bluuebunny/crossref_metadata_2025 huggingface dataset:
The Triad Targeting Signal of the Skeletal Muscle Calcium Channel Is Localized in the Cooh Terminus of the α1S Subunit
Authors: Flucher Bernhard E. , Kasielke Nicole , Grabner Manfred
Published: July 2002

The specific localization of L-type Ca2+ channels in skeletal muscle triads is critical for their normal function in excitation–contraction (EC) coupling. Reconstitution of dysgenic myotubes with the skeletal muscle Ca2+ channel α1S subunit restores Ca2+ currents, EC coupling, and the normal localization of α1S in the triads. In contrast, expression of the neuronal α1A subunit gives rise to robust Ca2+ currents but not to triad localization. To identify regions in the primary structure of α1S involved in the targeting of the Ca2+ channel into the triads, chimeras of α1S and α1A were constructed, expressed in dysgenic myotubes, and their subcellular distribution was analyzed with double immunofluorescence labeling of the α1S/α1A chimeras and the ryanodine receptor. Whereas chimeras containing the COOH terminus of α1A were not incorporated into triads, chimeras containing the COOH terminus of α1S were correctly targeted. Mapping of the COOH terminus revealed a triad-targeting signal contained in the 55 amino-acid sequence (1607–1661) proximal to the putative clipping site of α1S. Transferring this triad targeting signal to α1A was sufficient for targeting and clustering the neuronal isoform into skeletal muscle triads and caused a marked restoration of Ca2+-dependent EC coupling.
Apical, Lateral, and Basal Polarization Cues Contribute to the Development of the Follicular Epithelium during Drosophila Oogenesis
Authors: Tanentzapf Guy , Smith Christian , McGlade Jane , Tepass Ulrich
Published: July 2002

Analysis of the mechanisms that control epithelial polarization has revealed that cues for polarization are mediated by transmembrane proteins that operate at the apical, lateral, or basal surface of epithelial cells. Whereas for any given epithelial cell type only one or two polarization systems have been identified to date, we report here that the follicular epithelium in Drosophila ovaries uses three different polarization mechanisms, each operating at one of the three main epithelial surface domains. The follicular epithelium arises through a mesenchymal–epithelial transition. Contact with the basement membrane provides an initial polarization cue that leads to the formation of a basal membrane domain. Moreover, we use mosaic analysis to show that Crumbs (Crb) is required for the formation and maintenance of the follicular epithelium. Crb localizes to the apical membrane of follicle cells that is in contact with germline cells. Contact to the germline is required for the accumulation of Crb in follicle cells. Discs Lost (Dlt), a cytoplasmic PDZ domain protein that was shown to interact with the cytoplasmic tail of Crb, overlaps precisely in its distribution with Crb, as shown by immunoelectron microscopy. Crb localization depends on Dlt, whereas Dlt uses Crb-dependent and -independent mechanisms for apical targeting. Finally, we show that the cadherin–catenin complex is not required for the formation of the follicular epithelium, but only for its maintenance. Loss of cadherin-based adherens junctions caused by armadillo (β-catenin) mutations results in a disruption of the lateral spectrin and actin cytoskeleton. Also Crb and the apical spectrin cytoskeleton are lost from armadillo mutant follicle cells. Together with previous data showing that Crb is required for the formation of a zonula adherens, these findings indicate a mutual dependency of apical and lateral polarization mechanisms.
Distinct Protein Sorting and Localization to Premelanosomes, Melanosomes, and Lysosomes in Pigmented Melanocytic Cells✪
Authors: Raposo Graça , Tenza Danielle , Murphy Diane M. , Berson Joanne F. , Marks Michael S.
Published: July 2002

Melanosomes and premelanosomes are lysosome-related organelles with a unique structure and cohort of resident proteins. We have positioned these organelles relative to endosomes and lysosomes in pigmented melanoma cells and melanocytes. Melanosome resident proteins Pmel17 and TRP1 localized to separate vesicular structures that were distinct from those enriched in lysosomal proteins. In immunogold-labeled ultrathin cryosections, Pmel17 was most enriched along the intralumenal striations of premelanosomes. Increased pigmentation was accompanied by a decrease in Pmel17 and by an increase in TRP1 in the limiting membrane. Both proteins were largely excluded from lysosomal compartments enriched in LAMP1 and cathepsin D. By kinetic analysis of fluid phase uptake and immunogold labeling, premelanosomal proteins segregated from endocytic markers within an unusual endosomal compartment. This compartment contained Pmel17, was accessed by BSA–gold after 15 min, was acidic, and displayed a cytoplasmic planar coat that contained clathrin. Our results indicate that premelanosomes and melanosomes represent a distinct lineage of organelles, separable from conventional endosomes and lysosomes within pigmented cells. Furthermore, they implicate an unusual clathrin-coated endosomal compartment as a site from which proteins destined for premelanosomes and lysosomes are sorted.
Comparisons of CapG and gelsolin-null macrophages
Authors: Witke Walter , Li Wei , Kwiatkowski David J. , Southwick Frederick S.
Published: July 2002

Capping the barbed ends of actin filaments is a critical step for regulating actin-based motility in nonmuscle cells. The in vivo function of CapG, a calcium-sensitive barbed end capping protein and member of the gelsolin/villin family, has been assessed using a null Capg allele engineered into mice. Both CapG-null mice and CapG/gelsolin double-null mice appear normal and have no gross functional abnormalities. However, the loss of CapG in bone marrow macrophages profoundly inhibits macrophage colony stimulating factor–stimulated ruffling; reintroduction of CapG protein by microinjection fully restores this function. CapG-null macrophages also demonstrate ∼50% impairment of immunoglobulin G, and complement-opsonized phagocytosis and lanthanum-induced vesicle rocketing. These motile functions are not impaired in gelsolin-null macrophages and no additive effects are observed in CapG/gelsolin double-null macrophages, establishing that CapG function is distinct from, and does not overlap with, gelsolin in macrophages. Our observations indicate that CapG is required for receptor-mediated ruffling, and that it is a major functional component of macrophage phagocytosis. These primary effects on macrophage motile function suggest that CapG may be a useful target for the regulation of macrophage-mediated inflammatory responses.
Role of phosphatidylinositol 3-kinase and Rab5 effectors in phagosomal biogenesis and mycobacterial phagosome maturation arrest
Authors: Fratti Rutilio A. , Backer Jonathan M. , Gruenberg Jean , Corvera Silvia , Deretic Vojo
Published: July 2002

Phagosomal biogenesis is a fundamental biological process of particular significance for the function of phagocytic and antigen-presenting cells. The precise mechanisms governing maturation of phagosomes into phagolysosomes are not completely understood. Here, we applied the property of pathogenic mycobacteria to cause phagosome maturation arrest in infected macrophages as a tool to dissect critical steps in phagosomal biogenesis. We report the requirement for 3-phosphoinositides and acquisition of Rab5 effector early endosome autoantigen (EEA1) as essential molecular events necessary for phagosomal maturation. Unlike the model phagosomes containing latex beads, which transiently recruited EEA1, mycobacterial phagosomes excluded this regulator of vesicular trafficking that controls membrane tethering and fusion processes within the endosomal pathway and is recruited to endosomal membranes via binding to phosphatidylinositol 3-phosphate (PtdIns[3]P). Inhibitors of phosphatidylinositol 3′(OH)-kinase (PI-3K) activity diminished EEA1 recruitment to newly formed latex bead phagosomes and blocked phagosomal acquisition of late endocytic properties, indicating that generation of PtdIns(3)P plays a role in phagosomal maturation. Microinjection into macrophages of antibodies against EEA1 and the PI-3K hVPS34 reduced acquisition of late endocytic markers by latex bead phagosomes, demonstrating an essential role of these Rab5 effectors in phagosomal biogenesis. The mechanism of EEA1 exclusion from mycobacterial phagosomes was investigated using mycobacterial products. Coating of latex beads with the major mycobacterial cell envelope glycosylated phosphatidylinositol lipoarabinomannan isolated from the virulent Mycobacterium tuberculosis H37Rv, inhibited recruitment of EEA1 to latex bead phagosomes, and diminished their maturation. These findings define the generation of phosphatidylinositol 3-phosphate and EEA1 recruitment as: (a) important regulatory events in phagosomal maturation and (b) critical molecular targets affected by M. tuberculosis. This study also identifies mycobacterial phosphoinositides as products with specialized toxic properties, interfering with discrete trafficking stages in phagosomal maturation.
Ablation of Cypher, a PDZ-LIM domain Z-line protein, causes a severe form of congenital myopathy
Authors: Zhou Qiang , Chu Po-Hsien , Huang Chenqun , Cheng Ching-Feng , Martone Maryann E. , Knoll Gudrun , Shelton G. Diane , Evans Sylvia , Chen Ju
Published: July 2002

Cypher is a member of a recently emerging family of proteins containing a PDZ domain at their NH2 terminus and one or three LIM domains at their COOH terminus. Cypher knockout mice display a severe form of congenital myopathy and die postnatally from functional failure in multiple striated muscles. Examination of striated muscle from the mutants revealed that Cypher is not required for sarcomerogenesis or Z-line assembly, but rather is required for maintenance of the Z-line during muscle function. In vitro studies demonstrated that individual domains within Cypher localize independently to the Z-line via interactions with α-actinin or other Z-line components. These results suggest that Cypher functions as a linker-strut to maintain cytoskeletal structure during contraction.
Myogenic cell proliferation and generation of a reversible tumorigenic phenotype are triggered by preirradiation of the recipient site
Authors: Morgan Jennifer E. , Gross Jacqueline G. , Pagel Charles N. , Beauchamp Jonathan R. , Fassati Ariberto , Thrasher Adrian J. , Di Santo James P. , Fisher Ivan B. , Shiwen Xu , Abraham David J. , Partridge Terence A.
Published: July 2002

Environmental influences have profound yet reversible effects on the behavior of resident cells. Earlier data have indicated that the amount of muscle formed from implanted myogenic cells is greatly augmented by prior irradiation (18 Gy) of the host mouse muscle. Here we confirm this phenomenon, showing that it varies between host mouse strains. However, it is unclear whether it is due to secretion of proliferative factors or reduction of antiproliferative agents. To investigate this further, we have exploited the observation that the immortal myogenic C2 C12 cell line forms tumors far more rapidly in irradiated than in nonirradiated host muscle. We show that the effect of preirradiation on tumor formation is persistent and dose dependent. However, C2 C12 cells are not irreversibly compelled to form undifferentiated tumor cells by the irradiated muscle environment and are still capable of forming large amounts of muscle when reimplanted into a nonirradiated muscle. In a clonal analysis of this effect, we discovered that C2 C12 cells have a bimodal propensity to form tumors; some clones form no tumors even after extensive periods in irradiated graft sites, whereas others rapidly form extensive tumors. This illustrates the subtle interplay between the phenotype of implanted cells and the factors in the muscle environment.
DAP kinase and DRP-1 mediate membrane blebbing and the formation of autophagic vesicles during programmed cell death
Authors: Inbal Boaz , Bialik Shani , Sabanay Ilana , Shani Gidi , Kimchi Adi
Published: July 2002

Death-associated protein kinase (DAPk) and DAPk-related protein kinase (DRP)-1 proteins are Ca+2/calmodulin–regulated Ser/Thr death kinases whose precise roles in programmed cell death are still mostly unknown. In this study, we dissected the subcellular events in which these kinases are involved during cell death. Expression of each of these DAPk subfamily members in their activated forms triggered two major cytoplasmic events: membrane blebbing, characteristic of several types of cell death, and extensive autophagy, which is typical of autophagic (type II) programmed cell death. These two different cellular outcomes were totally independent of caspase activity. It was also found that dominant negative mutants of DAPk or DRP-1 reduced membrane blebbing during the p55/tumor necrosis factor receptor 1–induced type I apoptosis but did not prevent nuclear fragmentation. In addition, expression of the dominant negative mutant of DRP-1 or of DAPk antisense mRNA reduced autophagy induced by antiestrogens, amino acid starvation, or administration of interferon-γ. Thus, both endogenous DAPk and DRP-1 possess rate-limiting functions in these two distinct cytoplasmic events. Finally, immunogold staining showed that DRP-1 is localized inside the autophagic vesicles, suggesting a direct involvement of this kinase in the process of autophagy.
Extramedullary Expansion of Hematopoietic Progenitor Cells in Interleukin (IL)-6–sIL-6R Double Transgenic Mice
Authors: Peters Malte , Schirmacher Peter , Goldschmitt Jutta , Odenthal Margarete , Peschel Christian , Fattori Elena , Ciliberto Gennaro , Dienes Hans-Peter , Büschenfelde Karl-Hermann Meyer zum , Rose-John Stefan
Published: July 2002

Soluble cytokine receptors modulate the activity of their cognate ligands. Interleukin (IL)-6 in association with the soluble IL-6 receptor (sIL-6R) can activate cells expressing the gp130 signal transducer lacking the specific IL-6R. To investigate the function of the IL-6–sIL-6R complex in vivo and to discriminate the function of the IL-6–sIL-6R complex from the function of IL-6 alone, we have established a transgenic mouse model. Double-transgenic mice coexpressing IL-6 and sIL-6R were generated and compared with IL-6 and sIL-6R single-transgenic mice. The main phenotype found in IL-6–sIL-6R mice was a dramatic increase of extramedullary hematopoietic progenitor cells in liver and spleen but not in the bone marrow. In IL-6 single-transgenic mice and sIL-6R single-transgenic mice no such effects were observed. The high numbers of hematopoietic progenitor cells were reflected by a strong increase of peripheral blood cell numbers. Therefore, activators of the gp130 signal transducer like the IL-6–IL-6R complex may represent most powerful stimulators for extramedullary hematopoietic progenitor cells. gp130 activators may become important for the expansion of hematopoietic progenitor cells in vivo and in vitro.
Nonmitogenic Anti-CD3 Monoclonal Antibodies Deliver a Partial T Cell Receptor Signal and Induce Clonal Anergy
Authors: Smith Judith A. , Tso J. Yun , Clark Marcus R. , Cole Michael S. , Bluestone Jeffrey A.
Published: July 2002

Anti-CD3 monoclonal antibodies (mAbs) are potent immunosuppressive agents used in clinical transplantation. However, the activation-related adverse side effects associated with these mAbs have prompted the development of less toxic nonmitogenic anti-CD3 mAb therapies. At present, the functional and biochemical consequences of T cell exposure to nonmitogenic anti-CD3 is unclear. In this study, we have examined the early signaling events triggered by a nonmitogenic anti-CD3 mAb. Like the mitogenic anti-CD3 mAb, nonmitogenic anti-CD3 triggered changes in the T cell receptor (TCR) complex, including ζ chain tyrosine phosphorylation and ZAP-70 association. However, unlike the mitogenic anti-CD3 stimulation, nonmitogenic anti-CD3 was ineffective at inducing the highly phosphorylated form of ζ (p23) and tyrosine phosphorylation of the associated ZAP-70 tyrosine kinase. This proximal signaling deficiency correlated with minimal phospholipase Cγ-1 phosphorylation and failure to mobilize detectable Ca2+. Not only did biochemical signals delivered by nonmitogenic anti-CD3 resemble altered peptide ligand signaling, but exposure of Th1 clones to nonmitogenic anti-CD3 also resulted in functional anergy. Finally, a bispecific anti-CD3 × anti-CD4 F(ab)′2 reconstituted early signal transduction events and induced proliferation, suggesting that defective association of lck with the TCR complex may underlie the observed signaling differences between the mitogenic and nonmitogenic anti-CD3.
The α Chemokine, Interleukin 8, Inhibits the Antiviral Action of Interferon α
Authors: Khabar Khalid S.A. , Al-Zoghaibi Fahad , Al-Ahdal Mohammed N. , Murayama Tsugiya , Dhalla Mohammed , Mukaida Naofumi , Taha Mohammed , Al-Sedairy Sultan T. , Siddiqui Yunus , Kessie George , Matsushima Kouji
Published: July 2002

Interferon (IFN) exhibits a potent antiviral activity in vitro and plays a major role in the early defense against viruses. Like IFN, the proinflammatory chemokine, interleukin (IL)-8, is induced by viruses and appears in circulation during viral infections. In an in vitro cytopathic effect assay for IFN, we found that IL-8 can inhibit IFN-α activity in a dose-dependent manner. This action was reversed by specific monoclonal antibodies to IL-8. The chemokine was able to attenuate the IFN-mediated inhibition of viral replication as determined by measuring infectious virus yield. IL-8 also diminished the ability of IFN to inhibit an early stage of viral replication since IL-8 attenuated the inhibition of the formation of viral proteins. It appeared that IL-8 interfered with a late rather than an early step of IFN-mediated pathway such as early gene expression. The IL-8 inhibitory action on IFN-α antiviral activity was associated with reduced 2′,5′-A oligoadenylate synthetase activity, a pathway well correlative with the anti– encephalomyocarditis virus action of IFN-α. Understanding pathways that antagonize IFN action may lead to novel approaches to potentiate endogenous and therapeutic IFN.
Murine Macrophages Secrete Interferon γ upon Combined Stimulation with Interleukin (IL)-12 and IL-18: A Novel Pathway of Autocrine Macrophage Activation
Authors: Munder Markus , Mallo Moisés , Eichmann Klaus , Modolell Manuel
Published: July 2002

Interferon (IFN)-γ, a key immunoregulatory cytokine, has been thought to be produced solely by activated T cells and natural killer cells. In this study, we show that murine bone marrow– derived macrophages (BMMΦ) secrete large amounts of IFN-γ upon appropriate stimulation. Although interleukin (IL)-12 and IL-18 alone induce low levels of IFN-γ mRNA transcripts, the combined stimulation of BMMΦ with both cytokines leads to the efficient production of IFN-γ protein. The macrophage-derived IFN-γ is biologically active as shown by induction of inducible nitric oxide synthase as well as upregulation of CD40 in macrophages. Our findings uncover a novel pathway of autocrine macrophage activation by demonstrating that the macrophage is not only a key cell type responding to IFN-γ but also a potent IFN-γ–producing cell.
Cloning of  Vascular Adhesion Protein 1 Reveals a Novel Multifunctional Adhesion Molecule
Authors: Smith David J. , Salmi Marko , Bono Petri , Hellman Jukka , Leu Taina , Jalkanen Sirpa
Published: July 2002

Vascular adhesion protein 1 (VAP-1) is a human endothelial sialoglycoprotein whose cell surface expression is induced under inflammatory conditions. It has been shown previously to participate in lymphocyte recirculation by mediating the binding of lymphocytes to peripheral lymph node vascular endothelial cells in an L-selectin–independent fashion. We report here that the VAP-1 cDNA encodes a type II transmembrane protein of 84.6 kD with a single transmembrane domain located at the NH2-terminal end of the molecule and six potential N-glycosylation sites in the extracellular domain. In vivo, the protein exists predominantly as a homodimer of 170–180 kD. Ax endothelial cells transfected with a VAP-1 cDNA express VAP-1 on their cell surface and bind lymphocytes, and the binding can be partially inhibited with anti–VAP-1 mAbs. VAP-1 has no similarity to any currently known adhesion molecules, but has significant identity to the copper-containing amine oxidase family and has a monoamine oxidase activity. We propose that VAP-1 is a novel type of adhesion molecule with dual function. With the appropriate glycosylation and in the correct inflammatory setting, its expression on the lumenal endothelial cell surface allows it to mediate lymphocyte adhesion and to function as an adhesion receptor involved in lymphocyte recirculation. Its primary function in other locations where it is expressed, such as smooth muscle, may depend on its inherent monoamine oxidase activity.
Host Resistance to Intracellular Infection: Mutation of Natural Resistance-associated Macrophage Protein 1 (Nramp1) Impairs Phagosomal Acidification
Authors: Hackam David J. , Rotstein Ori D. , Zhang Wei-jian , Gruenheid Samantha , Gros Philippe , Grinstein Sergio
Published: July 2002

The mechanisms underlying the survival of intracellular parasites such as mycobacteria in host macrophages remain poorly understood. In mice, mutations at the Nramp1 gene (for natural resistance-associated macrophage protein), cause susceptibility to mycobacterial infections. Nramp1 encodes an integral membrane protein that is recruited to the phagosome membrane in infected macrophages. In this study, we used microfluorescence ratio imaging of macrophages from wild-type and Nramp1 mutant mice to analyze the effect of loss of Nramp1 function on the properties of phagosomes containing inert particles or live mycobacteria. The pH of phagosomes containing live Mycobacterium bovis was significantly more acidic in Nramp1- expressing macrophages than in mutant cells (pH 5.5 ± 0.06 versus pH 6.6 ± 0.05, respectively; P <0.005). The enhanced acidification could not be accounted for by differences in proton consumption during dismutation of superoxide, phagosomal buffering power, counterion conductance, or in the rate of proton “leak”, as these were found to be comparable in wild-type and Nramp1-deficient macrophages. Rather, after ingestion of live mycobacteria, Nramp1-expressing cells exhibited increased concanamycin-sensitive H+ pumping across the phagosomal membrane. This was associated with an enhanced ability of phagosomes to fuse with vacuolar-type ATPase–containing late endosomes and/or lysosomes. This effect was restricted to live M. bovis and was not seen in phagosomes containing dead M. bovis or latex beads. These data support the notion that Nramp1 affects intracellular mycobacterial replication by modulating phagosomal pH, suggesting that Nramp1 plays a central role in this process.
Expression of Interleukin 9 in the Lungs of  Transgenic Mice Causes Airway Inflammation, Mast Cell Hyperplasia, and Bronchial Hyperresponsiveness
Authors: Temann Ulla-Angela , Geba Gregory P. , Rankin John A. , Flavell Richard A.
Published: July 2002

Interleukin (IL)-9, a pleiotropic cytokine produced by the Th2 subset of T lymphocytes has been proposed as product of a candidate gene responsible for asthma. Its wide range of biological functions on many cell types involved in the allergic immune response suggests a potentially important role in the complex pathogenesis of asthma. To investigate the contributions of IL-9 to airway inflammation and airway hyperresponsiveness in vivo, we created transgenic mice in which expression of the murine IL-9 cDNA was regulated by the rat Clara cell 10 protein promoter. Lung selective expression of IL-9 caused massive airway inflammation with eosinophils and lymphocytes as predominant infiltrating cell types. A striking finding was the presence of increased numbers of mast cells within the airway epithelium of IL-9–expressing mice. Other impressive pathologic changes in the airways were epithelial cell hypertrophy associated with accumulation of mucus-like material within nonciliated cells and increased subepithelial deposition of collagen. Physiologic evaluation of IL-9–expressing mice demonstrated normal baseline airway resistance and markedly increased airway hyperresponsiveness to inhaled methacholine. These findings strongly support an important role for IL-9 in the pathogenesis of asthma.
Contribution of Nitric Oxide Synthases 1, 2, and 3 to Airway Hyperresponsiveness and Inflammation in a Murine Model of Asthma
Authors: De Sanctis George T. , MacLean James A. , Hamada Kaoru , Mehta Sanjay , Scott Jeremy A. , Jiao Aiping , Yandava Chandri N. , Kobzik Lester , Wolyniec Walter W. , Fabian Attila J. , Venugopal Changaram S. , Grasemann Hartmut , Huang Paul L. , Drazen Jeffrey M.
Published: July 2002

Asthma is a chronic disease characterized by increased airway responsiveness and airway inflammation. The functional role of nitric oxide (NO) and the various nitric oxide synthase (NOS) isoforms in human asthma is controversial. To investigate the role of NO in an established model of allergic asthma, mice with targeted deletions of the three known isoforms of NOS (NOS1, 2, and 3) were studied. Although the inducible (NOS2) isoform was significantly upregulated in the lungs of ovalbumin (OVA)-sensitized and -challenged (OVA/OVA) wild-type (WT) mice and was undetectable in similarly treated NOS2-deficient mice, airway responsiveness was not significantly different between these groups. OVA/OVA endothelial (NOS3)-deficient mice were significantly more responsive to methacholine challenge compared with similarly treated NOS1 and NOS1&3-deficient mice. Airway responsiveness in OVA/OVA neuronal (NOS1)-deficient and neuronal/endothelial (NOS1&3) double-deficient mice was significantly less than that observed in similarly treated NOS2 and WT groups. These findings demonstrate an important function for the nNOS isoform in controlling the inducibility of airway hyperresponsiveness in this model of allergic asthma.
Immunoglobulin-binding Sites of Human FcαRI (CD89) and Bovine Fcγ2R Are Located in their Membrane-distal Extracellular Domains
Authors: Craig Morton H. , van Zandbergen Ger , van Kooten Cees , Howard Chris J. , van de Winkel Jan G. J. , Brandtzaeg Per
Published: July 2002

To localize the immunoglobulin (Ig)-binding regions of the human Fcα receptor (FcαRI, CD89) and the bovine Fcγ2 receptor (bFcγ2R), chimeric receptors were generated by exchanging comparable regions between these two proteins. FcαRI and bFcγ2R are highly homologous and are more closely related to each other than to other human and bovine FcRs. Nevertheless, they are functionally distinct in that FcαRI binds human IgA (hIgA) but not bovine IgG2 (bIgG2), whereas bFcγ2R binds bIgG2 but not hIgA. FcαRI and bFcγ2R possess extracellular regions consisting of two Ig-like domains, a membrane-distal extracellular domain (EC1), a membrane-proximal EC domain (EC2), a transmembrane region, and a short cytoplasmic tail. Chimeras constructed by exchanging complete domains between these two receptors were transfected to COS-1 cells and assayed for their ability to bind hIgA- or bIgG2-coated beads. The results showed that the Ig-binding site of both FcαRI and bFcγ2R is located within EC1. Supporting this observation, monoclonal antibodies that blocked IgA binding to FcαRI were found to recognize epitopes located in this domain. In terms of FcR–Ig interactions characterized thus far, this location is unique and surprising because it has been shown previously that leukocyte FcγRs and FcεRI bind Ig via sites principally located in their EC2 domains.
C-reactive Protein: A Physiological Activator of Interleukin 6 Receptor Shedding
Authors: Jones Simon A. , Novick Daniela , Horiuchi Sankichi , Yamamoto Naoki , Szalai Alexander J. , Fuller Gerald M.
Published: July 2002

The soluble interleukin 6 receptor (sIL-6R) circulates at elevated levels in various diseases. This suggests that inflammatory mediators control sIL-6R release. Through examination of human neutrophils, it was found that the acute phase reactant C-reactive protein (CRP) activates a threefold increase in sIL-6R production. Maximal release occurred after 30–60 min exposure to CRP (50 μg/ml), and was mimicked by peptides corresponding to amino acid residues 174– 185 and 201–206 of native CRP. A third peptide fragment (77–82) had no effect. Differential mRNA splicing did not account for the CRP-mediated release of sIL-6R, since this isoform was not detected in conditioned media. Furthermore, stimulation of neutrophils with CRP or with peptides 174–185 or 201–206 promoted a loss of membrane-bound IL-6R, suggesting release by proteolytic shedding. The metalloprotease inhibitor TAPI had only a marginal effect on CRP-mediated sIL-6R release, suggesting that shedding occurs via a mechanism distinct from that previously reported. It well established that IL-6 stimulates the acute phase expression of CRP. Our current findings demonstrate a novel relationship between these two mediators, since CRP may affect IL-6–mediated inflammatory events by enabling formation of the sIL-6R/IL-6 complex.
NKp44, A Triggering Receptor Involved in Tumor Cell Lysis by Activated Human Natural Killer Cells, Is a Novel Member of the Immunoglobulin Superfamily
Authors: Cantoni Claudia , Bottino Cristina , Vitale Massimo , Pessino Anna , Augugliaro Raffaella , Malaspina Angela , Parolini Silvia , Moretta Lorenzo , Moretta Alessandro , Biassoni Roberto
Published: July 2002

Surface receptors involved in natural killer (NK) cell triggering during the process of tumor cell lysis have recently been identified. Of these receptors, NKp44 is selectively expressed by IL-2– activated NK cells and may contribute to the increased efficiency of activated NK cells to mediate tumor cell lysis. Here we describe the molecular cloning of NKp44. Analysis of the cloned cDNA indicated that NKp44 is a novel transmembrane glycoprotein belonging to the Immunoglobulin superfamily characterized by a single extracellular V-type domain. The charged amino acid lysine in the transmembrane region may be involved in the association of NKp44 with the signal transducing molecule killer activating receptor–associated polypeptide (KARAP)/DAP12. These molecules were found to be crucial for the surface expression of NKp44. In agreement with data of NKp44 surface expression, the NKp44 transcripts were strictly confined to activated NK cells and to a minor subset of TCR-γ/δ+ T lymphocytes. Unlike genes coding for other receptors involved in NK cell triggering or inhibition, the NKp44 gene is on human chromosome 6.
Cc Chemokine Receptor (Ccr)3/Eotaxin Is Followed by Ccr4/Monocyte-Derived Chemokine in Mediating Pulmonary T Helper Lymphocyte Type 2 Recruitment after Serial Antigen Challenge in Vivo
Authors: Lloyd Clare M. , Delaney Tracy , Nguyen Trang , Tian Jane , Martinez-A Carlos , Coyle Anthony J. , Gutierrez-Ramos Jose-Carlos
Published: July 2002

Isolated peripheral blood CD4 cells from allergic individuals express CC chemokine receptor (CCR)3 and CCR4 after expansion in vitro. In addition, human T helper type 2 (Th2) cells polarized in vitro selectively express CCR3 and CCR4 at certain stages of activation/differentiation and respond preferentially to the ligands eotaxin and monocyte-derived chemokine (MDC). However, controversy arises when the in vivo significance of this distinct expression is discussed. To address the functional role of CCR3/eotaxin and CCR4/MDC during the in vivo recruitment of Th2 cells, we have transferred effector Th cells into naive mice to induce allergic airway disease. Tracking of these cells after repeated antigen challenge has established that both CCR3/eotaxin and CCR4/MDC axes contribute to the recruitment of Th2 cells to the lung, demonstrating the in vivo relevance of the expression of these receptors on Th2 cells. We have shown that involvement of the CCR3/eotaxin pathway is confined to early stages of the response in vivo, whereas repeated antigen stimulation results in the predominant use of the CCR4/MDC pathway. We propose that effector Th2 cells respond to both CCR3/eotaxin and CCR4/MDC pathways initially, but that a progressive increase in CCR4-positive cells results in the predominance of the CCR4/MDC axis in the long-term recruitment of Th2 cells in vivo.
Tumor Necrosis Factor Receptor–Associated Factor (Traf)2 Represses the T Helper Cell Type 2 Response through Interaction with Nfat-Interacting Protein (Nip45)
Authors: Lieberson Rebecca , Mowen Kerri A. , McBride Kathryn D. , Leautaud Veronica , Zhang Xiankui , Suh Woong-Kyung , Wu Lin , Glimcher Laurie H.
Published: July 2002

Recently we have identified a novel protein NIP45 (nuclear factor of activated T cells [NFAT]-interacting protein) which substantially augments interleukin (IL)-4 gene transcription. The provision of NIP45 together with NFAT and the T helper cell type 2 (Th2)-specific transcription factor c-Maf to cells normally refractory to IL-4 production, such as B cells or Th1 clones, results in substantial IL-4 secretion to levels that approximate those produced by primary Th2 cells. In studies designed to further our understanding of NIP45 activity, we have uncovered a novel facet of IL-4 gene regulation. We present evidence that members of the tumor necrosis factor receptor–associated factor (TRAF) family of proteins, generally known to function as adapter proteins that transduce signals from the tumor necrosis factor receptor superfamily, contribute to the repression of IL-4 gene transcription and that this effect is mediated through their interaction with NIP45.
Vaccination with Heat-killed Leishmania Antigen or Recombinant Leishmanial Protein and CpG Oligodeoxynucleotides Induces Long-Term Memory CD4+and CD8+T Cell Responses and Protection Against Leishmania major Infection
Authors: Rhee Elizabeth G. , Mendez Susana , Shah Javeed A. , Wu Chang-you , Kirman Joanna R. , Turon Tara N. , Davey Dylan F. , Davis Heather , Klinman Dennis M. , Coler Rhea N. , Sacks David L. , Seder Robert A.
Published: July 2002

CpG oligodeoxynucleotides (ODN) have potent effects on innate and adaptive cellular immune responses. In this report, the ability of CpG ODN to confer long-term immunity and protection when used as a vaccine adjuvant with a clinical grade of leishmanial antigen, autoclaved Leishmania major (ALM), or a recombinant leishmanial protein was studied. In two different mouse models of L. major infection, vaccination with ALM plus CpG ODN was able to control infection and markedly reduce lesion development in susceptible BALB/c and resistant C57BL/6 (B6) mice, respectively, up to 12 wk after immunization. Moreover, B6 mice immunized with ALM plus CpG ODNs were still protected against infectious challenge even 6 mo after vaccination. In terms of immune correlates of protection, ALM plus CpG ODN-vaccinated mice displayed L. major–specific T helper cell 1 and CD8+ responses. In addition, complete protection was markedly abrogated in mice depleted of CD8+ T cells at the time of vaccination. Similarly, mice vaccinated with a recombinant leishmanial protein plus CpG ODN also had long-term protection that was dependent on CD8+ T cells in vivo. Together, these data demonstrate that CpG ODN, when used as a vaccine adjuvant with either a recombinant protein or heat-killed leishmanial antigen, can induce long-term protection against an intracellular infection in a CD8-dependent manner.
The Secretion-coupled Endocytosis Correlates with Membrane Tension Changes in RBL 2H3 Cells
Authors: Dai Jianwu , Ting-Beall H. Ping , Sheetz Michael P.
Published: July 2002

Stimulated secretion in endocrine cells and neuronal synapses causes a rise in endocytosis rates to recover the added membrane. The endocytic process involves the mechanical deformation of the membrane to produce an invagination. Studies of osmotic swelling effects on endocytosis indicate that the increased surface tension is tightly correlated to a significant decrease of endocytosis. When rat basophilic leukemia (RBL) cells are stimulated to secrete, there is a dramatic drop in the membrane tension and only small changes in membrane bending stiffness. Neither the shape change that normally accompanies secretion nor the binding of ligand without secretion causes a drop in tension. Further, tension decreases within 6 s, preceding shape change and measurable changes in endocytosis. After secretion stops, tension recovers. On the basis of these results we suggest that the physical parameter of membrane tension is a major regulator of endocytic rate in RBL cells. Low tensions would stimulate endocytosis and high tensions would stall the endocytic machinery.
Regulation of the Epithelial Na+ Channel by Membrane Tension
Authors: Awayda Mouhamed S. , Subramanyam Muthangi
Published: July 2002

The sensitivity of αβγ rat epithelial Na+ channel (rENaC) to osmotically or mechanically induced changes of membrane tension was investigated in the Xenopus oocyte expression system, using both dual electrode voltage clamp and cell-attached patch clamp methodologies. ENaC whole-cell currents were insensitive to mechanical cell swelling caused by direct injection of 90 or 180 nl of 100-mM KCl. Similarly, ENaC whole-cell currents were insensitive to osmotic cell swelling caused by a 33% decrease of bathing solution osmolarity. The lack of an effect of cell swelling on ENaC was independent of the status of the actin cytoskeleton, as ENaC remained insensitive to osmotic and mechanical cell swelling in oocytes pretreated with cytochalasin B for 2–5 h. This apparent insensitivity of ENaC to increased cell volume and changes of membrane tension was also observed at the single channel level in membrane patches subjected to negative or positive pressures of 5 or 10 in. of water. However, and contrary to the lack of an effect of cell swelling, ENaC currents were inhibited by cell shrinking. A 45-min incubation in a 260-mosmol solution (a 25% increase of solution osmolarity) caused a decrease of ENaC currents (at −100 mV) from −3.42 ± 0.34 to −2.02 ± 0.23 μA (n = 6). This decrease of current with cell shrinking was completely blocked by pretreatment of oocytes with cytochalasin B, indicating that these changes of current are not likely related to a direct effect of cell shrinking. We conclude that αβγ rENaC is not directly mechanosensitive when expressed in a system that can produce a channel with identical properties to those found in native epithelia.
Arterial Branching within the Confines of Fractal L-System Formalism
Authors: Zamir M.
Published: July 2002

Parametric Lindenmayer systems (L-systems) are formulated to generate branching tree structures that can incorporate the physiological laws of arterial branching. By construction, the generated trees are de facto fractal structures, and with appropriate choice of parameters, they can be made to exhibit some of the branching patterns of arterial trees, particularly those with a preponderant value of the asymmetry ratio. The question of whether arterial trees in general have these fractal characteristics is examined by comparison of pattern with vasculature from the cardiovascular system. The results suggest that parametric L-systems can be used to produce fractal tree structures but not with the variability in branching parameters observed in arterial trees. These parameters include the asymmetry ratio, the area ratio, branch diameters, and branching angles. The key issue is that the source of variability in these parameters is not known and, hence, it cannot be accurately reproduced in a model. L-systems with a random choice of parameters can be made to mimic some of the observed variability, but the legitimacy of that choice is not clear.
The index number of an 𝑅-space: An extension of a result of M.Takeuchi’s
Authors: Sánchez Cristián
Published: July 2002

M. Takeuchi proved the following nice result: The “two-number” of a symmetric

R
R

-space is equal to the sum of the Betti numbers of the space with coefficients in

Z
2

Z_2

. In the present paper an extension of this result is given for general

R
R

-spaces.
On cohomology algebras of complex subspace arrangements
Authors: Feichtner Eva , Ziegler Günter
Published: July 2002

The integer cohomology algebra of the complement of a complex subspace arrangement with geometric intersection lattice is completely determined by the combinatorial data of the arrangement. We give a combinatorial presentation of the cohomology algebra in the spirit of the Orlik-Solomon result on the cohomology algebras of complex hyperplane arrangements. Our methods are elementary: we work with simplicial models for the complements that are induced by combinatorial stratifications of complex space. We describe simplicial cochains that generate the cohomology. Among them we distinguish a linear basis, study cup product multiplication, and derive an algebra presentation in terms of generators and relations.
A sharp bound for the ratio of the first two Dirichlet eigenvalues of a domain in a hemisphere of 𝕊ⁿ
Authors: Ashbaugh Mark , Benguria Rafael
Published: July 2002

For a domain

Ω
\Omega

contained in a hemisphere of the

n
n

–dimensional sphere

S

n

\mathbb {S}^n

we prove the optimal result

λ
2

/

λ
1

(
Ω
)
≤

λ
2

/

λ
1

(

Ω

⋆

)

\lambda _2/\lambda _1(\Omega ) \le \lambda _2/\lambda _1(\Omega ^{\star })

for the ratio of its first two Dirichlet eigenvalues where

Ω

⋆

\Omega ^{\star }

, the symmetric rearrangement of

Ω
\Omega

in

S

n

\mathbb {S}^n

, is a geodesic ball in

S

n

\mathbb {S}^n

having the same

n
n

–volume as

Ω
\Omega

. We also show that

λ
2

/

λ
1

\lambda _2/\lambda _1

for geodesic balls of geodesic radius

θ
1

\theta _1

less than or equal to

π

/

2

\pi /2

is an increasing function of

θ
1

\theta _1

which runs between the value

(

j

n

/

2
,
1

/

j

n

/

2
−
1
,
1

)
2

(j_{n/2,1}/j_{n/2-1,1})^2

for

θ
1

=
0

\theta _1=0

(this is the Euclidean value) and

2
(
n
+
1
)

/

n

2(n+1)/n

for

θ
1

=
π

/

2

\theta _1=\pi /2

. Here

j

ν
,
k

j_{\nu ,k}

denotes the

k
k

th positive zero of the Bessel function

J

ν

(
t
)

J_{\nu }(t)

. This result generalizes the Payne–Pólya–Weinberger conjecture, which applies to bounded domains in Euclidean space and which we had proved earlier. Our method makes use of symmetric rearrangement of functions and various technical properties of special functions. We also prove that among all domains contained in a hemisphere of

S

n

\mathbb {S}^n

and having a fixed value of

λ
1

\lambda _1

the one with the maximal value of

λ
2

\lambda _2

is the geodesic ball of the appropriate radius. This is a stronger, but slightly less accessible, isoperimetric result than that for

λ
2

/

λ
1

\lambda _2/\lambda _1

. Various other results for

λ
1

\lambda _1

and

λ
2

\lambda _2

of geodesic balls in

S

n

\mathbb {S}^n

are proved in the course of our work.
Widths of Subgroups
Authors: Gitik Rita , Mitra Mahan , Rips Eliyahu , Sageev Michah
Published: July 2002

We say that the width of an infinite subgroup

H
H

in

G
G

is

n
n

if there exists a collection of

n
n

essentially distinct conjugates of

H
H

such that the intersection of any two elements of the collection is infinite and

n
n

is maximal possible. We define the width of a finite subgroup to be

0
0

. We prove that a quasiconvex subgroup of a negatively curved group has finite width. It follows that geometrically finite surfaces in closed hyperbolic

3
3

-manifolds satisfy the

k
k

-plane property for some

k
k

.
Further investigations with the strong probable prime test
Authors: Burthe Ronald
Published: July 2002

Recently, Damgård, Landrock and Pomerance described a procedure in which a

k
k

-bit odd number is chosen at random and subjected to

t
t

random strong probable prime tests. If the chosen number passes all

t
t

tests, then the procedure will return that number; otherwise, another

k
k

-bit odd integer is selected and then tested. The procedure ends when a number that passes all

t
t

tests is found. Let

p

k
,
t

p_{k,t}

denote the probability that such a number is composite. The authors above have shown that

p

k
,
t

≤

4

−
t

p_{k,t}\le 4^{-t}

when

k
≥
51

k\ge 51

and

t
≥
1

t\ge 1

. In this paper we will show that this is in fact valid for all

k
≥
2

k\ge 2

and

t
≥
1

t\ge 1

.
A continuity property of multivariate Lagrange interpolation
Authors: Bloom Thomas , Calvi Jean-Paul
Published: July 2002

Let

{

S

t

}

\{S_{t}\}

be a sequence of interpolation schemes in

R

n

{\mathbb {R}}^{n}

of degree

d
d

(i.e. for each

S

t

S_{t}

one has unique interpolation by a polynomial of total degree

≤
d
)

\leq d)

and total order

≤
l

\leq l

. Suppose that the points of

S

t

S_{t}

tend to

0
∈

R

n

0 \in {\mathbb {R}}^{n}

as

t
→
∞

t \to \infty

and the Lagrange-Hermite interpolants,

H

S

t

H_{S_{t}}

, satisfy

lim

t
→
∞

H

S

t

(

x

α

)
=
0

\lim _{t\to \infty } H_{S_{t}} (x^{\alpha }) = 0

for all monomials

x

α

x^{\alpha }

with

|

α

|

=
d
+
1

|\alpha | = d+1

. Theorem:

lim

t
→
∞

H

S

t

(
f
)
=

T

d

(
f
)

\lim _{t\to \infty } H_{S_{t}} (f) = T^{d} (f)

for all functions

f
f

of class

C

l
−
1

C^{l-1}

in a neighborhood of

0
0

. (Here

T

d

(
f
)

T^{d} (f)

denotes the Taylor series of

f
f

at 0 to order

d
d

.) Specific examples are given to show the optimality of this result.
Classification of integral lattices with large class number
Authors: Scharlau Rudolf , Hemkemeier Boris
Published: July 2002

A detailed exposition of Kneser’s neighbour method for quadratic lattices over totally real number fields, and of the sub-procedures needed for its implementation, is given. Using an actual computer program which automatically generates representatives for all isomorphism classes in one genus of rational lattices, various results about genera ofℓ\ell-elementary lattices, for small prime levelℓ,\ell ,are obtained. For instance, the class number of1212-dimensional77-elementary even lattices of determinant767^6is395395; no extremal lattice in the sense of Quebbemann exists. The implementation incorporates as essential parts previous programs of W. Plesken and B. Souvignier.
Iterative solution of two matrix equations
Authors: Guo Chun-Hua , Lancaster Peter
Published: July 2002

We study iterative methods for finding the maximal Hermitian positive definite solutions of the matrix equationsX+A∗X−1A=QX+A^*X^{-1}A=QandX−A∗X−1A=QX-A^*X^{-1}A=Q, whereQQis Hermitian positive definite. General convergence results are given for the basic fixed point iteration for both equations. Newton’s method and inversion free variants of the basic fixed point iteration are discussed in some detail for the first equation. Numerical results are reported to illustrate the convergence behaviour of various algorithms.