Cloning, Mapping, and Characterization of the Human Sorbin and SH3 Domain Containing 1 (SORBS1) Gene: A Protein Associated with c-Abl during Insulin Signaling in the Hepatoma Cell Line Hep3B

Novel Genetic Risk Variants Associated with Oral Tongue Squamous Cell Carcinoma

PURPOSE

Limited data from genome-wide association studies (GWAS) focusing on oral tongue squamous cell carcinoma (OTSCC) are available. The present study was conducted to explore genetic associations for OTSCC.

METHODS

A GWAS on 376 cases of OTSCC was conducted using the FinnGen Data Freeze-12 dataset. The case-cohort included 205 males and 171 females. Cases with malignancies involving the base of the tongue or lingual tonsil were excluded from the case-cohort. Individuals with no recorded history of malignancy were used as controls (n = 407,067). A Phenome-wide association study (PheWAS) was performed for the lead variants to assess their co-associations with other cancers.

RESULTS

GWAS analysis identified three genome-wide significant loci associated with OTSCC (p < 5 × 10-8), located at 5p15.33 (rs27067 near gene LINC01511), 10q24 (rs1007771191 near RPS3AP36), and 20p12.3 (rs1438070080 near PLCB1), respectively. PheWAS showed associations of rs27067 mainly with prostate cancer (OR = 1.06, p = 5.41 × 10-7), and seborrheic keratosis (OR = 1.11, p = 1.51 × 10-11). A co-directional effect with melanoma was also observed (OR = 0.93, p = 6.24 × 10-5).

CONCLUSION

The GWAS detected two novel genetic associations with OTSCC. Further research is needed to identify the genes at these loci that contribute to the molecular pathogenesis of OTSCC.

Identification of a Potential PGK1 Inhibitor with the Suppression of Breast Cancer Cells Using Virtual Screening and Molecular Docking

BACKGROUND/OBJECTIVES

Breast cancer is the second most common malignancy worldwide and poses a significant threat to women's health. However, the prognostic biomarkers and therapeutic targets of breast cancer are unclear. A prognostic model can help in identifying biomarkers and targets for breast cancer. In this study, a novel prognostic model was developed to optimize treatment, improve clinical prognosis, and screen potential phosphoglycerate kinase 1 (PGK1) inhibitors for breast cancer treatment.

METHODS

Using data from the Gene Expression Omnibus (GEO) database, differentially expressed genes (DEGs) were identified in normal individuals and breast cancer patients. The biological functions of the DEGs were examined using bioinformatics analysis. A novel prognostic model was then constructed using the DEGs through LASSO and multivariate Cox regression analyses. The relationship between the prognostic model, survival, and immunity was also evaluated. In addition, virtual screening was conducted based on the risk genes to identify novel small molecule inhibitors of PGK1 from Chemdiv and Targetmol libraries. The effects of the potential inhibitors were confirmed through cell experiments.

RESULTS

A total of 230 up- and 325 down-regulated DEGs were identified in HER2, LumA, LumB, and TN breast cancer subtypes. A new prognostic model was constructed using ten risk genes. The analysis from The Cancer Genome Atlas (TCGA) indicated that the prognosis was poorer in the high-risk group compared to the low-risk group. The accuracy of the model was confirmed using the ROC curve. Furthermore, functional enrichment analyses indicated that the DEGs between low- and high-risk groups were linked to the immune response. The risk score was also correlated with tumor immune infiltrates. Moreover, four compounds with the highest score and the lowest affinity energy were identified. Notably, D231-0058 showed better inhibitory activity against breast cancer cells.

CONCLUSIONS

Ten genes (ACSS2, C2CD2, CXCL9, KRT15, MRPL13, NR3C2, PGK1, PIGR, RBP4, and SORBS1) were identified as prognostic signatures for breast cancer. Additionally, results showed that D231-0058 (2-((((4-(2-methyl-1H-indol-3-yl)-1,3-thiazol-2-yl)carbamoyl)methyl)sulfanyl)acetic acid) may be a novel candidate for treating breast cancer.

Temporal regulation of gene expression through integration of p53 dynamics and modifications

The master regulator of the DNA damage response, the transcription factor p53, orchestrates multiple downstream responses and coordinates repair processes. In response to double-strand DNA breaks, p53 exhibits pulses of expression, but how it achieves temporal coordination of downstream responses remains unclear. Here, we show that p53's posttranslational modification state is altered between its first and second pulses of expression. We show that acetylations at two sites, K373 and K382, were reduced in the second pulse, and these acetylations differentially affected p53 target genes, resulting in changes in gene expression programs over time. This interplay between dynamics and modification may offer a strategy for cellular hubs like p53 to temporally organize multiple processes in individual cells.

Genome-wide mapping of the binding sites of myocyte enhancer factor 2A in chicken primary myoblasts

Myocyte enhancer factor 2A (MEF2A) is a transcription factor that plays a critical role in cell proliferation, differentiation and apoptosis. In contrast to the wide characterization of its regulation mechanism in mammalian skeletal muscle, its role in chickens is limited. Especially, its wide target genes remain to be identified. Therefore, we utilized Cleavage Under Targets and Tagmentation (CUT&Tag) technology to reveal the genome-wide binding profile of MEF2A in chicken primary myoblasts thus gaining insights into its potential role in muscle development. Our results revealed that MEF2A binding sites were primarily distributed in intergenic and intronic regions. Within the promoter region, although only 8.87% of MEF2A binding sites were found, these binding sites were concentrated around the transcription start site (TSS). Following peak annotation, a total of 1903 genes were identified as potential targets of MEF2A. Gene Ontology (GO) enrichment analysis further revealed that MEF2A target genes may be involved in the regulation of embryonic development in multiple organ systems, including muscle development, gland development, and visual system development. Moreover, a comparison of the MEF2A target genes identified in chicken primary myoblasts with those in mouse C2C12 cells revealed 388 target genes are conserved across species, 1515 target genes are chicken specific. Among these conserved genes, ankyrin repeat and SOCS box containing 5 (ASB5), transmembrane protein 182 (TMEM182), myomesin 2 (MYOM2), leucyl and cystinyl aminopeptidase (LNPEP), actinin alpha 2 (ACTN2), sorbin and SH3 domain containing 1 (SORBS1), ankyrin 3 (ANK3), sarcoglycan delta (SGCD), and ORAI calcium release-activated calcium modulator 1 (ORAI1) exhibited consistent expression patterns with MEF2A during embryonic muscle development. Finally, TMEM182, as an important negative regulator of muscle development, has been validated to be regulated by MEF2A by dual-luciferase and quantitative real-time PCR (qPCR) assays. In summary, our study for the first time provides a wide landscape of MEF2A target genes in chicken primary myoblasts, which supports the active role of MEF2A in chicken muscle development.

Tirzepatide prevents neurodegeneration through multiple molecular pathways

BACKGROUND

Several evidence demonstrated that glucagon-like peptide 1 receptor agonists (GLP1-RAs) reduce the risk of dementia in type 2 diabetes patients by improving memory, learning, and overcoming cognitive impairment. In this study, we elucidated the molecular processes underlying the protective effect of Tirzepatide (TIR), a dual glucose-dependent insulinotropic polypeptide receptor agonist (GIP-RA)/ GLP-1RA, against learning and memory disorders.

METHODS

We investigated the effects of TIR on markers of neuronal growth (CREB and BDNF), apoptosis (BAX/Bcl2 ratio) differentiation (pAkt, MAP2, GAP43, and AGBL4), and insulin resistance (GLUT1, GLUT4, GLUT3 and SORBS1) in a neuroblastoma cell line (SHSY5Y) exposed to normal and high glucose concentration. The potential role on DNA methylation of genes involved in neuroprotection and epigenetic modulators of neuronal growth (miRNA 34a), apoptosis (miRNA 212), and differentiation (miRNA 29c) was also investigated. The cell proliferation was detected by measuring Ki-67 through flow cytometry. The data were analysed by SPSS IBM Version 23 or GraphPad Prism 7.0 software and expressed as the means ± SEM. Differences between the mean values were considered significant at a p-value of < 0.05. GraphPad Prism software was used for drawing figures.

RESULTS

For the first time, it was highlighted: (a) the role of TIR in the activation of the pAkt/CREB/BDNF pathway and the downstream signaling cascade; (b) TIR efficacy in neuroprotection; (c) TIR counteracting of hyperglycemia and insulin resistance-related effects at the neuronal level.

CONCLUSIONS

We demonstrated that TIR can ameliorate high glucose-induced neurodegeneration and overcome neuronal insulin resistance. Thus, this study provides new insight into the potential role of TIR in improving diabetes-related neuropathy.

CBL/CAP Is Essential for Mitochondria Respiration Complex I Assembly and Bioenergetics Efficiency in Muscle Cells

CBL is rapidly phosphorylated upon insulin receptor activation. Mice whole body CBL depletion improved insulin sensitivity and glucose clearance; however, the precise mechanisms remain unknown. We depleted either CBL or its associated protein SORBS1/CAP independently in myocytes and assessed mitochondrial function and metabolism compared to control cells. CBL- and CAP-depleted cells showed increased mitochondrial mass with greater proton leak. Mitochondrial respiratory complex I activity and assembly into respirasomes were reduced. Proteome profiling revealed alterations in proteins involved in glycolysis and fatty acid degradation. Our findings demonstrate CBL/CAP pathway couples insulin signaling to efficient mitochondrial respiratory function and metabolism in muscle.

Androgen plays an important role in regulating the synthesis of pheromone in the scent gland of muskrat

The scent (musk) gland is an organ unique to muskrats and other scent-secreting animals, and the pheromones (musk) synthesized and secreted by the scent gland play a role in chemical communication among scent-secreting animals. The musk gland is synchronized with testicular developmental changes; however, little is known regarding androgen secretion from the testis and how this regulates pheromone synthesis and the secretion of scent. To investigate the effect of androgens on the synthesis of pheromones in the musk gland, we established a muskrat castration model by surgical removal of the testis, and analyzed the histomorphology, hormone concentration, gene expression, and changes in the chemical composition of the musk gland in castration and control groups by histomorphological analysis, Enzyme-Linked ImmunoSorbent Assay (ELISA), RNA sequencing (RNA-seq), and gas chromatography-mass spectrometry (GCMS). Histomorphological analysis results showed that after castration, muskrat gland cells underwent significant atrophy (P < 0.05). Hormone measurement results showed that there was a significant decrease in serum testosterone and muskrat musk testosterone (P < 0.05) after muskrat castration. Transcriptome sequencing results showed that 510 differentially expressed transcripts (DETs) were mainly enriched in fatty acid metabolism, terpenoid backbone biosynthesis, fatty acid degradation, PPAR signaling pathway, and fatty acid biosynthesis. GCMS results showed that macrocyclic ketones, steroids, fatty acids, alcohols, and esters in musk were significantly changed (P < 0.05). In conclusion, androgens were found to play an important function in the chemical communication exchange between muskrats through regulating pheromone synthesis in musk cells. This study provides a basis for understanding the mechanism of animal communication influenced by androgens.

Isoform-specific functions of synaptopodin-2 variants in cytoskeleton stabilization and autophagy regulation in muscle under mechanical stress

Protein homeostasis (proteostasis) in multicellular organisms depends on the maintenance of force-bearing and force-generating cellular structures. Within myofibrillar Z-discs of striated muscle, isoforms of synaptopodin-2 (SYNPO2/myopodin) act as adapter proteins that are engaged in proteostasis of the actin-crosslinking protein filamin C (FLNc) under mechanical stress. SYNPO2 directly binds F-actin, FLNc and α-actinin and thus contributes to the architectural features of the actin cytoskeleton. By its association with autophagy mediating proteins, i.e. BAG3 and VPS18, SYNPO2 is also engaged in protein quality control and helps to target mechanical unfolded and damaged FLNc for degradation. Here we show that deficiency of all SYNPO2-isoforms in myotubes leads to decreased myofibrillar stability and deregulated autophagy under mechanical stress. In addition, isoform-specific proteostasis functions were revealed. The PDZ-domain containing variant SYNPO2b and the shorter, PDZ-less isoform SYNPO2e both localize to Z-discs. Yet, SYNPO2e is less stably associated with the Z-disc than SYNPO2b, and is dynamically transferred into FLNc-containing myofibrillar lesions under mechanical stress. SYNPO2e also recruits BAG3 into these lesions via interaction with the WW domain of BAG3. Our data provide evidence for a role of myofibrillar lesions as a transient quality control compartment essential to prevent and repair contraction-induced myofibril damage in muscle and indicate an important coordinating activity for SYNPO2 therein.

Long Non-coding RNAs LOC100126784 and POM121L9P Derived From Bone Marrow Mesenchymal Stem Cells Enhance Osteogenic Differentiation via the miR-503-5p/SORBS1 Axis

Long non-coding RNAs (lncRNAs) play pivotal roles in mesenchymal stem cell differentiation. However, the mechanisms by which non-coding RNA (ncRNA) networks regulate osteogenic differentiation remain unclear. Therefore, our aim was to identify RNA-associated gene and transcript expression profiles during osteogenesis in bone marrow mesenchymal stem cells (BMSCs). Using transcriptome sequencing for differentially expressed ncRNAs and mRNAs between days 0 and 21 of osteogenic differentiation of BMSCs, we found that the microRNA (miRNA) miR-503-5p was significantly downregulated. However, the putative miR-503-5p target, sorbin and SH3 domain containing 1 (SORBS1), was significantly upregulated in osteogenesis. Moreover, through lncRNA-miRNA-mRNA interaction analyses and loss- and gain-of-function experiments, we discovered that the lncRNAs LOC100126784 and POM121L9P were abundant in the cytoplasm and enhanced BMSC osteogenesis by promoting SORBS1 expression. In contrast, miR-503-5p reversed this effect. Ago2 RNA-binding protein immunoprecipitation and dual-luciferase reporter assays further validated the direct binding of miR-503-5p to LOC100126784 and POM121L9P. Furthermore, SORBS1 knockdown suppressed early osteogenic differentiation in BMSCs, and co-transfection with SORBS1 small interfering RNAs counteracted the BMSCs’ osteogenic capacity promoted by LOC100126784- and POM121L9P-overexpressing lentivirus plasmids. Thus, the present study demonstrated that the lncRNAs LOC100126784 and POM121L9P facilitate the osteogenic differentiation of BMSCs via the miR-503-5p/SORBS1 axis, providing potential therapeutic targets for treating osteoporosis and bone defects.

Discovery and validation of novel protein markers in mucosa of portal hypertensive gastropathy

Background

Portal hypertension induced esophageal and gastric variceal bleeding is the main cause of death among patients of decompensated liver cirrhosis. Therefore, a standardized, biomarker-based test, to make an early-stage non-invasive risk assessment of portal hypertension, is highly desirable. However, no fit-for-purpose biomarkers have yet been identified.

Methods

We conducted a pilot study consisting of 5 portal hypertensive gastropathy (PHG) patients and 5 normal controls, sampling the gastric mucosa of normal controls and PHG patients before and after endoscopic cyanoacrylate injection, using label-free quantitative (LFQ) mass spectrometry, to identify potential biomarker candidates in gastric mucosa from PHG patients and normal controls. Then we further used parallel reaction monitoring (PRM) to verify the abundance of the targeted protein.

Results

LFQ analyses identified 423 significantly differentially expressed proteins. 17 proteins that significantly elevated in the gastric mucosa of PHG patients were further validated using PRM.

Conclusions

This is the first application of an LFQ-PRM workflow to identify and validate PHG–specific biomarkers in patient gastric mucosa samples. Our findings lay the foundation for comprehending the molecular mechanisms of PHG pathogenesis, and provide potential applications for useful biomarkers in early diagnosis and treatment.

Trial registration and ethics approval: Trial registration was completed (ChiCTR2000029840) on February 25, 2020. Ethics Approvals were completed on July 17, 2017 (NYSZYYEC20180003) and February 15, 2020 (NYSZYYEC20200005).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-021-01787-5.

Transcriptome Analysis Reveals Long Intergenic Non-Coding RNAs Contributed to Intramuscular Fat Content Differences between Yorkshire and Wei Pigs

Intramuscular fat (IMF) content is closely related to various meat traits, such as tenderness, juiciness, and flavor. The IMF content varies considerably among pig breeds with different genetic backgrounds. Long intergenic non-coding RNAs (lincRNAs) have been widely identified in many species and found to be an important class of regulators that can participate in multiple biological processes. However, the mechanism behind lincRNAs regulation of pig IMF content remains unknown and requires further study. In our study, we identified a total of 156 lincRNAs in the longissimus dorsi muscle of Wei (fat-type) and Yorkshire (lean-type) pigs using previously published data. These identified lincRNAs have shorter transcript length, longer exon length, lower exon number, and lower expression level as compared with protein-coding transcripts. We predicted potential target genes (PTGs) that are potentially regulated by lincRNAs in cis or trans regulation. Gene ontology and pathway analyses indicated that many potential lincRNAs target genes are involved in IMF-related processes or pathways, such as fatty acid catabolic process and adipocytokine signaling pathway. In addition, we analyzed quantitative trait locus (QTL) sites that differentially expressed lincRNAs (DE lincRNAs) between Wei and Yorkshire pigs co-localized. The QTL sites where DE lincRNAs co-localize are mostly related to IMF content. Furthermore, we constructed a co-expressed network between DE lincRNAs and their differentially expressed PTGs (DEPTGs). On the basis of their expression levels, we suggest that many DE lincRNAs can affect IMF development by positively or negatively regulating their PTGs. This study identified and analyzed some lincRNAs- and PTGs-related IMF development of the two pig breeds and provided new insight into research on the roles of lincRNAs in the two types of breeds.

Afadin is a scaffold protein repressing insulin action via HDAC6 in adipose tissue

Insulin orchestrates metabolic homeostasis through a complex signaling network for which the precise mechanisms controlling its fine-tuning are not completely understood. Here, we report that Afadin, a scaffold protein, is phosphorylated on S1795 (S1718 in humans) in response to insulin in adipocytes, and this phosphorylation is impaired with obesity and insulin resistance. In turn, loss of Afadin enhances the response to insulin in adipose tissues via upregulation of the insulin receptor protein levels. This happens in a cell-autonomous and phosphorylation-dependent manner. Insulin-stimulated Afadin-S1795 phosphorylation modulates Afadin binding with interaction partners in adipocytes, among which HDAC6 preferentially interacts with phosphorylated Afadin and acts as a key intermediate to suppress insulin receptor protein levels. Adipose tissue-specific Afadin depletion protects against insulin resistance and improves glucose homeostasis in diet-induced obese mice, independently of adiposity. Altogether, we uncover a novel insulin-induced cellular feedback mechanism governed by the interaction of Afadin with HDAC6 to negatively control insulin action in adipocytes, which may offer new strategies to alleviate insulin resistance.

MiR-142-5p Acts as a Significant Regulator Through Promoting Proliferation, Invasion, and Migration in Breast Cancer Modulated by Targeting SORBS1

Background:

Numerous researches have demonstrated that miR-142-5p plays significant roles in several cancers, although the functional characteristic of miR-142-5p in breast cancer has not been determined. This study is designed to explore the biological significance of miR-142-5p in breast cancer clinical implication and mechanism of action.

Methods:

The differential expression patterns of miR-142-5p and Sorbin and SH3 domain-containing protein 1 and correlations between them and clinical significances were analyzed based on data from database. The expression levels of miR-142-5p in breast cancer cells were detected using quantitative real-time polymerase chain reaction. Cell counting kit-8, transwell, and wound healing assays were used to explore the potential functions of miR-142-5p in breast cancer cells. In addition, bioinformatics prediction analysis and luciferase reporter assay were utilized to predict and identify the potential target gene of miR-142-5p. A rescue experiment was conducted by transfecting miR-142-5p inhibitors and si-Sorbin and SH3 domain-containing protein 1 into cells to explore miR-142-5p/Sorbin and SH3 domain-containing protein 1 pairs on breast cancer cells behaviors.

Results:

The analysis results showed that miR-142-5p was highly expressed in patients with breast cancer, while Sorbin and SH3 domain-containing protein 1 presented a trend of low expression. The clinical significances analysis suggested that the overexpression of miR-142-5p is closely correlated with metastasis, while low expression of Sorbin and SH3 domain-containing protein 1 is correlated with clinicopathological characteristics and poor overall survival in patients with breast cancer. In vitro exploration, the expression of miR-142-5p was upregulated in breast cancer cells and inhibition of miR-142-5p expression significantly reduced the proliferation, invasion, and migration of breast cancer cells. Through rescue experiments, breast cancer cells proliferation, invasion, and migration reduction induced by silencing of miR-142-5p were reversed via knockdown Sorbin and SH3 domain-containing protein 1.

Conclusion:

Our findings insinuate that miR-142-5p functions as a positive regulator of promoting breast cancer cells biological behaviors and clinical metastasis, possibly regulated by targeting Sorbin and SH3 domain-containing protein 1, thus providing valuable information in the development of preventive or even therapeutic strategies for utilizing miR-142-5p as a promising target.

Vinexin family (SORBS) proteins regulate mechanotransduction in mesenchymal stem cells

The stiffness of extracellular matrix (ECM) directs the differentiation of mesenchymal stem cells (MSCs) through the transcriptional co-activators Yes-associated protein (YAP) and transcriptional coactivator with a PDZ-binding motif (TAZ). Although a recent study revealed the involvement of vinexin α and CAP (c-Cbl-associated proteins), two of vinexin (SORBS) family proteins that bind to vinculin, in mechanosensing, it is still unclear whether these proteins regulate mechanotransduction and differentiation of MSCs. In the present study, we show that both vinexin α and CAP are necessary for the association of vinculin with the cytoskeleton and the promotion of YAP/TAZ nuclear localization in MSCs grown on rigid substrates. Furthermore, CAP is involved in the MSC differentiation in a stiffness-dependent manner, whereas vinexin depletion suppresses adipocyte differentiation independently of YAP/TAZ. These observations reveal a critical role of vinexin α and CAP in mechanotransduction and MSC differentiation.

Genetic variation of SORBS1 gene is associated with glucose homeostasis and age at onset of diabetes: A SAPPHIRe Cohort Study

The SORBS1 gene plays an important role in insulin signaling. We aimed to examine whether common single-nucleotide polymorphisms (SNPs) of SORBS1 are associated with prevalence and incidence of diabetes, age at onset of diabetes, and the related traits of glucose homeostasis. A total of 1135 siblings from 492 ethnic Chinese families were recruited at baseline, and 630 were followed up for 5.19 ± 0.96 years. Nine SNPs including rs7081076, rs2281939, rs3818540, rs2274490, rs61739184, rs726176, rs2296966, rs17849148, and rs3193970 were genotyped and examined. To deal with correlated data of subjects within the same families, the generalized estimating equations approach was applied throughout all association analyses. The GG genotype of rs2281939 was associated with a higher risk of diabetes at baseline, an earlier onset of diabetes, and higher steady-state plasma glucose levels in the modified insulin suppression test. The minor allele T of rs2296966 was associated with higher prevalence and incidence of diabetes, an earlier onset of diabetes, and higher 2-h glucose during oral glucose tolerance test. These two SNPs revealed independent associations with age of diabetes onset as well as risk of diabetes at baseline. These findings supported that SORBS1 gene participates in the pathogenesis of diabetes.

SORBS1 suppresses tumor metastasis and improves the sensitivity of cancer to chemotherapy drug

Tumor metastasis and invasion are both hallmarks of cancer malignancy and the leading cause of cancer death. Here we show that the adaptor protein SORBS1 (Sorbin and SH3 domain-containing protein 1, also known as CAP/ponsin) is expressed at low levels in clinical cancer samples. In addition, low-level expression of SORBS1 was significantly associated with poor clinical outcomes and the increased tumor cell invasive capacity in breast cancer patients. We demonstrate that depletion of SORBS1 increases protrusions and filopodium-like protrusions (FLPs) formation, as well as the migratory and invasive abilities of cancer cells, via activation of JNK/cJun. Furthermore, silencing of SORBS1 promotes the epithelial-to-mesenchymal transition (EMT) process and attenuates chemical drug sensitivity especially that to cisplatin, by inhibition of p53 in breast cancer cells. Thus, we illustrate that SORBS1 is a potential inhibitor of metastasis in cancer and may be a promising target in chemotherapy.

EsGLUT4 and CHHBP are involved in the regulation of glucose homeostasis in the crustacean Eriocheir sinensis

Glucose is an essential energy source for both vertebrates and invertebrates. In mammals, glucose uptake is mediated primarily by glucose transporters (GLUTs), members of the major facilitator superfamily (MFS) of passive transporters. Among the GLUTs, GLUT4 is the main glucose transporter in muscles and adipocytes. In skeletal muscle cells, GLUT4 interacts with the lipid raft protein flotillin to transport glucose upon stimulation by insulin. Although several studies have examined GLUT4 function in mammals, few have been performed in crustaceans, which also use glucose as their main energy source. Crustacean hyperglycemic hormone (CHH) is a multifunctional neurohormone found only in arthropods, and one of its roles is to regulate glucose homeostasis. However, the molecular mechanism that underlies CHH regulation and whether GLUT4 is involved in its regulation in crustaceans remain unclear. In the present study, we identified a full-length GLUT4 cDNA sequence (defined herein as EsGLUT4) from the Chinese mitten crab Eriocheir sinensis and analyzed its tissue distribution and cellular localization. By the ForteBio Octet system, two large hydrophilic regions within EsGLUT4 were found to interact with the CHH binding protein (CHHBP), an E. sinensis flotillin-like protein. Interestingly, live-cell imaging indicated that EsGLUT4 and CHHBP responded simultaneously upon stimulation by CHH, resulting in glucose release. In contrast to insulin-dependent GLUT4, however, EsGLUT4 and CHHBP were present within cytoplasmic vesicles, both translocating to the plasma membrane upon CHH stimulation. In conclusion, our results provide new evidence for the involvement of EsGLUT4 and CHHBP in the regulation of glucose homeostasis in crustacean carbohydrate metabolism.

Summary: Here we identified that Glucose transporter 4 (GLUT4) could interact with CHH binding protein (CHHBP) to regulate CHH-stimulated glucose release in Eriocheir sinensis.

Vinexin family (SORBS) proteins play different roles in stiffness-sensing and contractile force generation

Vinexin, c-Cbl associated protein (CAP) and Arg-binding protein 2 (ArgBP2) constitute an adaptor protein family called the vinexin (SORBS) family that is targeted to focal adhesions (FAs). Although numerous studies have focused on each of the SORBS proteins and partially elucidated their involvement in mechanotransduction, a comparative analysis of their function has not been well addressed. Here, we established mouse embryonic fibroblasts that individually expressed SORBS proteins and analysed their functions in an identical cell context. Both vinexin-α and CAP co-localized with vinculin at FAs and promoted the appearance of vinculin-rich FAs, whereas ArgBP2 co-localized with α-actinin at the proximal end of FAs and punctate structures on actin stress fibers (SFs), and induced paxillin-rich FAs. Furthermore, both vinexin-α and CAP contributed to extracellular matrix stiffness-dependent vinculin behaviors, while ArgBP2 stabilized α-actinin on SFs and enhanced intracellular contractile forces. These results demonstrate the differential roles of SORBS proteins in mechanotransduction.

A case of a novel mutation in HNF1β-related maturity-onset diabetes of the young type 5 with diabetic kidney disease complication in a Chinese family

AIMS

Precise diagnosis of maturity-onset diabetes of the young (MODY) has proven valuable for understanding mechanism of diabetes and selecting optimal therapy. A proband and her mother with diabetic kidney disease (DKD) were studied to investigate potential genes responsible for diabetes and different severity of DKD between the parent and offspring.

METHODS

The family with suspected MODY underwent mutational analyses by the whole exome sequencing (WES). Candidate pathogenic variants were validated by Sanger sequencing and tested for co-segregation. The clinical parameters of subjects were collected from medical records.

RESULTS

A novel missense heterozygous mutation in exon 4 of the hepatocyte nuclear factor 1β (HNF1β), c.1007A > G (p.H336R), was identified in both the proband and her mother. Moreover, comparing the family's WES results, we found that the proband had acquired a KCNQ1 gene mutation from her father and acquired ACE and SORBS1 gene mutations from her mother. These three genes are known susceptibility genes of DKD and may impose additional effects contributing to DKD severity.

CONCLUSIONS

A novel mutation in HNF1β-MODY was identified in a Chinese family complicated with DKD, and the additional effect of pathogenic variants in susceptibility genes was speculated to contribute to DKD severity.

Cytotoxic Effects of Environmental Toxins on Human Glial Cells

Toxins produced by cyanobacteria and dinoflagellates have increasingly become a public health concern due to their degenerative effects on mammalian tissue and cells. In particular, emerging evidence has called attention to the neurodegenerative effects of the cyanobacterial toxin β-N-methylamino-L-alanine (BMAA). Other toxins such as the neurotoxins saxitoxin and ciguatoxin, as well as the hepatotoxic microcystin, have been previously shown to have a range of effects upon the nervous system. However, the capacity of these toxins to cause neurodegeneration in human cells has not, to our knowledge, been previously investigated. This study aimed to examine the cytotoxic effects of BMAA, microcystin-LR (MC-LR), saxitoxin (STX) and ciguatoxin (CTX-1B) on primary adult human astrocytes. We also demonstrated that α-lipoate attenuated MC-LR toxicity in primary astrocytes and characterised changes in gene expression which could potentially be caused by these toxins in primary astrocytes. Herein, we are the first to show that all of these toxins are capable of causing physiological changes consistent with neurodegeneration in glial cells, via oxidative stress and excitotoxicity, leading to a reduction in cell proliferation culminating in cell death. In addition, MC-LR toxicity was reduced significantly in astrocytes-treated α-lipoic acid. While there were no significant changes in gene expression, many of the probes that were altered were associated with neurodegenerative disease pathogenesis. Overall, this is important in advancing our current understanding of the mechanism of toxicity of MC-LR on human brain function in vitro, particularly in the context of neurodegeneration.

High content image analysis of focal adhesion-dependent mechanosensitive stem cell differentiation

Human mesenchymal stem cells (hMSCs) receive differentiation cues from a number of stimuli, including extracellular matrix (ECM) stiffness. The pathways used to sense stiffness and other physical cues are just now being understood and include proteins within focal adhesions. To rapidly advance the pace of discovery for novel mechanosensitive proteins, we employed a combination of in silico and high throughput in vitro methods to analyze 47 different focal adhesion proteins for cryptic kinase binding sites. High content imaging of hMSCs treated with small interfering RNAs for the top 6 candidate proteins showed novel effects on both osteogenic and myogenic differentiation; Vinculin and SORBS1 were necessary for stiffness-mediated myogenic and osteogenic differentiation, respectively. Both of these proteins bound to MAPK1 (also known as ERK2), suggesting that it plays a context-specific role in mechanosensing for each lineage; validation for these sites was performed. This high throughput system, while specifically built to analyze stiffness-mediated stem cell differentiation, can be expanded to other physical cues to more broadly assess mechanical signaling and increase the pace of sensor discovery.

Transcriptomic Analyses of Adipocyte Differentiation From Human Mesenchymal Stromal-Cells (MSC)

Adipogenesis is a physiological process required for fat-tissue development, mainly involved in regulating the organism energetic-state. Abnormal distribution-changes and dysfunctions in such tissue are associated to different pathologies. Adipocytes are generated from progenitor cells, via a complex differentiating process not yet well understood. Therefore, we investigated differential mRNA and miRNA expression patterns of human mesenchymal stromal-cells (MSC) induced and not induced to differentiate into adipocytes by next (second)-generation sequencing. A total of 2,866 differentially expressed genes (101 encoding miRNA) were identified, with 705 (46 encoding miRNA) being upregulated in adipogenesis. They were related to different pathways, including PPARG, lipid, carbohydrate and energy metabolism, redox, membrane-organelle biosynthesis, and endocrine system. Downregulated genes were related to extracellular matrix and cell migration, proliferation, and differentiation. Analyses of mRNA-miRNA interaction showed that repressed miRNA-encoding genes can act downregulating PPARG-related genes; mostly the PPARG activator (PPARGC1A). Induced miRNA-encoding genes regulate downregulated genes related to TGFB1. These results shed new light to understand adipose-tissue differentiation and physiology, increasing our knowledge about pathologies like obesity, type-2 diabetes and osteoporosis. J. Cell. Physiol. 232: 771-784, 2017. © 2016 Wiley Periodicals, Inc.

Genetic Variation in the Human SORBS1 Gene is Associated With Blood Pressure Regulation and Age at Onset of Hypertension: A SAPPHIRe Cohort Study

Essential hypertension is a complex disease involving multiple genetic and environmental factors. A human gene containing a sorbin homology domain and 3 SH3 domains in the C-terminal region, termed SORBS1, plays a significant role in insulin signaling. We previously found a significant association between the T228A polymorphism and insulin resistance, obesity, and type 2 diabetes. It has been hypothesized that a set of genes responsible for insulin resistance may be closely linked with genes susceptible to the development of hypertension. Identification of insulin resistance-related genetic factors may, therefore, enhance our understanding of essential hypertension. This study aimed to examine whether common SORBS1 genetic variations are associated with blood pressure and age at onset of hypertension in an ethnic Chinese cohort.We genotyped 9 common tagged single nucleotide polymorphisms of the SORBS1 gene in 1136 subjects of Chinese origin from the Stanford Asia-Pacific Program for Hypertension and Insulin Resistance family study. Blood pressure was measured upon enrolment. The associations of the SORBS1 single nucleotide polymorphisms with blood pressure and the presence of hypertension were analyzed with a generalized estimating equation model. We used the false-discovery rate measure Q value with a cutoff <0.1 to adjust for multiple comparisons. In the Cox regression analysis for hypertension-free survival, a robust sandwich variance estimator was used to deal with the within-family correlations with age at onset of hypertension. Gender, body mass index, and antihypertension medication were adjustment covariates in the Cox regression analysis.In this study, genetic variants of rs2281939 and rs2274490 were significantly associated with both systolic and diastolic blood pressure. A genetic variant of rs2274490 was also significantly associated with the presence of hypertension. Furthermore, genetic variants of rs2281939 and rs2274490 were associated with age at onset of hypertension after adjustment for gender, body mass index, and antihypertension medication.In conclusion, we provide evidence for an association between common SORBS1 genetic variations and blood pressure, presence of hypertension, and age at onset of hypertension. The biological mechanism of genetic variation associated with blood pressure regulation needs further investigation.

Genetics of diabetic nephropathy: a long road of discovery

The global prevalence of diabetic nephropathy is rising in parallel with the increasing incidence of diabetes in most countries. Unfortunately, up to 40 % of persons diagnosed with diabetes may develop kidney complications. Diabetic nephropathy is associated with substantially increased risks of cardiovascular disease and premature mortality. An inherited susceptibility to diabetic nephropathy exists, and progress is being made unravelling the genetic basis for nephropathy thanks to international research collaborations, shared biological resources and new analytical approaches. Multiple epidemiological studies have highlighted the clinical heterogeneity of nephropathy and the need for better phenotyping to help define important subgroups for analysis and increase the power of genetic studies. Collaborative genome-wide association studies for nephropathy have reported unique genes, highlighted novel biological pathways and suggested new disease mechanisms, but progress towards clinically relevant risk prediction models for diabetic nephropathy has been slow. This review summarises the current status, recent developments and ongoing challenges elucidating the genetics of diabetic nephropathy.

Differential gene expression of the key signalling pathway in para-carcinoma, carcinoma and relapse human pancreatic cancer

Pancreatic cancer (PC) has a high rate of mortality and a poorly understood mechanism of progression. Investigation of the molecular mechanism of PC and exploration of the specific markers for early diagnosis and specific targets of therapy are key points to prevent and treat PC effectively and to improve their prognosis. In our study, expression profiles experiment of para-carcinoma, carcinoma and relapse human PC was performed using Agilent human whole genomic oligonucleotide microarrays with 45 000 probes. Differentially expressed genes related with PC were screened and analysed further by Gene Ontology term analysis and Kyoto encyclopaedia of genes and genomes pathway analysis. Our results showed that there were 3853 differentially expressed genes associated with pancreatic carcinogenesis and relapse. In addition, our study found that PC was related to the Jak-STAT signalling pathway, PPAR signalling pathway and Calcium signalling pathway, indicating their potential roles in pancreatic carcinogenesis and progress.

Inputs and outputs of insulin receptor

The insulin receptor (IR) is an important hub in insulin signaling and its activation is tightly regulated. Upon insulin stimulation, IR is activated through autophosphorylation, and consequently phosphorylates several insulin receptor substrate (IRS) proteins, including IRS1-6, Shc and Gab1. Certain adipokines have also been found to activate IR. On the contrary, PTP, Grb and SOCS proteins, which are responsible for the negative regulation of IR, are characterized as IR inhibitors. Additionally, many other proteins have been identified as IR substrates and participate in the insulin signaling pathway. To provide a more comprehensive understanding of the signals mediated through IR, we reviewed the upstream and downstream signal molecules of IR, summarized the positive and negative modulators of IR, and discussed the IR substrates and interacting adaptor proteins. We propose that the molecular events associated with IR should be integrated to obtain a better understanding of the insulin signaling pathway and diabetes.

Structural basis for recognition of the third SH3 domain of full-length R85 (R85FL)/ponsin by ataxin-7

Ataxin-7 (Atx7) is a component of the nuclear transcription co-activator complex; its polyglutamine (polyQ) expansion may cause nuclear accumulation and recruit numerous proteins to the intranuclear inclusion bodies. Full-length R85 (R85FL) is such a protein sequestered by polyQ-expanded Atx7. Here, we report that Atx7 specifically interacts with the third SH3 domain (SH3C) of R85FL through its second portion of proline-rich region (PRR). NMR structural analysis of the SH3C domain and its complex with PRR revealed that SH3C contains a large negatively charged surface for binding with the RRTR motif of Atx7. Microscopy imaging demonstrated that sequestration of R85FL by the polyQ-expanded Atx7 in cell is mediated by this specific SH3C-PRR interaction, which is implicated in the pathogenesis of spinocerebellar ataxia 7.

Ponsin interacts with Nck adapter proteins: implications for a role in cytoskeletal remodelling during differentiation of skeletal muscle cells

Skeletal muscle differentiation is a complex process: It is characterised by changes in gene expression and protein composition. Simultaneously, a dramatic remodelling of the cytoskeleton and associated cell-matrix contacts, the costameres, occurs. The expression and localisation of the protein ponsin at cell-matrix contacts marks the establishment of costameres. In this report we show that skeletal muscle cells are characterised by a novel ponsin isoform, which contains a large insertion in its carboxy-terminus. This skeletal muscle-specific module binds the adapter proteins Nck1 and Nck2, and increased co-localisation of ponsin with Nck2 is observed at remodelling cell-matrix contacts of differentiating skeletal muscle cells. Since this ponsin insertion can be phosphorylated, it may adjust the interaction affinity with Nck adapter proteins. The novel ponsin isoform and its interaction with Nck1/2 provide exciting insight into the convergence of signalling pathways at the costameres, and its crucial role for skeletal muscle differentiation and re-generation.

BmCAP, a silkmoth gene encoding multiple protein isoforms characterized by SoHo and SH3 domains: expression analysis during ovarian follicular development

CAP/ArgBP2/vinexin family proteins, adaptor proteins characterized by three SH3 domains at their C-termini and a SoHo domain towards their N-termini, are known to regulate cell adhesion, cytoskeletal organization, and growth factor signaling. Here we present the isolation and ovarian expression of the BmCAP gene which encodes CAP/ArgBP2/vinexin family proteins in the silkmoth, Bombyx mori. Screening for full-length cDNA clones identified three mRNA isoforms, BmCAP-A1, BmCAP-A2 and BmCAP-B, which show expression throughout ovarian follicular development. Using an antibody raised against a unique region between the SoHo and SH3 domains, BmCAP-A protein isoforms were identified that show specific expression in different compartments of the ovarian follicles. Immunofluorescence staining of the cells of the follicular epithelium establishes a dynamic pattern of BmCAP-A protein localization during choriogenesis. During early choriogenesis, BmCAP-A has a diffuse localization in the cytoplasm but could also be found concentrated at the apical and basal sides at the cell-cell junctions. During late choriogenesis, the diffuse cytoplasmic staining of BmCAP-A disappears while the staining pattern at the apical side resembles a blueprint for the eggshell surface structure. We suggest that BmCAP-A isoforms have important functions during ovarian development, which involve not only the traditional roles in actin organization or cell-cell adhesion but also the regulation of secretion of chorion proteins and the sculpting of the chorion surface.

Cbl-associated protein is tyrosine phosphorylated by c-Abl and c-Src kinases

Background

The c-Cbl-associated protein (CAP), also known as ponsin, localizes to focal adhesions and stress fibers and is involved in signaling events. Phosphorylation has been described for the other two members of the sorbin homology family, vinexin and ArgBP2, but no data exist about the putative phosphorylation of CAP. According to previous findings, CAP binds to tyrosine kinase c-Abl. However, it is not known if CAP is a substrate of c-Abl or other tyrosine kinases or if phosphorylation regulates its localization.

Results

We here show that CAP is Tyr phosphorylated by and interacts with both c-Abl and c-Src. One major phosphorylation site, Tyr360, and two minor contributors Tyr326 and Tyr632 were identified as Abl phosphorylation sites, whereas Src preferentially phosphorylates Tyr326 and Tyr360. Phosphorylation of CAP was not necessary for its localization to focal adhesions and stress fibers, but Tyr326Phe substitution alters the function of CAP during cell spreading.

Conclusion

This is the first demonstration of phosphorylation of CAP by any kinase. Our findings suggest that coordinated action of Src and Abl might regulate the function of CAP and reveal a functional role especially for the Src-mediated Tyr phosphorylation of CAP in cell spreading.

Abundant expression of ponsin, a focal adhesion protein, in lens and downregulation of its expression by impaired cytoskeletal signaling

PURPOSE

This study was undertaken to improve understanding of the defective lens developmental changes induced by the transgenic overexpression of the Rho GDP dissociation inhibitor RhoGDIalpha. The study was focused on a single differentially expressed gene encoding ponsin, a cell adhesion interacting signaling adaptor protein.

METHODS

Total RNA extracted from the P7 lenses of Rho GDIalpha transgenic mice was subjected to cDNA microarray analysis. Ponsin distribution in the mouse lenses was determined by immunofluorescence and immunoblot analyses. Interactions among ponsin, actin, and Rho GTPase signaling pathways were explored in lens epithelial cells.

RESULTS

The RhoGDIalpha transgenic mouse lenses revealed a marked downregulation of expression of multiple splice variants of ponsin. Expression of one of the ponsins (U58883) was found to be abundant in normal mouse lenses. Although ponsin was localized predominantly to the focal adhesions in lens epithelial cells, it was distributed to both the epithelium and fibers, with some isoforms being enriched primarily in the Triton X-100-insoluble fraction in lens tissue. Further, whereas constitutively active RhoA induced ponsin clustering at the leading edges, inhibition of Rho kinase and latrunculin treatment were noted to lead to decreases in ponsin protein levels in lens epithelial cells.

CONCLUSIONS

Abundant expression of ponsin, a focal adhesion protein in the lens tissue indicates a potential role for this protein in lens fiber cell migration and adhesion. Ponsin expression appears to be closely dependent on Rho GTPase-regulated integrity of actin cytoskeletal organization.

Association of polymorphisms of SORBS1, GCK and WISP1 with hypertension in community-dwelling Japanese individuals

Although various loci and genes have been implicated in predisposition to hypertension by genetic linkage analyses and candidate gene association studies, the genes that confer susceptibility to this condition remain to be identified definitively. We have now examined the relationships of 22 candidate gene polymorphisms with the prevalence of hypertension and with blood pressure (BP) in a 6-year population-based longitudinal cohort study and observed significant relationships of three polymorphisms of SORBS1, GCK and WISP1 with hypertension. The 2233 subjects (1106 women, 1127 men) were aged 40-79 years and were randomly recruited to a population-based prospective cohort study of aging and age-related diseases in Japan. BP was measured with subjects having rested in the sitting position for at least 15 min. Genotypes for the 682A --> G (Thr228Ala) polymorphism of SORBS1, the -30G --> A polymorphism of GCK and the 2364A --> G polymorphism of WISP1 were determined by melting curve analysis. Longitudinal analysis with a generalized estimating equation revealed that the polymorphisms of SORBS1 and GCK and that of WISP1 were significantly associated with the prevalence of hypertension in women and men, respectively. Longitudinal analysis with a mixed-effect model revealed that the polymorphism of SORBS1 was significantly related to diastolic BP in women and that those of GCK and WISP1 were significantly related to both systolic and diastolic BP in women and men, respectively. These results suggest that SORBS1 and GCK are susceptibility loci for hypertension in Japanese women and that WISP1 is such a locus in men.

Use of SNP-arrays for ChIP assays: computational aspects

The simultaneous genotyping of thousands of single nucleotide polymorphisms (SNPs) in a genome using SNP-Arrays is a very important tool that is revolutionizing genetics and molecular biology. We expanded the utility of this technique by using it following chromatin immunoprecipitation (ChIP) to assess the multiple genomic locations protected by a protein complex recognized by an antibody. The power of this technique is illustrated through an analysis of the changes in histone H4 acetylation, a marker of open chromatin and transcriptionally active genomic regions, which occur during differentiation of human myoblasts into myotubes. The findings have been validated by the observation of a significant correlation between the detected histone modifications and the expression of the nearby genes, as measured by DNA expression microarrays. This chapter focuses on the computational analysis of the data.

c-Abl and insulin receptor signalling

Insulin Receptor (IR) and IGF-I receptor (IGF-IR) are homolog but display distinct functions: IR is mainly metabolic, while IGF-IR is mitogenic. However, in some conditions like foetal growth, cancer and diabetes, IR may display some non-metabolic effects like proliferation and migration. The molecular mechanisms underlying this 'functional switch of IR' have been attributed to several factors including overexpression of ligands and receptors, predominant IR isoform expression, preferential recruitment of intracellular substrates. Here, we report that c-Abl, a cytoplasmic tyrosine kinase regulating several signal transduction pathways, is involved in this functional switch of IR. Indeed, c-Abl tyrosine kinase is involved in IR signalling as it shares with IR some substrates like Tub and SORBS1 and is activated upon insulin stimulation. Inhibition of c-Abl tyrosine kinase by STI571 attenuates the effect of insulin on Akt/GSK-3beta phosphorylation and glycogen synthesis, and at the same time, it enhances the effect of insulin on ERK activation, cell proliferation and migration. This effect of STI571 is specific to c-Abl inhibition, because it does not occur in Abl-null cells and is restored in c-Abl-reconstituted cells. Numerous evidences suggest that focal adhesion kinase (FAK) is involved in mediating this c-Abl effect. First, c-Abl tyrosine kinase activation is concomitant with FAK dephosphorylation in response to insulin, whereas c-Abl inhibition is accompanied by FAK phosphorylation in response to insulin, a response similar to that observed with IGF-I. Second, the c-Abl effects on insulin signalling are not observed in cells devoid of FAK (FAK(-/-) cells). Taken together these results suggest that c-Abl activation by insulin, via a modification of FAK response, may play an important role in directing mitogenic versus metabolic insulin receptor signalling.

A crucial role in cell spreading for the interaction of Abl PxxP motifs with Crk and Nck adaptors

The dynamic reorganization of actin structures helps to mediate the interaction of cells with their environment. The Abl non-receptor tyrosine kinase can modulate actin rearrangement during cell attachment. Here we report that the Abl PxxP motifs, which bind Src homology 3 (SH3) domains, are indispensable for the coordinated regulation of filopodium and focal adhesion formation and cell-spreading dynamics during attachment. Candidate Abl PxxP-motif-binding partners were identified by screening a comprehensive SH3-domain phage-display library. A combination of protein overexpression, silencing, pharmacological manipulation and mutational analysis demonstrated that the PxxP motifs of Abl exert their effects on actin organization by two distinct mechanisms, involving the inhibition of Crk signaling and the engagement of Nck. These results uncover a previously unappreciated role for Abl PxxP motifs in the regulation of cell spreading.

Systematic, genome-wide, sex-specific linkage of cardiovascular traits in French Canadians

The sexual dimorphism of cardiovascular traits, as well as susceptibility to a variety of related diseases, has long been recognized, yet their sex-specific genomic determinants are largely unknown. We systematically assessed the sex-specific heritability and linkage of 539 hemodynamic, metabolic, anthropometric, and humoral traits in 120 French-Canadian families from the Saguenay-Lac-St-Jean region of Quebec, Canada. We performed multipoint linkage analysis using microsatellite markers followed by peak-wide linkage scan based on Affymetrix Human Mapping 50K Array Xba240 single nucleotide polymorphism genotypes in 3 settings, including the entire sample and then separately in men and women. Nearly one half of the traits were age and sex independent, one quarter were both age and sex dependent, and one eighth were exclusively age or sex dependent. Sex-specific phenotypes are most frequent in heart rate and blood pressure categories, whereas sex- and age-independent determinants are predominant among humoral and biochemical parameters. Twenty sex-specific loci passing multiple testing criteria were corroborated by 2-point single nucleotide polymorphism linkage. Several resting systolic blood pressure measurements showed significant genotype-by-sex interaction, eg, male-specific locus at chromosome 12 (male-female logarithm of odds difference: 4.16; interaction P=0.0002), which was undetectable in the entire population, even after adjustment for sex. Detailed interrogation of this locus revealed a 220-kb block overlapping parts of TAO-kinase 3 and SUDS3 genes. In summary, a large number of complex cardiovascular traits display significant sexual dimorphism, for which we have demonstrated genomic determinants at the haplotype level. Many of these would have been missed in a traditional, sex-adjusted setting.

Role of c-Abl in Directing Metabolic versus Mitogenic Effects in Insulin Receptor Signaling

c-Abl is a cytoplasmic tyrosine kinase involved in several signal transduction pathways. Here we report that c-Abl is involved also in insulin receptor signaling. Indeed, c-Abl tyrosine kinase is activated upon insulin stimulation. Inhibition of c-Abl tyrosine kinase by STI571 attenuates the effect of insulin on Akt/GSK-3beta phosphorylation and glycogen synthesis, and at the same time, it enhances the effect of insulin on ERK activation, cell proliferation, and migration. This effect of STI571 is specific to c-Abl inhibition, because it does not occur in Abl-null cells and is restored in c-Abl-reconstituted cells. Numerous evidences suggest that focal adhesion kinase (FAK) is involved in mediating this c-Abl effect. First, anti-phosphotyrosine blots indicate that c-Abl tyrosine kinase activation is concomitant with FAK dephosphorylation in response to insulin, whereas c-Abl inhibition is accompanied by FAK phosphorylation in response to insulin, a response similar to that observed with IGF-I. Second, the c-Abl effects on insulin signaling are not observed in cells devoid of FAK (FAK(-/-) cells). Taken together these results suggest that c-Abl activation by insulin, via a modification of FAK response, may play an important role in directing mitogenic versus metabolic insulin receptor signaling.

Paxillin and ponsin interact in nascent costameres of muscle cells

Muscle differentiation requires the transition from motile myoblasts to sessile myotubes and the assembly of a highly regular contractile apparatus. This striking cytoskeletal remodelling is coordinated with a transformation of focal adhesion-like cell-matrix contacts into costameres. To assess mechanisms underlying this differentiation process, we searched for muscle specific-binding partners of paxillin. We identified an interaction of paxillin with the vinexin adaptor protein family member ponsin in nascent costameres during muscle differentiation, which is mediated by an interaction of the second src homology domain 3 (SH3) domain of ponsin with the proline-rich region of paxillin. To understand the molecular basis of this interaction, we determined the structure of this SH3 domain at 0.83 A resolution, as well as its complex with the paxillin binding peptide at 1.63 A resolution. Upon binding, the paxillin peptide adopts a polyproline-II helix conformation in the complex. Contrary to the charged SH3 binding interface, the peptide contains only non-polar residues and for the first time such an interaction was observed structurally in SH3 domains. Fluorescence titration confirmed the ponsin/paxillin interaction, characterising it further by a weak binding affinity. Transfection experiments revealed further characteristics of ponsin functions in muscle cells: All three SH3 domains in the C terminus of ponsin appeared to synergise in targeting the protein to force-transducing structures. The overexpression of ponsin resulted in altered muscle cell-matrix contact morphology, suggesting its involvement in the establishment of mature costameres. Further evidence for the role of ponsin in the maintenance of mature mechanotransduction sites in cardiomyocytes comes from the observation that ponsin expression was down-regulated in end-stage failing hearts, and that this effect was reverted upon mechanical unloading. These results provide new insights in how low affinity protein-protein interactions may contribute to a fine tuning of cytoskeletal remodelling processes during muscle differentiation and in adult cardiomyocytes.

Identification of a set of KSRP target transcripts upregulated by PI3K-AKT signaling

BACKGROUND

KSRP is a AU-rich element (ARE) binding protein that causes decay of select sets of transcripts in different cell types. We have recently described that phosphatidylinositol 3-kinase/AKT (PI3K-AKT) activation induces stabilization and accumulation of the labile beta-catenin mRNA through an impairment of KSRP function.

RESULTS

Aim of this study was to identify additional KSRP targets whose stability and steady-state levels are enhanced by PI3K-AKT activation. First, through microarray analyses of the AU-rich transcriptome in pituitary alphaT3-1 cells, we identified 34 ARE-containing transcripts upregulated in cells expressing a constitutively active form of AKT1. In parallel, by an affinity chromatography-based technique followed by microarray analyses, 12 mRNAs target of KSRP, additional to beta-catenin, were identified. Among them, seven mRNAs were upregulated in cells expressing activated AKT1. Both steady-state levels and stability of these new KSRP targets were consistently increased by either KSRP knock-down or PI3K-AKT activation.

CONCLUSION

Our study identified a set of transcripts that are targets of KSRP and whose expression is increased by PI3K-AKT activation. These mRNAs encode RNA binding proteins, signaling molecules and a replication-independent histone. The increased expression of these gene products upon PI3K-AKT activation could play a role in the cellular events initiated by this signaling pathway.

Activation of the Cbl insulin signaling pathway in cardiac muscle; Dysregulation in obesity and diabetes

In adipocytes, the Cbl/CAP dependent signaling pathway has been involved in regulating insulin-stimulated glucose uptake. We investigated activation of Cbl and its downstream effector TC10 in cardiac and skeletal muscle of Balb/C mice. Insulin administration resulted in Cbl phosphorylation in cardiac, skeletal muscle, and adipose tissue. Subsequent TC10 activation was detected only in heart and adipose tissue. c-Cbl and CAP gene expression was significantly reduced in the heart tissue of streptozotocin-induced diabetic animals, whereas no change was observed for other components of the pathway. No changes in Cbl expression were detected in hindlimb muscle. In leptin-/- obese mice Cbl expression in heart and adipose tissue was maintained, although insulin-mediated Cbl phosphorylation and subsequent TC10 activation were significantly reduced. In conclusion, our data demonstrate that Cbl/CAP/TC10 insulin signaling pathway is active in cardiac muscle and impaired during obesity and insulin deficiency.

Expression, purification, and characterization of recombinant human flotillin-1 in Escherichia coli

Human flotillin-1 (reggie-2), a major hydrophobic protein of biomembrane microdomain lipid rafts, was cloned and expressed in Escherichia coli with four different fusion tags (hexahistidine, glutathione S-transferase, NusA, and thioredoxin) to increase the yield. The best expressed flotillin-1 with thioredoxin tag was solubilized from inclusion bodies, first purified by immobilized metal affinity column under denaturing condition and direct refolded on column by decreasing urea gradient method. The thioredoxin tag was cleaved by thrombin, and the flotillin-1 protein was further purified by anion exchanger and gel filtration column. The purified protein was verified by denaturing gel electrophoresis and Western blot. The typical yield was 3.4 mg with purity above 98% from 1L culture medium. Using pull-down assay, the interaction of both the recombinant flotillin-1 and the native flotillin-1 from human erythrocyte membranes with c-Cbl-associated protein or neuroglobin was confirmed, which demonstrated that the recombinant proteins were functional active. This is the first report describing expression, purification, and characterization of active recombinant raft specific protein in large quantity and highly purity, which would facilitate further research such as X-ray crystallography.

Differential gene expression in liposarcoma, lipoma, and adipose tissue

Malignant transformation is thought to be associated with changes in the expression of a number of genes, and this alteration in gene expression is felt to be critical to the development of the malignant phenotype. Sarcomas represent a diverse group of tumors derived from cells of mesenchymal origin. Marked heterogeneity exists in the biological behavior of sarcomas, even within histologic subtypes of sarcomas. In an effort to better understand the biology of liposarcomas, gene expression in normal adipose tissue, lipomas, and liposarcomas was examined using the Affymetrix microarray technology. Differences in gene expression were quantified as the fold change in gene expression among the sample sets. Differences in gene expression among normal adipose tissue, lipomas, and liposarcomas were observed. In addition, genes expressed uniquely in liposarcoma among these and 18 other tissue sample sets were identified. Gene sets were devised that allowed the separation of liposarcomas from other samples, and most normal adipose tissue from most lipomas using the Eisen clustering software "Cluster." We conclude that differences in gene expression can be identified among different tumors derived from the adipocyte series. Such differences in gene expression may help differentiate among subtypes of sarcomas, and may also yield clues to the pathophysiology of this heterogeneous group of tumors.

Tyrosine phosphorylation of myosin heavy chain during skeletal muscle differentiation: an integrated bioinformatics approach

BACKGROUND

Previously it has been shown that insulin-mediated tyrosine phosphorylation of myosin heavy chain is concomitant with enhanced association of C-terminal SRC kinase during skeletal muscle differentiation. We sought to identify putative site(s) for this phosphorylation event.

RESULTS

A combined bioinformatics approach of motif prediction and evolutionary and structural analyses identified tyrosines163 and 1856 of the skeletal muscle heavy chain as the leading candidate for the sites of insulin-mediated tyrosine phosphorylation.

CONCLUSION

Our work is suggestive that tyrosine phosphorylation of myosin heavy chain, whether in skeletal muscle or in platelets, is a significant event that may initiate cytoskeletal reorganization of muscle cells and platelets. Our studies provide a good starting point for further functional analysis of MHC phosphor-signalling events within different cells.

A novel isoform of Cbl-associated protein that binds protein kinase A

A novel isoform of Cbl-associated protein (CAP) was identified in a yeast two-hybrid screen for A-kinase anchoring proteins expressed in the heart. CAP is a scaffold protein implicated in insulin signaling and cytoskeleton regulation. The protein kinase A binding site is encoded by a previously unidentified, alternatively spliced exon.

Libraries enriched for alternatively spliced exons reveal splicing patterns in melanocytes and melanomas

It is becoming increasingly clear that alternative splicing enables the complex development and homeostasis of higher organisms. To gain a better understanding of how splicing contributes to regulatory pathways, we have developed an alternative splicing library approach for the identification of alternatively spliced exons and their flanking regions by alternative splicing sequence enriched tags sequencing. Here, we have applied our approach to mouse melan-c melanocyte and B16-F10Y melanoma cell lines, in which 5,401 genes were found to be alternatively spliced. These genes include those encoding important regulatory factors such as cyclin D2, Ilk, MAPK12, MAPK14, RAB4, melastatin 1 and previously unidentified splicing events for 436 genes. Real-time PCR further identified cell line-specific exons for Tmc6, Abi1, Sorbs1, Ndel1 and Snx16. Thus, the ASL approach proved effective in identifying splicing events, which suggest that alternative splicing is important in melanoma development.

cDNA cloning and functional characterization of a novel splice variant of c-Cbl-associated protein from mouse skeletal muscle

c-Cbl-associated protein (CAP) is an SH3-containing adapter protein that binds to the proto-oncogene c-Cbl. Recent work suggests that signaling through these molecules is involved in the regulation of insulin-stimulated glucose uptake in 3T3-L1 adipocytes. Skeletal muscle is the major site of insulin-stimulated glucose disposal but there have been no reports of CAP function in this tissue. Using RT-PCR of mouse skeletal muscle RNA, we discovered a novel splice variant of CAP (CAPSM; GenBank Accession No. AF521593) that is different from the adipocyte form by inclusion of a novel 168 bp fragment. This fragment encodes a peptide sequence that shows very high similarity with exon 25 of the human homologue of CAP (SORBS1). To understand the function of CAPSM in glucose uptake regulation, L6 myotubes were transfected with either CAPSM or a truncated CAPSM devoid of all three SH3-binding domains (CAPDeltaSH3), which prevents CAP association with c-Cbl. Transfection with CAPDeltaSH3 decreased insulin-stimulated 2-deoxyglucose (2-DG) uptake and reduced c-Cbl phosphorylation. In contrast, transfection of L6 myotubes with CAPDeltaSH3 had no effect on dinitrophenol (DNP)- or hypoxia-stimulated glucose uptake, stimuli that work through insulin-independent mechanisms for the regulation of glucose uptake. These data demonstrate the existence of a novel CAP isoform expressed in skeletal muscle, and suggest the involvement of the CAP/Cbl pathway in the regulation of insulin-stimulated glucose uptake in L6 myotubes.

Frequency of the T228A polymorphism in the SORBS1 gene in children with premature pubarche and in adolescent girls with hyperandrogenism

OBJECTIVE

Because the metabolic actions of insulin are more impaired than the mitogenic pathways in polycystic ovary syndrome (PCOS), genes coding for proteins involved in insulin-mediated glucose transport can be considered as candidate genes. The sorbin and SH3-domain-containing-1 (SORBS1) gene codes for c-Cbl-associated protein (CAP) involved in insulin-mediated glucose uptake. An association study showed that a missense variant of the SORBS1 gene is protective against obesity and diabetes. We tested the hypothesis that the frequency of the protective allele would be decreased in children with premature pubarche and adolescent girls with hyperandrogenism.

DESIGN

Association study.

SETTING

Academic research environment.

PATIENT(S)

Children referred for the evaluation of premature pubarche (n = 79), adolescent girls with hyperandrogenism (n = 56), and healthy nondiabetic controls (n = 50).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Frequency of the T228A allele in our patients and the relationship of body mass index to presence or absence of the T228A variant in our patient population.

RESULT(S)

Using allele-specific restriction fragment length polymorphism, allele frequencies were found to be similar among the premature pubarche, hyperandrogenism, and control groups (6.0%, 4.6%, and 8.0%, respectively). No statistically significant relationships were found between the SORBS1 genotypes and body mass index or hormone status.

CONCLUSION(S)

This SORBS1 polymorphism does not play a major role in premature pubarche, hyperandrogenism, and/or polycystic ovary syndrome in our patient population.