Richard Lin

Distinct domains of syntaxin are required for synaptic vesicle fusion complex formation and dissociation.

Membrane fusion resulting in neurotransmitter secretion forms the basis of neural communication. Three multimeric complexes of the protein syntaxin are important in this process: syntaxin and n-sec1; syntaxin, VAMP, and SNAP-25; and syntaxin, VAMP, SNAP-25, alpha SNAP, and NSF (20S complex). In this report, we demonstrate that unique, yet overlapping, domains of syntaxin are required to form these complexes. The formation of higher order heteromultimers has a set of structural requirements distinct from those required for dimeric interactions. Dissociation of the 20S complex by NSF following ATP hydrolysis requires amino-terminal regions of syntaxin that are outside of the binding domains for the 20S constituent proteins. These data are consistent with the hypothesis that conformational changes in syntaxin, resulting from protein-protein interactions and ATP hydrolysis by NSF, mediate neurotransmitter release.

A New Syntaxin Family Member Implicated in Targeting of Intracellular Transport Vesicles

Despite the central role vesicular trafficking occupies in protein targeting, the molecular coding of the trafficking signals and the mechanism of vesicle docking and fusion are just beginning to be understood. We report here the cloning and initial characterization of a new member of the syntaxin family of vesicular transport receptors. Syntaxin 6 is a 255-amino acid protein with two domains predicted to form coiled-coils, as well as a carboxyl-terminal membrane anchor. Syntaxin 6 is broadly expressed and localizes in the region of the Golgi apparatus. In vitro binding studies established that syntaxin 6 binds to α-soluble NSF attachment protein (α-SNAP). The sequence homology, topology, localization, and α-SNAP binding suggest that syntaxin 6 is involved in intracellular vesicle trafficking.

An integrated data analysis approach to characterize genes highly expressed in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the major causes of cancer deaths worldwide. New diagnostic and therapeutic options are needed for more effective and early detection and treatment of this malignancy. We identified 703 genes that are highly expressed in HCC using DNA microarrays, and further characterized them in order to uncover novel tumor markers, oncogenes, and therapeutic targets for HCC. Using Gene Ontology annotations, genes with functions related to cell proliferation and cell cycle, chromatin, repair, and transcription were found to be significantly enriched in this list of highly expressed genes. We also identified a set of genes that encode secreted (e.g. GPC3, LCN2, and DKK1) or membrane-bound proteins (e.g. GPC3, IGSF1, and PSK-1), which may be attractive candidates for the diagnosis of HCC. A significant enrichment of genes highly expressed in HCC was found on chromosomes 1q, 6p, 8q, and 20q, and we also identified chromosomal clusters of genes highly expressed in HCC. The microarray analyses were validated by RT–PCR and PCR. This approach of integrating other biological information with gene expression in the analysis helps select aberrantly expressed genes in HCC that may be further studied for their diagnostic or therapeutic utility.

Replacement of Threonine 558, a Critical Site of Phosphorylation of Moesin in Vivo, with Aspartate Activates F-actin Binding of Moesin REGULATION BY CONFORMATIONAL CHANGE

Point and deletion mutants of moesin were examined for F-actin binding by blot overlay and co-sedimentation, and for intra- and intermolecular interactions with N- and C-terminal domains with yeast two-hybrid and in vitro binding assays. Wild-type moesin molecules interact poorly with F-actin and each other, and bind neither C- nor N-terminal fragments. Interaction with F-actin is strongly enhanced by replacement of Thr558 with aspartate (T558D), by deletion of 11 N-terminal residues (DelN11), by deletion of the entire N-terminal membrane-binding domain of both wild type and T558D mutant molecules, and by exposure to phosphatidylinositol 4,5-diphosphate. Activation of F-actin binding is accompanied by changes in inter- and intramolecular domain interactions. The T558D mutation renders moesin capable of binding wild type but not mutated (T558D) C-terminal or wild type N-terminal fragments. The interaction between the latter two is prevented. DelN11 truncation enables binding of wild type N and C domain fragments. These changes suggest that the T558D mutation, mimicking phosphorylation of Thr558, promotes F-actin binding by disruption of interdomain interactions between N and C domains and exposure of the high affinity F-actin binding site in the C-terminal domain. Oscillation between activated and resting state could thus provide the structural basis for transient interactions between moesin and the actin cytoskeleton in protruding and retracting microextensions.

Glioma cells on the run – the migratory transcriptome of 10 human glioma cell lines

BackgroundGlioblastoma multiforme (GBM) is the most common primary intracranial tumor and despite recent advances in treatment regimens, prognosis for affected patients remains poor. Active cell migration and invasion of GBM cells ultimately lead to ubiquitous tumor recurrence and patient death.To further understand the genetic mechanisms underlying the ability of glioma cells to migrate, we compared the matched transcriptional profiles of migratory and stationary populations of human glioma cells. Using a monolayer radial migration assay, motile and stationary cell populations from seven human long term glioma cell lines and three primary GBM cultures were isolated and prepared for expression analysis.ResultsGene expression signatures of stationary and migratory populations across all cell lines were identified using a pattern recognition approach that integrates a priori knowledge with expression data. Principal component analysis (PCA) revealed two discriminating patterns between migrating and stationary glioma cells: i) global down-regulation and ii) global up-regulation profiles that were used in a proband-based rule function implemented in GABRIEL to find subsets of genes having similar expression patterns. Genes with up-regulation pattern in migrating glioma cells were found to be overexpressed in 75% of human GBM biopsy specimens compared to normal brain. A 22 gene signature capable of classifying glioma cultures based on their migration rate was developed. Fidelity of this discovery algorithm was assessed by validation of the invasion candidate gene, connective tissue growth factor (CTGF). siRNA mediated knockdown yielded reduced in vitro migration and ex vivo invasion; immunohistochemistry on glioma invasion tissue microarray confirmed up-regulation of CTGF in invasive glioma cells.ConclusionGene expression profiling of migratory glioma cells induced to disperse in vitro affords discovery of genomic signatures; selected candidates were validated clinically at the transcriptional and translational levels as well as through functional assays thereby underscoring the fidelity of the discovery algorithm.

Closed-Eye Ocular Injuries in the Iraq and Afghanistan Wars

Comprehensive ophthalmic evaluation was conducted in 46 veterans hospitalized because of traumatic brain injury after blast exposure in Iraq or Afghanistan. Evidence of closed-eye injury was found in 20 of these patients.

Regulation of morphological differentiation in S. coelicolor by RNase III (AbsB) cleavage of mRNA encoding the AdpA transcription factor

RNase III family enzymes, which are perhaps the most widely conserved of all ribonucleases, are known primarily for their role in the processing and maturation of small RNAs. The RNase III gene of Streptomyces coelicolor, which was discovered initially as a global regulator of antibiotic production in this developmentally complex bacterial species and named absB (antibiotic biosynthesis gene B), has subsequently also been found to modulate the cellular abundance of multiple messenger RNAs implicated in morphological differentiation. We report here that regulation of differentiation‐related mRNAs by the S. coelicolor AbsB/RNase III enzyme occurs largely by ribonucleolytic cleavage of transcripts encoding the pleiotropic transcription factor, AdpA, and that AdpA and AbsB participate in a novel feedback‐control loop that reciprocally regulates the cellular levels of both proteins. Our results reveal a previously unsuspected mechanism for global ribonuclease‐mediated control of gene expression in streptomycetes.

Alternative activation in systemic juvenile idiopathic arthritis monocytes

Systemic juvenile idiopathic arthritis (SJIA) is a chronic autoinflammatory condition. The association with macrophage activation syndrome, and the therapeutic efficacy of inhibiting monocyte-derived cytokines, has implicated these cells in SJIA pathogenesis. To characterize the activation state (classical/M1 vs. alternative/M2) of SJIA monocytes, we immunophenotyped monocytes using several approaches. Monocyte transcripts were analyzed by microarray and quantitative PCR. Surface proteins were measured at the single cell level using flow cytometry. Cytokine production was evaluated by intracellular staining and ELISA. CD14(++)CD16(-) and CD14(+)CD16(+) monocyte subsets are activated in SJIA. A mixed M1/M2 activation phenotype is apparent at the single cell level, especially during flare. Consistent with an M2 phenotype, SJIA monocytes produce IL-1β after LPS exposure, but do not secrete it. Despite the inflammatory nature of active SJIA, circulating monocytes demonstrate significant anti-inflammatory features. The persistence of some of these phenotypes during clinically inactive disease argues that this state reflects compensated inflammation.

Barriers to Follow-Up and Strategies to Improve Adherence to Appointments for Care of Chronic Eye Diseases.

PURPOSE To understand factors associated with poor attendance of follow-up appointments for care of glaucoma (GL), AMD, and diabetic retinopathy (DR) in a tertiary referral center, and to identify strategies to improve adherence. METHODS Cross-sectional study of 240 adults attending follow-up appointments for GL, AMD, or DR. Cases (N = 102) were patients with poor follow-up who missed and failed to reschedule an appointment within 1 month of the recommended follow-up date during the preceding year. Controls (N = 138) were patients who completed the assigned follow-up. Data regarding the factors impacting adherence to appointments were collected via an orally administered questionnaire. Multivariate logistic regression was performed to determine factors associated with poor follow-up. RESULTS In a multivariate logistic regression model, independent factors significantly associated with poor follow-up included incorrectly answering more than 50% of questions about eye disease (adjusted odds ratio [OR] = 3.24, P = 0.001), legal blindness (adjusted OR 2.64, P = 0.013), the presence of glaucomatous versus retinal disease (adjusted OR 2.06, P = 0.013), and difficulty for the study subject and/or escort taking time away from work for the appointments (adjusted OR 1.80, P = 0.049). Subjects identified the following strategies to improve follow-up: contact with others having the same eye condition (41.3%), greater education regarding eye disease (40.8%), and improved transportation services to the clinic (44.6%). CONCLUSIONS Low disease knowledge scores, legal blindness, and difficulty getting time away from work for appointments adversely impacted follow-up independent of eye disease diagnosis. Improvements in patient education, transportation services, and clinic efficiency may increase adherence to recommended appointment intervals.

Correlation analyses of clinical and molecular findings identify candidate biological pathways in systemic juvenile idiopathic arthritis

BackgroundClinicians have long appreciated the distinct phenotype of systemic juvenile idiopathic arthritis (SJIA) compared to polyarticular juvenile idiopathic arthritis (POLY). We hypothesized that gene expression profiles of peripheral blood mononuclear cells (PBMC) from children with each disease would reveal distinct biological pathways when analyzed for significant associations with elevations in two markers of JIA activity, erythrocyte sedimentation rate (ESR) and number of affected joints (joint count, JC).MethodsPBMC RNA from SJIA and POLY patients was profiled by kinetic PCR to analyze expression of 181 genes, selected for relevance to immune response pathways. Pearson correlation and Students t-test analyses were performed to identify transcripts significantly associated with clinical parameters (ESR and JC) in SJIA or POLY samples. These transcripts were used to find related biological pathways.ResultsCombining Pearson and t-test analyses, we found 91 ESR-related and 92 JC-related genes in SJIA. For POLY, 20 ESR-related and 0 JC-related genes were found. Using Ingenuity Systems Pathways Analysis, we identified SJIA ESR-related and JC-related pathways. The two sets of pathways are strongly correlated. In contrast, there is a weaker correlation between SJIA and POLY ESR-related pathways. Notably, distinct biological processes were found to correlate with JC in samples from the earlier systemic plus arthritic phase (SAF) of SJIA compared to samples from the later arthritis-predominant phase (AF). Within the SJIA SAF group, IL-10 expression was related to JC, whereas lack of IL-4 appeared to characterize the chronic arthritis (AF) subgroup.ConclusionsThe strong correlation between pathways implicated in elevations of both ESR and JC in SJIA argues that the systemic and arthritic components of the disease are related mechanistically. Inflammatory pathways in SJIA are distinct from those in POLY course JIA, consistent with differences in clinically appreciated target organs. The limited number of ESR-related SJIA genes that also are associated with elevations of ESR in POLY implies that the SJIA associations are specific for SJIA, at least to some degree. The distinct pathways associated with arthritis in early and late SJIA raise the possibility that different immunobiology underlies arthritis over the course of SJIA.