bluuebunny/crossref_metadata_2025 huggingface dataset:
Tumor necrosis factor receptor family member RANK mediates osteoclast differentiation and activation induced by osteoprotegerin ligand
Authors: Hsu Hailing , Lacey David L. , Dunstan Colin R. , Solovyev Irina , Colombero Anne , Timms Emma , Tan Hong-Lin , Elliott Gary , Kelley Michael J. , Sarosi Ildiko , Wang Ling , Xia Xing-Zhong , Elliott Robin , Chiu Laura , Black Tabitha , Scully Sheila , Capparelli Casey , Morony Sean , Shimamoto Grant , Bass Michael B. , Boyle William J.
Published: July 2002

A receptor that mediates osteoprotegerin ligand (OPGL)-induced osteoclast differentiation and activation has been identified via genomic analysis of a primary osteoclast precursor cell cDNA library and is identical to the tumor necrosis factor receptor (TNFR) family member RANK. The RANK mRNA was highly expressed by isolated bone marrow-derived osteoclast progenitors and by mature osteoclasts
in vivo
. Recombinant OPGL binds specifically to RANK expressed by transfected cell lines and purified osteoclast progenitors. Transgenic mice expressing a soluble RANK-Fc fusion protein have severe osteopetrosis because of a reduction in osteoclasts, similar to OPG transgenic mice. Recombinant RANK-Fc binds with high affinity to OPGL
in vitro
and blocks osteoclast differentiation and activation
in vitro
and
in vivo
. Furthermore, polyclonal Ab against the RANK extracellular domain promotes osteoclastogenesis in bone marrow cultures suggesting that RANK activation mediates the effects of OPGL on the osteoclast pathway. These data indicate that OPGL-induced osteoclastogenesis is directly mediated through RANK on osteoclast precursor cells.
Statistical mechanics of protein-like heteropolymers
Authors: Dima Ruxandra I. , Banavar Jayanth R. , Cieplak Marek , Maritan Amos
Published: July 2002

A strategy is outlined for obtaining the free energy of a typical designed heteropolymer. The design procedure considers the probability that the target conformation is occupied in comparison with all the other conformations that could house the given sequence. Numerical calculations on lattice heteropolymer models are presented to illustrate the key physical principles.
A human model for multigenic inheritance: Phenotypic expression in Hirschsprung disease requires both the RET gene and a new 9q31 locus
Authors: Bolk Stacey , Pelet Anna , Hofstra Robert M. W. , Angrist Misha , Salomon Remi , Croaker David , Buys Charles H. C. M. , Lyonnet Stanislas , Chakravarti Aravinda
Published: July 2002

Reduced penetrance in genetic disorders may be either dependent or independent of the genetic background of gene carriers. Hirschsprung disease (HSCR) demonstrates a complex pattern of inheritance with ≈50% of familial cases being heterozygous for mutations in the receptor tyrosine kinase
RET
. Even when identified, the penetrance of
RET
mutations is only 50–70%, gender-dependent, and varies with the extent of aganglionosis. We searched for additional susceptibility genes which, in conjunction with
RET
, lead to phenotypic expression by studying 12 multiplex HSCR families. Haplotype analysis and extensive mutation screening demonstrated three types of families: six families harboring severe
RET
mutations (group I); and the six remaining families, five of which are
RET
-linked families with no sequence alterations and one
RET
-unlinked family (group II). Although the presence of
RET
mutations in group I families is sufficient to explain HSCR inheritance, a genome scan reveals a new susceptibility locus on 9q31 exclusively in group II families. As such, the gene at 9q31 is a modifier of HSCR penetrance. These observations imply that identification of new susceptibility factors in a complex disease may depend on classification of families by mutational type at known susceptibility genes.
Population structure and recent evolution of
Plasmodium falciparum
Authors: Rich Stephen M. , Ayala Francisco J.
Published: July 2002

Plasmodium falciparum
is the agent of malignant
malaria, one of mankind's most severe maladies. The parasite exhibits
antigenic polymorphisms that have been postulated to be ancient. We
have proposed that the extant world populations of
P.
falciparum
have derived from one single parasite, a
cenancestor, within the last 5,000–50,000 years. This inference
derives from the virtual or complete absence of synonymous nucleotide
polymorphisms at genes not involved in immune or drug responses.
Seeking to conciliate this claim with extensive antigenic polymorphism,
we first note that allele substitutions or polymorphisms can arise very
rapidly, even in a single generation, in large populations subject to
strong natural selection. Second, new alleles can arise not only by
single-nucleotide mutations, but also by duplication/deletion of
short simple-repeat DNA sequences, a process several orders of
magnitude faster than single-nucleotide mutation. We analyze three
antigenic genes known to be extremely polymorphic:
Csp,
Msp-1
, and
Msp-2
. We identify regions consisting
of tandem or proximally repetitive short DNA sequences, including some
previously unnoticed. We conclude that the antigenic polymorphisms are
consistent with the recent origin of the world populations of
P.
falciparum
inferred from the analysis of nonantigenic genes.
The paradox of alloreactivity and self MHC restriction: Quantitative analysis and statistics
Authors: Detours Vincent , Perelson Alan S.
Published: July 2002

Although 1–24% of T cells are alloreactive, i.e., respond to MHC molecules encoded by a foreign haplotype, it is generally believed that T cells cannot recognize foreign peptides binding foreign MHC molecules. We show using a quantitative model that, if T cell selection and activation are affinity-driven, then an alloreactivity of 1–24% is incompatible with the textbook notion that self MHC restriction is absolute. If an average of 1% of clones are alloreactive, then according to our model, at most 20-fold more clones should, on average, be activated by antigens presented on self MHC than by antigens presented on foreign MHC. This ratio is at best 5 if alloreactivity is 5%. These results describe average properties of the murine immune system, but not the outcome of individual experiments. Using supercomputer technology, we simulated 100,000 MHC restriction experiments. Although the average restriction ratio was 7.1, restriction was absolute in 10% of the simulated experiments, greater than 100, although not absolute, in 29%, and below 6 in 24%. This extreme variability agrees with experimental estimates. Our analysis suggests that alloreactivity and average self MHC restriction both cannot be high, but that a low average restriction level is compatible with high levels in a significant number of experiments.
CBP/p300 interact with and function as transcriptional coactivators of BRCA1
Authors: Pao Gerald M. , Janknecht Ralf , Ruffner Heinz , Hunter Tony , Verma Inder M.
Published: July 2002

BRCA1 is a breast and ovarian cancer-specific tumor suppressor, with properties of a transcription factor involved in DNA repair. We previously have shown the transactivation of heterologous promoters by the carboxyl terminus of BRCA1. We now describe that BRCA1-mediated transactivation is enhanced by p300/CBP (CREB binding protein) and that this effect was suppressed by the adenovirus E1A oncoprotein. We show a physical association of BRCA1 with the transcriptional coactivators/acetyltransferases p300 and CBP. Endogenous as well as overexpressed BRCA1 and p300 were found to associate in a phosphorylation-independent manner. BRCA1 interacts with the cAMP response element binding protein (CREB) domain of p300/CBP via both its amino and carboxyl termini. Finally, full-length BRCA1 is shown to transcriptionally activate the Rous sarcoma virus-long terminal repeat promoter, which was further stimulated by p300. Immunocolocalization analyses suggest that BRCA1 and p300 associate in a cell cycle-dependent manner. Our results support a role for BRCA1 in transcription.
The dual functions of Fas ligand in the regulation of peripheral CD8+and CD4+T cells
Authors: Suzuki Ivy , Fink Pamela J.
Published: July 2002

Although Fas ligand (FasL) is well characterized for its capacity to deliver a death signal through its receptor Fas, recent work demonstrates that FasL also can receive signals facilitating antigen (Ag)-specific proliferation of CD8+T cells. The fact that thegldmutation differentially influences the proliferative capacity of CD8+and CD4+T cells presented the intriguing possibility that a single molecule may play opposing roles in these two subpopulations. The present study focuses on how these positive and negative regulatory roles are balanced. We show that naive CD4+T cells are responsive to FasL-mediated costimulation on encounter with Ag when Fas-mediated death is prevented. Thus, the machinery responsible for transducing the FasL positive reverse signal operates in both CD4+and CD8+T cells. Instead, differential control of FasL expression distinguishes the role of FasL in these two T cell subpopulations. FasL costimulation occurs immediately on T cell receptor ligation and correlates with the up-regulation of FasL expression on CD8+and naive CD4+T cells, both of which are sensitive to the FasL costimulatory signal. Conversely, FasL-initiated death occurs late in an immune response when high levels of FasL expression are maintained on CD4+T cells that are sensitive to Fas-mediated death, but not on CD8+T cells that are relatively insensitive to this signal. This careful orchestration of FasL expression during times of susceptibility to costimulation and conversely, to death, endows FasL with the capacity to both positively and negatively regulate the peripheral T cell compartment.
A recombination hotspot delimits a wild-species quantitative trait locus for tomato sugar content to 484 bp within an invertase gene
Authors: Fridman Eyal , Pleban Tzili , Zamir Dani
Published: July 2002

In nature, genetic variation usually takes the form of a continuous phenotypic range rather than discrete classes. The genetic variation underlying quantitative traits results from the segregation of numerous interacting quantitative trait loci (QTLs), whose expression is modified by the environment. To uncover the molecular basis of this variation, we characterized a QTL (Brix9-2-5) derived from the green-fruited tomato speciesLycopersicon pennellii. The wild-species allele increased glucose and fructose contents in cultivated tomato fruits in various genetic backgrounds and environments. Using nearly isogenic lines for the QTL, high-resolution mapping analysis delimitedBrix9-2-5to a single nucleotide polymorphism-defined recombination hotspot of 484 bp spanning an exon and intron of a fruit-specific apoplastic invertase. We suggest that the differences between theBrix9-2-5alleles of the two species are associated with a polymorphic intronic element that modulates sink strength of tomato fruits. Our results demonstrate a link between naturally occurring DNA variation and a Mendelian determinant of a complex phenotype for a yield-associated trait.
Dialectical dialogue: the struggle for speech, repressive silence, and the shift to multiplicity
Authors: Gurevitch Zali
Published: July 2002

In the present essay I intend to explore ‘dialectical dialogue’ in three distinct moments: the battle for recognition, the ethics of giving recognition, and the multiplicity of conversation. The essay begins with Hegel's figures of Master and Slave portraying the struggle of speech for recognition. This struggle culminates in a duel for mastery, which implies the repression and silencing of the other's speech. Ethical dialogue comes as a response to repressive silence, calling the other into egalitarian exchange. Ethical dialogue as such, however, remains within the dialectical framework of agonistic relations. To shift from dialectics to multiplicity, the essay turns from the politics of recognition to the poetics of conversation, to polyphony and to passage. I will follow the three moments both separately, through particular dialogic instances and theoretical perspectives, and as they develop, respond to, and shift from one to the other. Together they will portray an idea of the ‘social’ as a critical dialogic stance with its inherent dialectical betweenness and potential opening and expanding multiplicity.
Analysing patterns of religious participation in post‐communist Eastern Europe1
Authors: Need Ariana , Evans Geoffrey
Published: July 2002

It is generally thought that processes of modernization generic to industrialized societies have resulted in a process of secularization with respect to conventional religious participation and observance in most Western countries. It is not at all clear, however, whether the post‐communist societies of Eastern Europe have followed this pattern. In this we paper we examine whether levels of religiosity in ten post‐communist societies – five generally Catholic in orientation and five Orthodox – are consistent with secularization theory, or whether instead they display, as some have suggested, the impact of seven decades of atheistic communism followed by a recent resurgence among the young. For this purpose we examine denominational membership and church attendance using descriptive and multivariate analysis of large‐scale national sample surveys conducted in the mid‐1990s. We find that age and educational differences in participation rates follow patterns expected on the basis of secularization theory with no evidence of resurgence among younger groups. Also, however, Catholic participation rates are significantly higher than Orthodox ones, indicating the importance of denomination in understanding patterns of religiosity in the post‐communist context.
Abstract and engaged critique in sociology: on football hooliganism
Authors: King Anthony
Published: July 2002

This note is a response to a critical review of some of my own work published recently in the British Journal of Sociology but it does not reply to the specific criticisms made in that article. Rather it addresses the question of what constitutes appropriate critique in sociology by developing a distinction between abstract and engaged criticism.
Redintegration and Response Suppression in Serial Recall: A Dynamic Network Model
Authors: Lewandowsky Stephan
Published: July 2002

This article presents a dynamic network model of redintegration and response suppression. Redintegration is the process that disambiguates partially retrieved memorial information into an overt response, and response suppression renders retrieved items temporarily unavailable for further report. Most models of serial recall assume the presence of both processes, but few explain how they are performed. Exploration of the network revealed that it can predict recency in serial recall of lists of varying lengths, the pattern of the associated transposition, omission, intrusion, and repetition errors, and the temporal dynamics of retrieval. The network thus augments any existing model of serial recall that assumes a distributed vector representation but does not specify the processes underlying redintegration and response suppression.
The Impact of Public Transport on US Metropolitan Wage Inequality
Authors: Sanchez Thomas W.
Published: July 2002

This article presents a wage inequality analysis for 158 large US metropolitan statistical areas (MSAs). The analysis is concerned with whether public transport has a detectable influence on 1990 levels of wage equality. Because public transport systems are generally designed to link residences with employment locations, higher levels of service provision, all other factors being equal, should be associated with higher employment rates and more uniform distributions of earnings. Few analyses, however, have attempted to evaluate public policies that affect wage distributions. The results of this research provide a macroscopic view of the effectiveness of urban transport investments with respect to urban wage inequality.
Anatomy of a New Ethnic Settlement: The Chinese Ethnoburb in Los Angeles
Authors: Li Wei
Published: July 2002

This paper proposes a new model of ethnic settlement, the ethnoburb. Ethnoburbs are suburban ethnic clusters of residential areas and business districts in large American metropolitan areas. They are multi-ethnic communities, in which one ethnic minority group has a significant concentration, but does not necessarily comprise a majority. The paper operationalises the ethnoburb model via an analysis of the demographic profiles and socioeconomic characteristics of the ethnoburban Chinese population in Los Angeles in order to understand the ethnoburb's role as a global economic outpost. This analysis also highlights social stratification by country of origin, and the micro-geographies of neighbourhood and workplace, features which reveal the ethnoburb's character as an urban mosaic.
Judging and coding facial expression of emotions in congenitally blind children
Authors: Galati Dario , Miceli Renato , Sini Barbara
Published: July 2002

We investigate the facial expression of emotions in very young congenitally blind children to ” nd out whether these are objectively and subjectively recognisable. We also try to see whether the adequacy of the facial expression of emotions changes as the children get older. We video recorded the facial expressions of 10 congenitally blind children and 10 sighted children (as a control group) in seven everyday situations considered as emotion elicitors. The recorded sequences were analysed according to the Maximally Discriminative Facial Movement Coding System (Max; Izard, 1979) and then judged by 280 decoders who used four scales (two dimensional and two categorical) for their answers. The results showed that all the subjects (both the blind and the sighted) were able to express their emotions facially, though not always according to the theoretically expected pattern. Recognition of the various expressions was fairly accurate, but some emotions were systematically confused with others. The decoders’ answers to the dimensional and categorical scales were similar for both blind and sighted subjects. Our ” ndings on objective and subjective judgements show that there was no decrease in the facial expressiveness of the blind children in the period of development considered.
Adolescent perceptions of reciprocity, authority, and closeness in relationships with mothers, fathers, and friends
Authors: Laursen Brett , Noack Peter , Wilder David , Williams Vickie
Published: July 2002

Adolescents in Germany and the United States completed questionnaires describing reciprocity, authority, and closeness in relationships with mothers, fathers, and friends. Reciprocity was linked to authority within and across friendships and parent-child relationships; reciprocity and authority were linked to closeness within and across parent-child relationships, but neither within friendships nor across friendships and parent-child relationships. Median splits divided adolescents into high and low closeness groups for each relationship to determine differences in reciprocity and authority. Patterns of reciprocity varied as a function of relationship closeness and nationality, as well as by age and gender. Patterns of authority differed by nationality only.
Preventing and curtailing injecting drug use: a review of opportunities for developing and delivering ‘route transition interventions’
Authors: HUNT NEIL , GRIFFITHS PAUL , SOUTHWELL MATHEW , STILLWELL GARRY , STRANG JOHN
Published: July 2002

Injecting is an important cause of viral and bacterial infection among drug users and is also associated with increased risk of overdose and severe dependence. Even when aggregate numbers of illicit drug users remain constant, significant health and social benefits may be achieved by a reduction in the prevalence and/or frequency of injecting. Yet, to date, little attention has been paid to reducing injecting (rather than drug use) as a policy objective. This paper reviews a range of ‘route transition interventions' (RTIs) that can be used to reduce injecting and its associated harms. Two points for intervention are distinguished: preventing injecting among existing non‐injecting drug users and promoting the transition away from injecting among current injectors. Targets for basic research and programme evaluation are discussed. In particular, it is argued that the time is now right for regional or national case studies that investigate how injecting can be reduced. [Hunt N, Griffiths P, Southwell M, Stillwell G, Strang J. Preventing and curtailing injecting drug use: a review of opportunities for developing and delivering route transition interventions’. Drug Alcohol Rev 1999;18:441–451]
Statisticians and the History of Economics
Authors: Stigler Stephen
Published: July 2002

Over twenty years ago, I had the pleasure of speaking to the Royal Statistical Society about the life and work in statistics of Francis Ysidro Edgeworth. In a preamble to that talk, I commented upon some similarities between Edgeworth and an even earlier scientist, Daniel Bernoulli, who lived from 1700 to 1782. One similarity I mentioned would be so well-known to this audience that it scarcely bears repetition: Both Edgeworth and Bernoulli were important in the histories of both economics and statistics. Of Edgeworth's work in economics I need not comment—I expect that his work on taxation, price theory, international trade, and index numbers is familiar to many in this audience. Edgeworth's work in statistics was no less important in at least four ways: (1) He was an astute and original philosopher of the application of probability and quantitative thinking in social science; (2) he had sufficient mathematical genius to situate Galton's concept of correlation in the framework of the multivariate normal distribution, thereby pointing the way for Karl Pearson to develop correlational analysis—Edgeworth even has a claim on being the inventor of the product moment correlation coefficient; (3) he pioneered the exploration of many topics, such as variance component estimation, the theory of maximum likelihood, and series expansions for sampling distributions; and (4) he had an amazing ability to explore the limits of statistical concepts by constructing subtle and surprising counterexamples to widely accepted truths.
Update on Anticonvulsants for the Treatment of Alcohol Withdrawal
Authors: Malcolm Robert , Myrick Hugh , Brady Kathleen T. , Ballenger James C.
Published: July 2002

Some anticonvulsants have been shown to be as effective as some benzodiazepines for the treatment of alcohol withdrawal. Anticonvulsants may offer advantages over benzodiazepines in the outpatient treatment of alcohol withdrawal: they lack abuse potential, have minimal interactions with alcohol, and may be more effective in ameliorating psychiatric symptoms of alcohol withdrawal. Carbamazepine appears to be as effective as lorazepam and oxazepam in ameliorating the symptoms of alcohol withdrawal. In addition, a recent study indicates that carbamazepine may suppress post‐withdrawal alcohol use. Divalproex may also reduce symptoms of alcohol withdrawal, based on several open‐label studies. However, both carbamazepine and divalproex have limited usefulness in alcoholics with severe hepatic or hematologic complications. Newer anticonvulsants, such as gabapentin and vigabatrin, also appear to reduce alcohol withdrawal symptoms in preclinical and open‐label clinical trials while lacking the toxicities of carbamazepine and divalproex. Controlled trials are underway exploring the efficacy and safety of newer anticonvulsants for the treatment of alcohol withdrawal.
The Links Between Alcohol, Crime and the Criminal Justice System: Explanations, Evidence and Interventions
Authors: Martin Susan E.
Published: July 2002

Many studies indicate that alcohol abuse and dependence are closely linked with the criminal justice system (CJS). Alcohol was consumed prior to about half of all homicides and assaults, and nearly 40 percent of state prisoners report committing their current offense under the influence of alcohol. Alcohol abuse cost approximately $13 billion in 1992 non‐health related costs. This article seeks to address this burden on the CJS and society. It presents a conceptual framework for explaining the alcohol‐crime nexus, reviews empirical evidence of the complex associations between alcohol consumption and crime, and links these with promising intervention strategies to reduce alcohol‐related crime.
Hepatitis B and C in alcohol‐dependent patients admitted to a UK alcohol inpatient treatment unit
Authors: Martínez‐Raga José , Marshall E. Jane , Keaney Francis , Best David , Ball David , Strang John
Published: July 2002

The prevalence of hepatitis B and C infection was studied in a sample of alcohol‐dependent patients admitted to a specialist alcohol inpatient unit to identify factors associated with hepatitis B and C infection. Laboratory, clinical and socio‐demographic data were collected from 277 admissions over a 3‐year period who were tested routinely for markers of hepatitis B and C infection. Of the 275 subjects tested for hepatitis C, 27 (9.8%) were positive to the hepatitis anti‐HCV IgG antibody. Of the 275 subjects tested for hepatitis B, 30 (10.9%) were positive to the hepatitis anti‐HBc IgG antibody. Few differences were found between hepatitis B positive and negative subjects. Hepatitis C positive individuals were more likely than Hepatitis C negative patients to have also been infected with the hepatitis B virus (p < 0.001), to have an unplanned discharge (p < 0.005) and to have ever used cannabis (p < 0.005), cocaine (p < 0.001), amphetamines (p < 0.001) or heroin (p < 0.001). They were also more likely to have a co‐morbid antisocial personality disorder (p < 0.001), a lifetime diagnosis of opiate dependence (p < 0.001) and cocaine dependence (p < 0.005), higher serum gamma glutamyl transferase (GGT) levels (p < 0.05) and a lower platelet count (p < 0.05). These findings may help clinicians to identify those alcohol dependent patients with risk factors for hepatitis virus infection.
The Laminin α Chains: Expression, Developmental Transitions, and Chromosomal Locations of α1-5, Identification of Heterotrimeric Laminins 8–11, and Cloning of a Novel α3 Isoform
Authors: Miner Jeffrey H. , Patton Bruce L. , Lentz Stephen I. , Gilbert Debra J. , Snider William D. , Jenkins Nancy A. , Copeland Neal G. , Sanes Joshua R.
Published: July 2002

Laminin trimers composed of α, β, and γ chains are major components of basal laminae (BLs) throughout the body. To date, three α chains (α1–3) have been shown to assemble into at least seven heterotrimers (called laminins 1–7). Genes encoding two additional α chains (α4 and α5) have been cloned, but little is known about their expression, and their protein products have not been identified. Here we generated antisera to recombinant α4 and α5 and used them to identify authentic proteins in tissue extracts. Immunoprecipitation and immunoblotting showed that α4 and α5 assemble into four novel laminin heterotrimers (laminins 8–11: α4β1γ1, α4β2γ1, α5β1γ1, and α5β2γ1, respectively). Using a panel of nucleotide and antibody probes, we surveyed the expression of α1-5 in murine tissues. All five chains were expressed in both embryos and adults, but each was distributed in a distinct pattern at both RNA and protein levels. Overall, α4 and α5 exhibited the broadest patterns of expression, while expression of α1 was the most restricted. Immunohistochemical analysis of kidney, lung, and heart showed that the α chains were confined to extracellular matrix and, with few exceptions, to BLs. All developing and adult BLs examined contained at least one α chain, all α chains were present in multiple BLs, and some BLs contained two or three α chains. Detailed analysis of developing kidney revealed that some individual BLs, including those of the tubule and glomerulus, changed in laminin chain composition as they matured, expressing up to three different α chains and two different β chains in an elaborate and dynamic progression. Interspecific backcross mapping of the five α chain genes revealed that they are distributed on four mouse chromosomes. Finally, we identified a novel full-length α3 isoform encoded by the Lama3 gene, which was previously believed to encode only truncated chains. Together, these results reveal remarkable diversity in BL composition and complexity in BL development.
Novel β-Secretase Cleavage of β-Amyloid Precursor Protein in the Endoplasmic Reticulum/Intermediate Compartment of NT2N Cells
Authors: Chyung Abraham S.C. , Greenberg Barry D. , Cook David G. , Doms Robert W. , Lee Virginia M.-Y.
Published: July 2002

Previous studies have demonstrated that NT2N neurons derived from a human embryonal carcinoma cell line (NT2) constitutively process the endogenous wild-type β-amyloid precursor protein (APP) to amyloid β peptide in an intracellular compartment. These studies indicate that other proteolytic fragments generated by intracellular processing must also be present in these cells. Here we show that the NH2-terminal fragment of APP generated by β-secretase cleavage (APPβ) is indeed produced from the endogenous full length APP (APPFL). Pulse–chase studies demonstrated a precursor–product relationship between APPFL and APPβ as well as intracellular and secreted APPβ fragments. In addition, trypsin digestion of intact NT2N cells at 4°C did not abolish APPβ recovered from the cell lysates. Furthermore, the production of intracellular APPβ from wild-type APP appears to be a unique characteristic of postmitotic neurons, since intracellular APPβ was not detected in several non-neuronal cell lines. Significantly, production of APPβ occurred even when APP was retained in the ER/ intermediate compartment by inhibition with brefeldin A, incubation at 15°C, or by expression of exogenous APP bearing the dilysine ER retrieval motif.
Moesin Interacts with the Cytoplasmic Region of Intercellular Adhesion Molecule-3 and Is Redistributed to the Uropod of T Lymphocytes during Cell Polarization
Authors: Serrador Juan M. , Alonso-Lebrero José L. , Pozo Miguel A. del , Furthmayr Heinz , Schwartz-Albiez Reinhard , Calvo Javier , Lozano Francisco , Sánchez-Madrid Francisco
Published: July 2002

During activation, T lymphocytes become motile cells, switching from a spherical to a polarized shape. Chemokines and other chemotactic cytokines induce lymphocyte polarization with the formation of a uropod in the rear pole, where the adhesion receptors intercellular adhesion molecule-1 (ICAM-1), ICAM-3, and CD44 redistribute. We have investigated membrane–cytoskeleton interactions that play a key role in the redistribution of adhesion receptors to the uropod. Immunofluorescence analysis showed that the ERM proteins radixin and moesin localized to the uropod of human T lymphoblasts treated with the chemokine RANTES (regulated on activation, normal T cell expressed, and secreted), a polarization-inducing agent; radixin colocalized with arrays of myosin II at the neck of the uropods, whereas moesin decorated the most distal part of the uropod and colocalized with ICAM-1, ICAM-3, and CD44 molecules. Two other cytoskeletal proteins, β-actin and α-tubulin, clustered at the cell leading edge and uropod, respectively, of polarized lymphocytes. Biochemical analysis showed that moesin coimmunoprecipitates with ICAM-3 in T lymphoblasts stimulated with either RANTES or the polarization- inducing anti–ICAM-3 HP2/19 mAb, as well as in the constitutively polarized T cell line HSB-2. In addition, moesin is associated with CD44, but not with ICAM-1, in polarized T lymphocytes. A correlation between the degree of moesin–ICAM-3 interaction and cell polarization was found as determined by immunofluorescence and immunoprecipitation analysis done in parallel. The moesin–ICAM-3 interaction was specifically mediated by the cytoplasmic domain of ICAM-3 as revealed by precipitation of moesin with a GST fusion protein containing the ICAM-3 cytoplasmic tail from metabolically labeled Jurkat T cell lysates. The interaction of moesin with ICAM-3 was greatly diminished when RANTES-stimulated T lymphoblasts were pretreated with the myosin-disrupting drug butanedione monoxime, which prevents lymphocyte polarization. Altogether, these data indicate that moesin interacts with ICAM-3 and CD44 adhesion molecules in uropods of polarized T cells; these data also suggest that these interactions participate in the formation of links between membrane receptors and the cytoskeleton, thereby regulating morphological changes during cell locomotion.
Key Role of the Cdx2 Homeobox Gene in Extracellular Matrix–mediated Intestinal Cell Differentiation
Authors: Lorentz Olivier , Duluc Isabelle , Arcangelis Adèle De , Simon-Assmann Patricia , Kedinger Michèle , Freund Jean-Noël
Published: July 2002

To explore the role of homeobox genes in the intestine, the human colon adenocarcinoma cell line Caco2-TC7 has been stably transfected with plasmids synthesizing Cdx1 and Cdx2 sense and antisense RNAs. Cdx1 overexpression or inhibition by antisense RNA does not markedly modify the cell differentiation markers analyzed in this study. In contrast, Cdx2 overexpression stimulates two typical markers of enterocytic differentiation: sucrase-isomaltase and lactase. Cells in which the endogenous expression of Cdx2 is reduced by antisense RNA attach poorly to the substratum. Conversely, Cdx2 overexpression modifies the expression of molecules involved in cell–cell and cell–substratum interactions and in transduction process: indeed, E-cadherin, integrin-β4 subunit, laminin-γ2 chain, hemidesmosomal protein, APC, and α-actinin are upregulated. Interestingly, most of these molecules are preferentially expressed in vivo in the differentiated villi enterocytes rather than in crypt cells. Cdx2 overexpression also results in the stimulation of HoxA-9 mRNA expression, an homeobox gene selectively expressed in the colon. In contrast, Cdx2-overexpressing cells display a decline of Cdx1 mRNA, which is mostly found in vivo in crypt cells. When implanted in nude mice, Cdx2-overexpressing cells produce larger tumors than control cells, and form glandular and villus-like structures.

Laminin-1 is known to stimulate intestinal cell differentiation in vitro. In the present study, we demonstrate that the differentiating effect of laminin-1 coatings on Caco2-TC7 cells is accompanied by an upregulation of Cdx2. To further document this observation, we analyzed a series of Caco2 clones in which the production of laminin-α1 chain is differentially inhibited by antisense RNA. We found a positive correlation between the level of Cdx2 expression, that of endogenous laminin-α1 chain mRNA and that of sucrase-isomaltase expression in these cell lines.

Taken together, these results suggest (a) that Cdx1 and Cdx2 homeobox genes play distinct roles in the intestinal epithelium, (b) that Cdx2 provokes pleiotropic effects triggering cells towards the phenotype of differentiated villus enterocytes, and (c) that Cdx2 expression is modulated by basement membrane components. Hence, we conclude that Cdx2 plays a key role in the extracellular matrix–mediated intestinal cell differentiation.
A Critical Temporal Requirement for the Retinoblastoma Protein Family During Neuronal Determination
Authors: Slack Ruth S. , El-Bizri Hiba , Wong Josée , Belliveau Daniel J. , Miller Freda D.
Published: July 2002

In this report, we have examined the requirement for the retinoblastoma (Rb) gene family in neuronal determination with a focus on the developing neocortex. To determine whether pRb is required for neuronal determination in vivo, we crossed the Rb−/− mice with transgenic mice expressing β-galactosidase from the early, panneuronal Tα1 α-tubulin promoter (Tα1:nlacZ). In E12.5 Rb−/− embryos, the Tα1:nlacZ transgene was robustly expressed throughout the developing nervous system. However, by E14.5, there were perturbations in Tα1:nlacZ expression throughout the nervous system, including deficits in the forebrain and retina. To more precisely define the temporal requirement for pRb in neuronal determination, we functionally ablated the pRb family in wild-type cortical progenitor cells that undergo the transition to postmitotic neurons in vitro by expression of a mutant adenovirus E1A protein. These studies revealed that induction of Tα1:nlacZ did not require proteins of the pRb family. However, in their absence, determined, Tα1:nlacZ-positive cortical neurons underwent apoptosis, presumably as a consequence of “mixed signals” deriving from their inability to undergo terminal mitosis. In contrast, when the pRb family was ablated in postmitotic cortical neurons, there was no effect on neuronal survival, nor did it cause the postmitotic neurons to reenter the cell cycle. Together, these studies define a critical temporal window of requirement for the pRb family; these proteins are not required for induction of neuronal gene expression or for the maintenance of postmitotic neurons, but are essential for determined neurons to exit the cell cycle and survive.
Overexpression of a Neural-specific Rho Family GTPase, cRac1B, Selectively Induces Enhanced Neuritogenesis and Neurite Branching in Primary Neurons
Authors: Albertinazzi Chiara , Gilardelli Daniela , Paris Simona , Longhi Renato , de Curtis Ivan
Published: July 2002

Rho family GTPases have been implicated in cytoskeletal reorganization during neuritogenesis. We have recently identified a new gene of this family, cRac1B, specifically expressed in the chicken developing nervous system. This GTPase was overexpressed in primary neurons to study the role of cRac1B in the development of the neuronal phenotype. Overexpression of cRac1B induced an increment in the number of neurites per neuron, and dramatically increased neurite branching, whereas overexpression of the highly related and ubiquitous cRac1A GTPase did not evidently affect neuronal morphology. Furthermore, expression of an inactive form of cRac1B strikingly inhibited neurite formation. The specificity of cRac1B action observed in neurons was not observed in fibroblasts, where both GTPases produced similar effects on cell morphology and actin organization, indicating the existence of a cell type-dependent specificity of cRac1B function. Molecular dissection of cRac1B function by analysis of the effects of chimeric cRac1A/cRac1B proteins showed that the COOH-terminal portion of cRac1B is essential to induce increased neuritogenesis and neurite branching. Considering the distinctive regulation of cRac1B expression during neural development, our data strongly support an important role of cRac1B during neuritogenesis, and they uncover new mechanisms underlying the functional specificity of distinct Rho family GTPases.
Processing of the psbA 5′ Untranslated Region in Chlamydomonas reinhardtii Depends upon Factors Mediating Ribosome Association
Authors: Bruick Richard K. , Mayfield Stephen P.
Published: July 2002

The 5′ untranslated region of the chloroplast psbA mRNA, encoding the D1 protein, is processed in Chlamydomonas reinhardtii. Processing occurs just upstream of a consensus Shine-Dalgarno sequence and results in the removal of 54 nucleotides from the 5′ terminus, including a stem-loop element identified previously as an important structure for D1 expression. Examination of this processing event in C. reinhardtii strains containing mutations within the chloroplast or nuclear genomes that block psbA translation reveals a correlation between processing and ribosome association. Mutations within the 5′ untranslated region of the psbA mRNA that disrupt the Shine-Dalgarno sequence, acting as a ribosome binding site, preclude translation and prevent mRNA processing. Similarly, nuclear mutations that specifically affect synthesis of the D1 protein specifically affect processing of the psbA mRNA. In vitro, loss of the stem-loop element does not prohibit the binding of a message-specific protein complex required for translational activation of psbA upon illumination. These results are consistent with a hierarchical maturation pathway for chloroplast messages, mediated by nuclear-encoded factors, that integrates mRNA processing, message stability, ribosome association, and translation.
Kakapo, a Novel Cytoskeletal-associated Protein Is Essential for the Restricted Localization of the Neuregulin-like Factor, Vein, at the Muscle–Tendon Junction Site
Authors: Strumpf Dan , Volk Talila
Published: July 2002

In the Drosophila embryo, the correct association of muscles with their specific tendon cells is achieved through reciprocal interactions between these two distinct cell types. Tendon cell differentiation is initiated by activation of the EGF-receptor signaling pathway within these cells by Vein, a neuregulin-like factor secreted by the approaching myotube. Here, we describe the cloning and the molecular and genetic analyses of kakapo, a Drosophila gene, expressed in the tendons, that is essential for muscle-dependent tendon cell differentiation. Kakapo is a large intracellular protein and contains structural domains also found in cytoskeletal-related vertebrate proteins (including plakin, dystrophin, and Gas2 family members). kakapo mutant embryos exhibit abnormal muscle-dependent tendon cell differentiation. A major defect in the kakapo mutant tendon cells is the failure of Vein to be localized at the muscle–tendon junctional site; instead, Vein is dispersed and its levels are reduced. This may lead to aberrant differentiation of tendon cells and consequently to the kakapo mutant deranged somatic muscle phenotype.
Laminin Polymerization Induces a Receptor–Cytoskeleton Network
Authors: Colognato Holly , Winkelmann Donald A. , Yurchenco Peter D.
Published: July 2002

The transition of laminin from a monomeric to a polymerized state is thought to be a crucial step in the development of basement membranes and in the case of skeletal muscle, mutations in laminin can result in severe muscular dystrophies with basement membrane defects. We have evaluated laminin polymer and receptor interactions to determine the requirements for laminin assembly on a cell surface and investigated what cellular responses might be mediated by this transition. We found that on muscle cell surfaces, laminins preferentially polymerize while bound to receptors that included dystroglycan and α7β1 integrin. These receptor interactions are mediated through laminin COOH-terminal domains that are spatially and functionally distinct from NH2-terminal polymer binding sites. This receptor-facilitated self-assembly drives rearrangement of laminin into a cell-associated polygonal network, a process that also requires actin reorganization and tyrosine phosphorylation. As a result, dystroglycan and integrin redistribute into a reciprocal network as do cortical cytoskeleton components vinculin and dystrophin. Cytoskeletal and receptor reorganization is dependent on laminin polymerization and fails in response to receptor occupancy alone (nonpolymerizing laminin). Preferential polymerization of laminin on cell surfaces, and the resulting induction of cortical architecture, is a cooperative process requiring laminin– receptor ligation, receptor-facilitated self-assembly, actin reorganization, and signaling events.
Dissecting the Translocase and Integrase Functions of the Escherichia coli Secyeg Translocon
Authors: Koch Hans-Georg , Müller Matthias
Published: July 2002

Recent evidence suggests that in Escherichia coli, SecA/SecB and signal recognition particle (SRP) are constituents of two different pathways targeting secretory and inner membrane proteins to the SecYEG translocon of the plasma membrane. We now show that a secY mutation, which compromises a functional SecY–SecA interaction, does not impair the SRP-mediated integration of polytopic inner membrane proteins. Furthermore, under conditions in which the translocation of secretory proteins is strictly dependent on SecG for assisting SecA, the absence of SecG still allows polytopic membrane proteins to integrate at the wild-type level. These results indicate that SRP-dependent integration and SecA/SecB-mediated translocation do not only represent two independent protein delivery systems, but also remain mechanistically distinct processes even at the level of the membrane where they engage different domains of SecY and different components of the translocon. In addition, the experimental setup used here enabled us to demonstrate that SRP-dependent integration of a multispanning protein into membrane vesicles leads to a biologically active enzyme.
Cross-Talk between Two Cysteine Protease Families
Authors: Nakagawa Toshiyuki , Yuan Junying
Published: July 2002

Calpains and caspases are two cysteine protease families that play important roles in regulating pathological cell death. Here, we report that m-calpain may be responsible for cleaving procaspase-12, a caspase localized in the ER, to generate active caspase-12. In addition, calpain may be responsible for cleaving the loop region in Bcl-xL and, therefore, turning an antiapoptotic molecule into a proapoptotic molecule. We propose that disturbance to intracellular calcium storage as a result of ischemic injury or amyloid β peptide cytotoxicity may induce apoptosis through calpain- mediated caspase-12 activation and Bcl-xL inactivation. These data suggest a novel apoptotic pathway involving calcium-mediated calpain activation and cross-talks between calpain and caspase families.
LAD-1, theCaenorhabditis elegansL1CAM homologue, participates in embryonic and gonadal morphogenesis and is a substrate for fibroblast growth factor receptor pathway-dependent phosphotyrosine-based signaling
Authors: Chen Lihsia , Ong Bryan , Bennett Vann
Published: July 2002

This study shows that L1-like adhesion (LAD-1), the sole Caenorhabditis elegans homologue of the L1 family of neuronal adhesion molecules, is required for proper development of the germline and the early embryo and embryonic and gonadal morphogenesis. In addition, the ubiquitously expressed LAD-1, which binds to ankyrin-G, colocalizes with the C. elegans ankyrin, UNC-44, in multiple tissues at sites of cell–cell contact. Finally, we show that LAD-1 is phosphorylated in a fibroblast growth factor receptor (FGFR) pathway-dependent manner on a tyrosine residue in the highly conserved ankyrin-binding motif, FIGQY, which was shown previously to abolish the L1 family of cell adhesion molecule (L1CAM) binding to ankyrin in cultured cells. Immunofluorescence studies revealed that FIGQY-tyrosine–phosphorylated LAD-1 does not colocalize with nonphosphorylated LAD-1 or UNC-44 ankyrin but instead is localized to sites that undergo mechanical stress in polarized epithelia and axon–body wall muscle junctions. These findings suggest a novel ankyrin-independent role for LAD-1 related to FGFR signaling. Taken together, these results indicate that L1CAMs constitute a family of ubiquitous adhesion molecules, which participate in tissue morphogenesis and maintaining tissue integrity in metazoans.