanesi Joseph P. , Bähler Martin , Bement William M. , Berg Jonathan S. , Burgess David R. , Burnside Beth , Cheney Richard E. , Corey David P. , Coudrier Evelyne , de Lanerolle Primal , Hammer John A. , Hasson Tama , Holt Jeffrey R. , Hudspeth A.J. , Ikebe Mitsuo , Kendrick-Jones John , Korn Edward D. , Li Rong , Mercer John A. , Milligan Ronald A. , Mooseker Mark S. , Ostap E. Michael , Petit Christine , Pollard Thomas D. , Sellers James R. , Soldati Thierry , Titus Margaret A.
Published: July 2002

We suggest that the vertebrate myosin-I field adopt a common nomenclature system based on the names adopted by the Human Genome Organization (HUGO). At present, the myosin-I nomenclature is very confusing; not only are several systems in use, but several different genes have been given the same name. Despite their faults, we believe that the names adopted by the HUGO nomenclature group for genome annotation are the best compromise, and we recommend universal adoption.
PECAM-1 (CD31) regulates a hydrogen peroxide–activated nonselective cation channel in endothelial cells
Authors: Ji Guangju , O'Brien Christopher D. , Feldman Morris , Manevich Yefim , Lim Poay , Sun Jing , Albelda Steven M. , Kotlikoff Michael I.
Published: July 2002

Hydrogen peroxide (H2O2) released by neutrophils is an important mediator of endothelial cell (EC) injury and vascular inflammation via its effect on EC-free Ca2+, [Ca2+]i. Although the underlying mechanisms are not well understood, platelet endothelial cell adhesion molecule (PECAM)-1/CD-31 is a critical modulator of neutrophil–EC transmigration. PECAM-1 is also known to regulate EC calcium signals and to undergo selective tyrosine phosphorylation. Here, we report that PECAM-1 molecules transduce EC responses to hydrogen peroxide. In human umbilical vein EC and REN cells (a PECAM-1–negative EC-like cell line) stably transfected with PECAM-1 (RHP), noncytolytic H2O2 exposure (100–200 μM H2O2) activated a calcium-permeant, nonselective cation current, and a transient rise in [Ca2+]i of similar time course. Neither response was observed in untransfected REN cells, and H2O2-evoked cation current was ablated in REN cells transfected with PECAM-1 constructs mutated in the cytoplasmic tyrosine–containing domain. The PECAM-dependent H2O2 current was inhibited by dialysis of anti–PECAM-1 cytoplasmic domain antibodies, required Src family tyrosine kinase activity, was independent of inositol trisphosphate receptor activation, and required only an intact PECAM-1 cytoplasmic domain. PECAM-1–dependent H2O2 currents and associated [Ca2+]i transients may play a significant role in regulating neutrophil–endothelial interaction, as well as in oxidant-mediated endothelial response and injury.
Fibroblast growth factor–specific modulation of cellular response by syndecan-4
Authors: Horowitz Arie , Tkachenko Eugene , Simons Michael
Published: July 2002

Proteoglycans participate in growth factor interaction with the cell surface through their heparan sulfate chains (HS), but it is not known if they are otherwise involved in growth factor signaling. It appears now that the syndecan-4 core protein, a transmembrane proteoglycan shown previously to bind phosphatidylinositol 4,5-bisphosphate (PIP2) and activate PKCα, participates in mediating the effects of fibroblast growth factor (FGF)2 on cell function. Mutations in the cytoplasmic tail of syndecan-4 that either reduced its affinity to PIP2 (PIP2−) or disrupted its postsynaptic density 95, disk large, zona occludens-1 (PDZ)-dependent binding (PDZ−) produced a FGF2-specific dominant negative phenotype in endothelial cells as evidenced by the marked decline of their migration and proliferation rates and the impairment of their capacity to form tubes. In both cases, the molecular mechanism was determined to consist of a decrease in the syndecan-4–dependent activation of PKCα. This decrease was caused either by inhibition of FGF2-induced syndecan-4 dephosphorylation in the case of the PDZ− mutation or by disruption of basolateral targeting of syndecan-4 and its associated PDZ-dependent complex in the case of the PIP2− mutation. These results suggest that PKCα activation and PDZ-mediated formation of a serine/threonine phosphatase-containing complex by syndecan-4 are downstream events of FGF2 signaling.
Preferential Interaction of a Novel Tumor Surface Protein (p38.5) with Naive Natural Killer Cells
Authors: Das Ballabh , Mondragon Mary O. , Tao Shi-Zhen , Norin Allen J.
Published: July 2002

A receptor–ligand interaction exclusive to natural killer (NK) cell–mediated recognition and triggering of tumor cell destruction has not yet been identified. In contrast, molecules that are involved in cellular adhesion and regulation of NK cytolysis have been well studied. In this report, a novel tumor surface protein is identified that exhibits characteristics of a recognition structure for naive NK cells. A tagged ligand–cell adsorption technique revealed a 38.5-kD plasma membrane protein (p38.5) from a prototypical NK-susceptible cell line (K562) that preferentially bound to NK cells (CD3−CD5−CD16+) relative to T lymphocytes (CD3+CD5+ CD16−). The molecule was purified to apparent homogeneity for further characterization. An amino acid sequence of an 11-mer internal peptide of p38.5 did not exhibit homology to known proteins. Affinity-purified antibody generated against this peptide (anti-p38.5) reacted with a single protein of 38.5 kD on Western blots of whole cell extracts of K562. Flow cytometry and immunoprecipitation studies of surface-labeled tumor cells demonstrated expression of p38.5 on NK-susceptible tumor cell lines (K562, MOLT-4, Jurkat), whereas p38.5 was not detected on NK-resistant tumor cell lines (A549, Raji, MDA-MB-231). Significantly, p38.5 loss variants derived from wild-type Jurkat and Molt-4 cell lines exhibited decreased susceptibility to NK cell–mediated lysis demonstrating a strong association between cell surface expression of p38.5 and cytotoxicity. Purified p38.5 retained preferential binding to NK cells and inhibited NK activity in a dose-dependent manner, thereby providing direct evidence of a role in the lytic process. Binding studies identified a 70-kD membrane protein from NK cells as a possible receptor for the p38.5 tumor ligand. Consistent with cellular adsorption studies, the 70-kD, p38.5 binding protein was not detected on T lymphocytes. Based on studies demonstrating selective binding of p38.5 to NK cells, lack of expression on NK-resistant tumor cell lines and ability of the purified molecule to block cytolysis, we conclude that p38.5 may serve as a recognition/triggering ligand for naive human NK cells.
Mutational Analysis of the Active Site and Antibody Epitopes of the Complement-inhibitory Glycoprotein, CD59
Authors: Bodian Dale L. , Davis Simon J. , Morgan B. Paul , Rushmere Neil K.
Published: July 2002

The Ly-6 superfamily of cell surface molecules includes CD59, a potent regulator of the complement system that protects host cells from the cytolytic action of the membrane attack complex (MAC). Although its mechanism of action is not well understood, CD59 is thought to prevent assembly of the MAC by binding to the C8 and/or C9 proteins of the nascent complex. Here a systematic, structure-based mutational approach has been used to determine the region(s) of CD59 required for its protective activity. Analysis of 16 CD59 mutants with single, highly nonconservative substitutions suggests that CD59 has a single active site that includes Trp-40, Arg-53, and Glu-56 of the glycosylated, membrane-distal face of the disk-like extracellular domain and, possibly, Asp-24 positioned at the edge of the domain. The putative active site includes residues conserved across species, consistent with the lack of strict homologous restriction previously observed in studies of CD59 function. Competition and mutational analyses of the epitopes of eight CD59-blocking and non-blocking monoclonal antibodies confirmed the location of the active site. Additional experiments showed that the expression and function of CD59 are both glycosylation independent.
Granzyme B (GraB) Autonomously Crosses the Cell Membrane and Perforin Initiates Apoptosis and GraB Nuclear Localization
Authors: Shi Lianfa , Mai Sabine , Israels Sara , Browne Kylie , Trapani Joseph A. , Greenberg Arnold H.
Published: July 2002

Granzyme B (GraB) induces apoptosis in the presence of perforin. Perforin polymerizes in the cell membrane to form a nonspecific ion pore, but it is not known where GraB acts to initiate the events that ultimately lead to apoptosis. It has been hypothesized that GraB enters the target cell through a perforin channel and then initiates apoptosis by cleaving and activating members of the ICE/Ced-3 family of cell death proteases. To determine if GraB can enter the cell, we treated YAC-1 or HeLa cells with FITC-labeled GraB and measured intracellular fluorescence with a high sensitivity CCD camera and image analyzer. GraB was internalized and found diffusely dispersed in the cell cytoplasm within 10 min. Uptake was inhibited at low temperature (4°C) and by pretreatment with metabolic inhibitors, NaF and DNP, or cytochalasin B, a drug that both blocks microfilament formation, and FITC-GraB remained on the cell membrane localized in patches. With the simultaneous addition of perforin and FITC-GraB, no significant increase in cytoplasmic fluorescence was observed over that found in cells treated only with FITC-GraB. However, FITC-GraB was now detected in the nucleus of apoptotic cells labeling apoptotic bodies and localized areas within and along the nuclear membrane. The ability of GraB to enter cells in the absence of perforin was reexamined using anti-GraB antibody immunogold staining of ultrathin cryosections of cells incubated with GraB. Within 15 min, gold particles were detected both on the plasma membrane and in the cytoplasm of cells with some gold staining adjacent to the nuclear envelope but not in the nucleus. Cells internalizing GraB in the absence of perforin appeared morphologically normal by Hoechst staining and electron microscopy. GraB directly microinjected into the cytoplasm of B16 melanoma cells induced transient plasma membrane blebbing and nuclear coarsening but the cells did not become frankly apoptotic unless perforin was added. We conclude that GraB can enter cells autonomously but that perforin initiates the apoptotic process and the entry of GraB into the nucleus.
Chronic Tumor Necrosis Factor Alters T Cell Responses by Attenuating T Cell Receptor Signaling
Authors: Cope Andrew P. , Liblau Roland S. , Yang Xiao-Dong , Congia Mauro , Laudanna Carlo , Schreiber Robert D. , Probert Lesley , Kollias George , McDevitt Hugh O.
Published: July 2002

Repeated injections of adult mice with recombinant murine TNF prolong the survival of NZB/W F1 mice, and suppress type I insulin-dependent diabetes mellitus (IDDM) in nonobese diabetic (NOD) mice. To determine whether repeated TNF injections suppress T cell function in adult mice, we studied the responses of influenza hemagglutinin-specific T cells derived from T cell receptor (HNT-TCR) transgenic mice. Treatment of adult mice with murine TNF for 3 wk suppressed a broad range of T cell responses, including proliferation and cytokine production. Furthermore, T cell responses of HNT-TCR transgenic mice also expressing the human TNF-globin transgene were markedly reduced compared to HNT-TCR single transgenic littermates, indicating that sustained p55 TNF-R signaling is sufficient to suppress T cell function in vivo. Using a model of chronic TNF exposure in vitro, we demonstrate that (a) chronic TNF effects are dose and time dependent, (b) TNF suppresses the responses of both Th1 and Th2 T helper subsets, (c) the suppressive effects of endogenous TNF produced in T cell cultures could be reversed with neutralizing monoclonal antibodies to TNF, and (d) prolonged TNF exposure attenuates T cell receptor signaling. The finding that anti-TNF treatment in vivo enhances T cell proliferative responses and cytokine production provides evidence for a novel regulatory effect of TNF on T cells in healthy laboratory mice. These effects are more pronounced in chronic inflammatory disease. In addition, our data provide a mechanism through which prolonged TNF exposure suppresses disease in animal models of autoimmunity.
Identification of a DNA Segment Exhibiting Rearrangement Modifying Effects upon Transgenic δ-deleting Elements
Authors: Janowski Karen M. , Ledbetter Stephanie , Mayo Matthew S. , Hockett Richard D.
Published: July 2002

Control of the rearrangement and expression of the T cell receptor α and δ chains is critical for determining T cell type. The process of δ deletion is a candidate mechanism for maintaining separation of the α and δ loci. Mice harboring a transgenic reporter δ deletion construct show α/β T cell lineage–specific use of the transgenic elements. A 48-basepair segment of DNA, termed HPS1A, when deleted from this reporter construct, loses tight lineage-specific rearrangement control of transgenic elements, with abundant rearrangements of transgenic δ-deleting elements now in γ/δ T cells. Furthermore, HPS1A augments recombination frequency of extrachromosomal substrates in an in vitro recombination assay. DNA binding proteins recognizing HPS1A have been identified and are restricted to early B and T cells, during the time of active rearrangement of endogenous TCR and immunoglobulin loci. These data are consistent with δ deletion playing an important role in maintaining separate TCR α and δ loci.
Characterization of an Adhesion Molecule that Mediates Leukocyte Rolling on 24 h Cytokine- or Lipopolysaccharide-stimulated Bovine Endothelial Cells under Flow Conditions
Authors: Jutila Mark A. , Wilson Eric , Kurk Sandy
Published: July 2002

Bovine γ/δ T cells and neutrophils roll on 24 h cytokine- or lipopolysaccharide-stimulated bovine fetal umbilical cord endothelial cells in assays done under physiological flow. An antibody directed against E- and L-selectin has minimal blocking effect on this rolling interaction. mAbs were raised against the stimulated bovine endothelial cells and screened for inhibition of γ/δ T cell rolling. One mAb (GR113) was identified that recognizes an antigen (GR antigen) selectively expressed by stimulated bovine endothelial cells isolated from fetal umbilical cord, mesenteric lymph nodes, and aorta. GR113 blocked bovine γ/δ T cell as well as neutrophil rolling on the 24 h-activated endothelial cells. The GR antigen was constitutively expressed at low levels on the cell surface of platelets and its expression was not upregulated after stimulation of these cells with thrombin or phorbol myristate acetate. However, stimulated platelets released a soluble, functionally active form of the molecule that selectively bound in solution to γ/δ T cells in a mixed lymphocyte preparation. GR113 mAb blocked the binding of the soluble platelet molecule to the γ/δ T cells. Soluble GR antigen also bound a subset of human lymphocytes. Cutaneous lymphocyte-associated antigen (CLA) bright human lymphocytes exhibited the greatest capacity to bind the GR antigen, though CLA was not required for binding. Subsets of both human CD4 and CD8 T cells bound the GR antigen. Immunoprecipitation experiments showed the GR antigen to be 110-120 kD Mr. The binding of soluble GR antigen was inhibited by EDTA and O-sialoglycoprotease, but not neuraminidase treatment of the target cells.
Signal Transduction Due to HIV-1 Envelope Interactions with Chemokine Receptors CXCR4 or CCR5
Authors: Davis Craig B. , Dikic Ivan , Unutmaz Derya , Hill C. Mark , Arthos James , Siani Michael A. , Thompson Darren A. , Schlessinger Joseph , Littman Dan R.
Published: July 2002

Infection with HIV-1 requires expression of CD4 and the chemokine receptors CXCR4 or CCR5 at the target cell surface. Engagement of these receptors by the HIV-1 envelope glycoprotein is essential for membrane fusion, but may additionally activate intracellular signaling pathways. In this study, we demonstrate that chemokines and HIV-1 envelope glycoproteins from both T-tropic and macrophage-tropic strains rapidly induce tyrosine phosphorylation of the protein tyrosine kinase Pyk2. The response requires CXCR4 and CCR5 to be accessible on the cell surface. The results presented here provide the first evidence for activation of an intracellular signaling event that can initiate multiple signaling pathways as a consequence of contact between HIV-1 and chemokine receptors.
TRANCE (Tumor Necrosis Factor [TNF]-related Activation-induced Cytokine), a New TNF Family Member Predominantly Expressed in T cells, Is a Dendritic Cell–specific Survival Factor
Authors: Wong Brian R. , Josien Régis , Lee Soo Young , Sauter Birthe , Li Hong-Li , Steinman Ralph M. , Choi Yongwon
Published: July 2002

TRANCE (tumor necrosis factor [TNF]–related activation-induced cytokine) is a new member of the TNF family that is induced upon T cell receptor engagement and activates c-Jun N-terminal kinase (JNK) after interaction with its putative receptor (TRANCE-R). In addition, TRANCE expression is restricted to lymphoid organs and T cells. Here, we show that high levels of TRANCE-R are detected on mature dendritic cells (DCs) but not on freshly isolated B cells, T cells, or macrophages. Signaling by TRANCE-R appears to be dependent on TNF receptor–associated factor 2 (TRAF2), since JNK induction is impaired in cells from transgenic mice overexpressing a dominant negative TRAF2 protein. TRANCE inhibits apoptosis of mouse bone marrow–derived DCs and human monocyte-derived DCs in vitro. The resulting increase in DC survival is accompanied by a proportional increase in DC-mediated T cell proliferation in a mixed leukocyte reaction. TRANCE upregulates Bcl-xL expression, suggesting a potential mechanism for enhanced DC survival. TRANCE does not induce the proliferation of or increase the survival of T or B cells. Therefore, TRANCE is a new DC-restricted survival factor that mediates T cell–DC communication and may provide a tool to selectively enhance DC activity.
Nitric Oxide Primes Pancreatic β Cells for Fas-mediated Destruction in Insulin-dependent Diabetes Mellitus
Authors: Stassi Giorgio , Maria Ruggero De , Trucco Giuliana , Rudert William , Testi Roberto , Galluzzo Aldo , Giordano Carla , Trucco Massimo
Published: July 2002

Fas is an apoptosis-inducing surface receptor involved in controlling tissue homeostasis and function at multiple sites. Here we show that β cells from the pancreata of newly diagnosed insulin-dependent diabetes mellitus (IDDM) patients express Fas and show extensive apoptosis among those cells located in proximity to Fas ligand–expressing T lymphocytes infiltrating the IDDM islets. Normal human pancreatic β cells that do not constitutively express Fas, become strongly Fas positive after interleuken (IL)-1β exposure, and are then susceptible to Fas-mediated apoptosis. NG-monomethyl-l-arginine, an inhibitor of nitric oxide (NO) synthase, prevents IL-1β–induced Fas expression, whereas the NO donors sodium nitroprusside and nitric oxide releasing compound (NOC)-18, induce functional Fas expression in normal pancreatic β cells. These findings suggest that NO-mediated upregulation of Fas contributes to pancreatic β cell damage in IDDM.
Antigen Presentation by Dendritic Cells after Immunization with DNA Encoding a Major Histocompatibility Complex Class II–restricted Viral Epitope
Authors: Casares Sofia , Inaba Kayo , Brumeanu Teodor-Doru , Steinman Ralph M. , Bona Constantin A.
Published: July 2002

Intramuscular and intracutaneous immunization with naked DNA can vaccinate animals to the encoded proteins, but the underlying mechanisms of antigen presentation are unclear. We used DNA that encodes an A/PR/8/34 influenza peptide for CD4 T cells and that elicits protective antiviral immunity. DNA-transfected, cultured muscle cells released the influenza polypeptide, which then could be presented on the major histocompatibility complex class II molecules of dendritic cells. When DNA was injected into muscles or skin, and antigen-presenting cells were isolated from either the draining lymph nodes or the skin, dendritic, but not B, cells presented antigen to T cells and carried plasmid DNA. We suggest that the uptake of DNA and/or the protein expressed by dendritic cells triggers immune responses to DNA vaccines.
CD4 Regulates Susceptibility to Fas ligand– and Tumor Necrosis Factor–mediated Apoptosis
Authors: Algeciras Alicia , Dockrell David H. , Lynch David H. , Paya Carlos V.
Published: July 2002

The current knowledge of CD4 function is limited to its role as a necessary coreceptor in TCR-initiated signaling. We have investigated whether CD4 regulates additional T cell functions. Using human primary resting CD4+ T cells, we demonstrate that CD4 activation is sufficient to induce lymphocyte death. Immediately after CD4 cross-linking, CD4+ T cells are rendered susceptible to apoptosis mediated by TNF or FasL. This, together with the concomitant induction of FasL within the same population, results in significant CD4+ T cell death in vitro. The CD4-dependent induction of susceptibility to apoptosis that is mediated by TNF or FasL is protein synthesis independent but phosphorylation dependent. After CD4 activation, PKC regulates susceptibility to apoptosis mediated by FasL but not the induction of susceptibility to TNF-dependent apoptosis. Moreover, significant differences between CD3 and CD4 activation were observed with regards to the kinetics of induction of CD4+ T cell susceptibility to FasL- and TNF-mediated apoptosis. Altogether, these results provide a model with which to study the molecular mechanisms regulating lymphocyte survival after CD4 activation, and highlight the potential role of CD4 in controlling lymphocyte apoptosis under physiological conditions or in disease states such as HIV infection.
The Permeability Transition Pore Complex: A Target for Apoptosis Regulation by Caspases and Bcl-2–related Proteins
Authors: Marzo Isabel , Brenner Catherine , Zamzami Naoufal , Susin Santos A. , Beutner Gisela , Brdiczka Dieter , Rémy René , Xie Zhi-Hua , Reed John C. , Kroemer Guido
Published: July 2002

Early in programmed cell death (apoptosis), mitochondrial membrane permeability increases. This is at least in part due to opening of the permeability transition (PT) pore, a multiprotein complex built up at the contact site between the inner and the outer mitochondrial membranes. The PT pore has been previously implicated in clinically relevant massive cell death induced by toxins, anoxia, reactive oxygen species, and calcium overload. Here we show that PT pore complexes reconstituted in liposomes exhibit a functional behavior comparable with that of the natural PT pore present in intact mitochondria. The PT pore complex is regulated by thiol-reactive agents, calcium, cyclophilin D ligands (cyclosporin A and a nonimmunosuppressive cyclosporin A derivative), ligands of the adenine nucleotide translocator, apoptosis-related endoproteases (caspases), and Bcl-2–like proteins. Although calcium, prooxidants, and several recombinant caspases (caspases 1, 2, 3, 4, and 6) enhance the permeability of PT pore-containing liposomes, recombinant Bcl-2 or Bcl-XL augment the resistance of the reconstituted PT pore complex to pore opening. Mutated Bcl-2 proteins that have lost their cytoprotective potential also lose their PT modulatory capacity. In conclusion, the PT pore complex may constitute a crossroad of apoptosis regulation by caspases and members of the Bcl-2 family.