Nck deficiency is associated with delayed breast carcinoma progression and reduced metastasis

Long noncoding RNA LINC00885 upregulates NCK1 to promote cell viability and migration of triple-negative breast cancer cells through sponging miR-654-3p

BACKGROUND

LINC00885 is a novel oncogenic long noncoding RNA (LncRNA) which is upregulated in various types of cancer, but its function in triple-negative breast cancer (TNBC) remains unknown.

OBJECTIVE

This study aimed to determine the role of LINC00885 on TNBC development.

METHODS

Clinical interrelation and survival analysis were determined using online database. The CCK-8 and Transwell assays were used to detect the proliferation and migration behaviors in TNBC cell lines. The interaction among genes was detected by RNA pull down assay.

RESULTS

LncRNA LINC00885 was highly expressed in TNBC compared to normal breast like. Low levels of LINC00885 was related to good prognosis in TNBC patients compared to TNBC patients with high LINC00885. LINC00885-downregulation inhibited, whereas LINC00885-overexpression promoted the proliferation and migration capability of TNBC cell lines. In TNBC cell lines, noncatalytic region of tyrosine kinase 1 (NCK1) expression was positively associated with LINC00885 expression, and shRNA-mediated the depletion of NCK1 significantly abolished LINC00885 upregulation-mediated pro-tumor effects. Combined with online databases, miR-654-3p was screened as the direct target gene of LINC00885, which could directly bind to 3'-untranslated regions (3'-UTR) of NCK1, resulting in the decreased expression of NCK1 in TNBC cell lines. LINC00885 overexpression-mediated the upregulation of NCK1 was abrogated by miR-654-3p mimics. MiR-654-3p mimics significantly rescued the tumor promotive role caused by LINC00885-overexpression. However, exogenous NCK1 notably eliminated the anti-tumor effects caused by miR-654-3p mimics in LINC00885-overexpressed cells.

CONCLUSIONS

LINC00885 is expressed at a high level in TNBC. LINC00885 promoted proliferation and migration by regulating the miR-654-3p/NCK1 axis in TNBC cell lines. Possibly, LINC00885 can be served as a potential therapeutic target for TNBC.

A Unified Bayesian Framework for Bi-overlapping-Clustering Multi-omics Data via Sparse Matrix Factorization

The advances of modern sequencing techniques have generated an unprecedented amount of multi-omics data which provide great opportunities to quantitatively explore functional genomes from different but complementary perspectives. However, distinct modalities/sequencing technologies generate diverse types of data which greatly complicate statistical modeling because uniquely optimized methods are required for handling each type of data. In this paper, we propose a unified framework for Bayesian nonparametric matrix factorization that infers overlapping bi-clusters for multi-omics data. The proposed method adaptively discretizes different types of observations into common latent states on which cluster structures are built hierarchically. The proposed Bayesian nonparametric method is able to automatically determine the number of clusters. We demonstrate the utility of the proposed method using simulation studies and applications to a single-cell RNA-sequencing dataset, a combination of single-cell RNA-sequencing and single-cell ATAC-sequencing dataset, a bulk RNA-sequencing dataset, and a DNA methylation dataset which reveal several interesting findings that are consistent with biological literature.

Two-Dimensional Polyacrylamide Gel Electrophoresis Coupled with Nanoliquid Chromatography-Tandem Mass Spectrometry-Based Identification of Differentially Expressed Proteins and Tumorigenic Pathways in the MCF7 Breast Cancer Cell Line Transfected for Jumping Translocation Breakpoint Protein Overexpression

The identification of new genes/proteins involved in breast cancer (BC) occurrence is widely used to discover novel biomarkers and understand the molecular mechanisms of BC initiation and progression. The jumping translocation breakpoint (JTB) gene may act both as a tumor suppressor or oncogene in various types of tumors, including BC. Thus, the JTB protein could have the potential to be used as a biomarker in BC, but its neoplastic mechanisms still remain unknown or controversial. We previously analyzed the interacting partners of JTBhigh protein extracted from transfected MCF7 BC cell line using SDS-PAGE complemented with in-solution digestion, respectively. The previous results suggested the JTB contributed to the development of a more aggressive phenotype and behavior for the MCF7 BC cell line through synergistic upregulation of epithelial-mesenchymal transition (EMT), mitotic spindle, and fatty acid metabolism-related pathways. In this work, we aim to complement the previously reported JTB proteomics-based experiments by investigating differentially expressed proteins (DEPs) and tumorigenic pathways associated with JTB overexpression using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Statistically different gel spots were picked for protein digestion, followed by nanoliquid chromatography-tandem mass spectrometry (nLC-MS/MS) analysis. We identified six DEPs related to the JTBhigh condition vs. control that emphasize a pro-tumorigenic (PT) role. Twenty-one proteins, which are known to be usually overexpressed in cancer cells, emphasize an anti-tumorigenic (AT) role when low expression occurs. According to our previous results, proteins that have a PT role are mainly involved in the activation of the EMT process. Interestingly, JTB overexpression has been correlated here with a plethora of significant upregulated and downregulated proteins that sustain JTB tumor suppressive functions. Our present and previous results sustain the necessity of the complementary use of different proteomics-based methods (SDS-PAGE, 2D-PAGE, and in-solution digestion) followed by tandem mass spectrometry to avoid their limitations, with each method leading to the delineation of specific clusters of DEPs that may be merged for a better understanding of molecular pathways and neoplastic mechanisms related to the JTB's role in BC initiation and progression.

Distinct Requirements for Adaptor Proteins NCK1 and NCK2 in Mammary Gland Development

The adaptor proteins NCK1 and NCK2 are well-established signalling nodes that regulate diverse biological processes including cell proliferation and actin dynamics in many tissue types. Here we have investigated the distribution and function of Nck1 and Nck2 in the developing mouse mammary gland. Using publicly available single-cell RNA sequencing data, we uncovered distinct expression profiles between the two paralogs. Nck1 showed widespread expression in luminal, basal, stromal and endothelial cells, while Nck2 was restricted to luminal and basal cells, with prominent enrichment in hormone-sensing luminal subtypes. Next, using mice with global knockout of Nck1 or Nck2, we assessed mammary gland development during and after puberty (5, 8 and 12 weeks of age). Mice lacking Nck1 or Nck2 displayed significant defects in ductal outgrowth and branching at 5 weeks compared to controls, and the defects persisted in Nck2 knockout mice at 8 weeks before normalizing at 12 weeks. These defects were accompanied by an increase in epithelial cell proliferation at 5 weeks and a decrease at 8 weeks in both Nck1 and Nck2 knockout mice. We also profiled expression of several key genes associated with mammary gland development at these timepoints and detected temporal changes in transcript levels of hormone receptors as well as effectors of cell proliferation and migration in Nck1 and Nck2 knockout mice, in line with the distinct phenotypes observed at 5 and 8 weeks. Together these studies reveal a requirement for NCK proteins in mammary gland morphogenesis, and suggest that deregulation of Nck expression could drive breast cancer progression and metastasis.

[Establishment and Preliminary Analysis of Lung Cancer Cell Line A549 with Stable MAP4 K4 Knockdown]

Objective

To analyze the effect of knocking down MAP4 K4 expression on the proliferation and migration of cancer cells, and to explore its underlining molecular mechanisms.

Methods

A stable knockdown MAP4 K4 cell line was constructed and the subcellular localization of the cells was determined with immunofluorescence, cell proliferation assay and cell migration assay. In addition, the effects of down-regulated MAP4 K4 expression were analyzed by examining the difference between the proliferation and migration of cancer cells in the knockdown group and those of the control group.

Results

MAP4 K4 was localized in focal adhesion and cell edges in A549 cells. Stable knockdown of MAP4 K4 expression induced cancer cells to grow in clusters and arrested the progression of the cell cycle and cell migration. Further analysis found that knocking down MAP4 K4 expression in A549 cells induced the accumulation of epithelial cell marker E-cadherin, and subsequently, the down-regulation of N-cadherin, a mesenchymal cell marker, thereby disrupting the "cadherin switch" and the epithelial-mesenchymal conversion. Then, the control group and the knockdown group both received the combined treatment of cisplatin at a final concentration of 5 μmol/L and paclitaxel at a final concentration of 20 nmol/L. The stably knocked down MAP4 K4 expressing cells showed significantly enhanced toxicity of chemotherapeutic drugs to cancer cells.

Conclusion

The study shows that MAP4 K4 regulates the malignant phenotypes of cancer cells and chemoresistance by regulating "cadherin switch" to promote epithelial-mesenchymal transition in A549 cells.

STAT3-induced NCK1 elevation promotes migration of triple-negative breast cancer cells via regulating ERK1/2 signaling

BACKGROUND

Noncatalytic region of tyrosine kinase 1 (NCK1) plays a key role in extracellular matrix degradation, which is required for the metastasis of triple-negative breast cancer (TNBC). However, the role NCK1 plays in the metastatic progression of TNBC is unknown.

METHODS AND RESULTS

Based on online databases, NCK1 was found to be highly expressed in TNBC as compared to normal breast-like subjects, which was also confirmed using TNBC cells and a tissue microarray. NCK1 expression gradually decreased with increased tumor stage. High NCK1 expression displayed a poor prognosis in lymph node-positive metastatic TNBC patients, but not in lymph node-negative patients. Using transwell assays and immunoblotting, we confirmed that NCK1 overexpression promoted, while NCK1 downregulation inhibited migration capabilities, as well as the expression of matrix metalloproteinases (MMP2/9), uridylyl phosphate adenosine, and plasminogen activator inhibitor-1 in TNBC cells. Mechanistically, NCK1 upregulation mediated the activation of MMP2/9 through ERK1/2 activity. Signal transducer and activator of transcription 3 (STAT3) was positively correlated with NCK1. STAT3 could directly bind to the promoter region of NCK1 to promote its expression and was accompanied by the elevation of MMP2/9 and ERK1/2 signaling, which were partially abolished by the knockdown of NCK1 in TNBC cells.

CONCLUSIONS

NCK1 may serve as a diagnostic and prognostic marker of metastatic TNBC. STAT3 upregulation promoted the expression of NCK1, which subsequently induced the migration and activity of MMPs in a ERK1/2 signaling-dependent manner in TNBC cells. NCK1 is a promising target for improving TNBC migration.

Nck adaptors at a glance

The non-catalytic region of tyrosine kinase (Nck) family of adaptors, consisting of Nck1 and Nck2, contributes to selectivity and specificity in the flow of cellular information by recruiting components of signaling networks. Known to play key roles in cytoskeletal remodeling, Nck adaptors modulate host cell-pathogen interactions, immune cell receptor activation, cell adhesion and motility, and intercellular junctions in kidney podocytes. Genetic inactivation of both members of the Nck family results in embryonic lethality; however, viability of mice lacking either one of these adaptors suggests partial functional redundancy. In this Cell Science at a Glance and the accompanying poster, we highlight the molecular organization and functions of the Nck family, focusing on key interactions and pathways, regulation of cellular processes, development, homeostasis and pathogenesis, as well as emerging and non-redundant functions of Nck1 compared to those of Nck2. This article thus aims to provide a timely perspective on the biology of Nck adaptors and their potential as therapeutic targets.

Nck1 promotes the progression of ovarian carcinoma by enhancing the PI3K/AKT/p70S6K signaling

Non-catalytic region of tyrosine kinase adaptor protein 1 (Nck1) is crucial for the progression of cancers. However, little is known on the role of Nck1 in the progression of ovarian carcinoma (OC). Here, we show that Nck1 expression is up-regulated in 176 OC tissues, compared with non-carcinoma ovarian tissues, and the up-regulated Nck1 expression is associated with the aggressiveness of OC and shorter overall and disease-free survival in this population. Higher Nck1 expression was an independent risk factor for poor prognosis of OC. Furthermore, Nck1 silencing by short hairpin RNA (shRNA) technology significantly inhibited the proliferation, migration and invasion of OC cells in vitro and the growth and metastasis of implanted OC tumors in vivo. Human kinase phosphorylation array indicated that Nck1 silencing significantly reduced the relative levels of 11 kinase expression and phosphorylation in OC cells, particularly for decreased levels of p70S6 kinase (p70S6K) and protein kinase B (AKT) expression in SKOV3 cells. Actually, Nck1 silencing significantly decreased PI3K and AKT expression, and reduced AKT and p70S6K phosphorylation while Nck1 over-expression had opposite effects in OC cells. Therefore, our data indicate that Nck1 promotes the progression of OC by enhancing the PI3k/AKT/p70S6K signaling in OC. Our findings suggest that Nck1 expression may be valuable for evaluating the prognosis of OC and as a target for design of new therapies for OC.

Classification models for Invasive Ductal Carcinoma Progression, based on gene expression data-trained supervised machine learning

Early detection of breast cancer and its correct stage determination are important for prognosis and rendering appropriate personalized clinical treatment to breast cancer patients. However, despite considerable efforts and progress, there is a need to identify the specific genomic factors responsible for, or accompanying Invasive Ductal Carcinoma (IDC) progression stages, which can aid the determination of the correct cancer stages. We have developed two-class machine-learning classification models to differentiate the early and late stages of IDC. The prediction models are trained with RNA-seq gene expression profiles representing different IDC stages of 610 patients, obtained from The Cancer Genome Atlas (TCGA). Different supervised learning algorithms were trained and evaluated with an enriched model learning, facilitated by different feature selection methods. We also developed a machine-learning classifier trained on the same datasets with training sets reduced data corresponding to IDC driver genes. Based on these two classifiers, we have developed a web-server Duct-BRCA-CSP to predict early stage from late stages of IDC based on input RNA-seq gene expression profiles. The analysis conducted by us also enables deeper insights into the stage-dependent molecular events accompanying IDC progression. The server is publicly available at http://bioinfo.icgeb.res.in/duct-BRCA-CSP.

Nck adapter proteins promote podosome biogenesis facilitating extracellular matrix degradation and cancer invasion

Background

Podosomes are membrane‐bound adhesive structures formed by actin remodeling. They are capable of extracellular matrix (ECM) degradation, which is a prerequisite for cancer cell invasion and metastasis. The signaling mechanism of podosome formation is still unknown in cancer. We previously reported that Nck adaptors regulate directional cell migration and endothelial lumen formation by actin remodeling, while deficiency of Nck reduces cancer metastasis. This study evaluated the role of Nck adaptors in podosome biogenesis and cancer invasion.

Methods

This study was conducted in vitro using both healthy cells (Human Umbilical Vein Endothelial Cell, 3T3 fibroblasts) and cancer cells (prostate cancer cell line; PC3, breast cancer cell line; MDA‐MB‐231). Confocal and TIRF imaging of cells expressing Green Fluorescence Protein (GFP)  mutant under altered levels of Nck or downstream of kinase 1 (Dok1) was used to evaluate the podosome formation and fluorescent gelatin matrix degradation. Levels of Nck in human breast carcinoma tissue sections were detected by immune histochemistry using Nck polyclonal antibody. Biochemical interaction of Nck/Dok1 was detected in podosome forming cells using immune precipitation and far‐western blotting.

Results

This study demonstrates that ectopic expression of Nck1 and Nck2 can induce the endothelial podosome formation in vitro. Nck silencing by short‐hairpin RNA blocked podosome biogenesis and ECM degradation in cSrc‐Y530F transformed endothelial cells in this study. Immunohistochemical analysis revealed the Nck overexpression in human breast carcinoma tissue sections. Immunoprecipitation and far‐western blotting revealed the biochemical interaction of Nck/p62Dok in podosome forming cells.

Conclusions

Nck adaptors in interaction with Dok1 induce podosome biogenesis and ECM degradation facilitating cancer cell invasion, and therefore a bona fide target of cancer therapy.

Selective recruitment of Nck and Syk contribute to distinct leukocyte immune-type receptor-initiated target interactions

The ability of phagocytes to recognize, immobilize, and engulf extracellular targets are fundamental immune cell processes that allow for the destruction of a variety of microbial intruders. The phagocytic process depends onsignalling events that initiate dynamic changes in the plasma membrane architecture that are required to accommodate the internalization of large particulate targets. To better understand fundamental molecular mechanisms responsible for facilitating phagocytic receptor-mediated regulation of cytoskeletal networks, our research has focused on investigating representative immunoregulatory proteins from the channel catfish (Ictalurus punctatus) leukocyte immune-type receptor family (IpLITRs). Specifically, we have shown that a specific IpLITR-type can regulate the constitutive deployment of filopodial-like structures to actively capture and secure targets to the phagocyte surface, which is followed by F-actin mediated membrane dynamics that are associated with the formation of phagocytic cup-like structures that precede target engulfment. In the present study, we use confocal imaging to examine the recruitment of mediators of the F-actin cytoskeleton during IpLITR-mediated regulation of membrane dynamics. Our results provide novel details regarding the dynamic recruitment of the signaling effectors Nck and Syk during classical as well as atypical IpLITR-induced phagocytic processes.

Revisiting Non-BRCA1/2 Familial Whole Exome Sequencing Datasets Implicates NCK1 as a Cancer Gene

Through linkage and candidate gene screening, many breast cancer (BC) predisposition genes have been identified in the past 20 years. However, the majority of genetic risks that contribute to familial BC remains undetermined. In this study, we revisited whole exome sequencing datasets from non-BRCA1/2 familial BC patients, to search for novel BC predisposition genes. Based on the infinite mutation model, we supposed that rare non-silent variants that cooccurred between familial and TCGA-germline datasets, might play a predisposition contributing role. In our analysis, we not only identified novel potential pathogenic variants from known cancer predisposition genes, such as MRE11, CTR9 but also identified novel candidate predisposition genes, such as NCK1. According to the TCGA mRNA expression dataset of BC, NCK1 was significantly upregulated in basal-like subtypes and downregulated in luminal subtypes. In vitro, NCK1 mutants (D73H and R42Q) transfected MCF7 cell lines, which attributed to the luminal subtype, were much more viable and invasive than the wild type. On the other side, our results also showed that overall survival and disease-free survival of patients with NCK1 variations might be dependent on the genomic context. In conclusion, genetic heterogeneity exists among non-BRCA1/2 BC pedigrees and NCK1 could be a novel BC predisposition gene.

Cathepsin B Is Upregulated and Mediates ECM Degradation in Colon Adenocarcinoma HT29 Cells Overexpressing Snail

During tumor development and ongoing metastasis the acquisition of mesenchymal cell traits by epithelial carcinoma cells is achieved through a programmed phenotypic shift called the epithelial-to-mesenchymal transition, EMT. EMT contributes to increased cancer cell motility and invasiveness mainly through invadosomes, the adhesion structures that accompany the mesenchymal migration. The invadosomes and their associated proteases restrict protease activity to areas of the cell in direct contact with the ECM, thus precisely controlling cell invasion. Our data prove that Snail-overexpressing HT-29 cells that imitate the phenotype of colon cancer cells in the early stage of the EMT showed an increase in the expression and pericellular activity of cathepsin B. It appears that the pericellular localization of cathepsin B, also observed in colon and rectum adenocarcinoma tissue samples, plays a key role in its function.

NCK1 promotes the angiogenesis of cervical squamous carcinoma via Rac1/PAK1/MMP2 signal pathway

OBJECTIVE

The study was to explore the roles of Nck1 in the angiogenesis of cervical squamous cell carcinoma (CSCC).

METHODS

mRNA and protein levels were evaluated with real-time quantitative PCR and immunohistochemisty/western blotting respectively. The cancer microvessel density (MVD) was assayed with CD34 endothelial labeling. Nck1 gene knock-in (SiHa-Nck1+) and knock-down (SiHa-Nck1-) were achieved by gene transfection and siRNA respectively. Protein level from cellular supernatant was measured with ELISA. Proliferation, migration and tube formation of the Human Umbilical Vein Endothelial cells (HUVECs) were evaluated by CCK-8 cell viability assay, transwell chamber assay and in vitro Matrigel tubulation assay respectively.

RESULTS

Nck1 level gradually increased from normal cervical epithelia to high-grade CIN, overexpressed in CSCC and was associated with cancer MVD. The ability of proliferation, migration and tube formation of HUVECs was enhanced in SiHa-Nck1+-treated while decreased in SiHa-NcK1--treated cells compared to SiHa-control-treated cells. Mechanistically, RAC1-GTP, p-PAK1 and MMP2 were increased in SiHa-NCK1+ cells and pretreatment with the Rac1 inhibitor (NSC23766) significantly decreased their levels. Furthermore, inhibition of PAK1 reduced MMP2 level in SiHa-Nck1+ cells whereas the level of Rac1-GTP was unaltered. Also, inhibition of Rac1 or PAK1 impaired angiogenesis-inducing capacity of cancer cells.

CONCLUSIONS

Nck1 promotes the angiogenesis-inducing capacity of CSCC via the Rac1/PAK1/MMP2 signal pathway.

Comparison of breast cancer metastasis models reveals a possible mechanism of tumor aggressiveness

In breast cancer patients, the lungs are among the first sites of cancer metastasis, and in nearly one quarter of metastatic patients, the exclusive first event. Two common mouse models mimic breast cancer lung colonization and distal metastasis: an orthotopic model and intravenous (IV) cell injections. Gene expression analysis of pulmonary lesions from these two methods demonstrated high inter-model resemblance. However, microRNA (miRNA) expression profiles were not compared. In this study, we compared the overall miRNA expression profiles (miRNome) of the orthotopic and IV breast cancer metastasis models and identified significant miRNome changes between the two models. Overexpression of the most significant candidate, miR-96 or downregulation of its validated gene-target, ABCE1 reduced cancer cells 2D/3D cell movement and proliferation in vitro, and abated tumor growth and metastasis formation in vivo. Human data analysis further strengthened miR-96/ABCE1 role in breast cancer tumor aggression. Taken together, our results indicate that IV- and orthotopic models differ by their miRNome. Specifically in our study, breast cancer aggressiveness was dictated by miR-96 regulating ABCE1. Overall, miRNome analysis of various metastatic cancer models may lead to the identification of candidate genes critical to metastasis development.

Nck1 Deficiency Impairs Adipogenesis by Activation of PDGFRα in Preadipocytes

Obesity results from an excessive expansion of white adipose tissue (WAT), which is still poorly understood from an etiologic-mechanistic perspective. Here, we report that Nck1, a Src homology domain-containing adaptor, is upregulated during WAT expansion and in vitro adipogenesis. In agreement, Nck1 mRNA correlates positively with peroxisome proliferator-activated receptor (PPAR) γ and adiponectin mRNAs in the WAT of obese humans, whereas Nck1-deficient mice display smaller WAT depots with reduced number of adipocyte precursors and accumulation of extracellular matrix. Furthermore, silencing Nck1 in 3T3-L1 preadipocytes increases the proliferation and expression of genes encoding collagen, whereas it decreases the expression of adipogenic markers and impairs adipogenesis. Silencing Nck1 in 3T3-L1 preadipocytes also promotes the expression of platelet-derived growth factor (PDGF)-A and platelet-derived growth factor receptor (PDGFR) α activation and signaling. Preventing PDGFRα activation using imatinib, or through PDGF-A or PDGFRα deficiency, inhibits collagen expression in Nck1-deficient preadipocytes. Finally, imatinib rescues differentiation of Nck1-deficient preadipocytes. Altogether, our findings reveal that Nck1 modulates WAT development through PDGFRα-dependent remodeling of preadipocytes.

Vascular Smooth Muscle Contractile Function Declines With Age in Skeletal Muscle Feed Arteries

Aging induces a progressive decline in vasoconstrictor responses in central and peripheral arteries. This study investigated the hypothesis that vascular smooth muscle (VSM) contractile function declines with age in soleus muscle feed arteries (SFA). Contractile function of cannulated SFA isolated from young (4 months) and old (24 months) Fischer 344 rats was assessed by measuring constrictor responses of denuded (endothelium removed) SFA to norepinephrine (NE), phenylephrine (PE), and angiotensin II (Ang II). In addition, we investigated the role of RhoA signaling in modulation of VSM contractile function. Structural and functional characteristics of VSM cells were evaluated by fluorescence imaging and atomic force microscopy (AFM). Results indicated that constrictor responses to PE and Ang II were significantly impaired in old SFA, whereas constrictor responses to NE were preserved. In the presence of a Rho-kinase inhibitor (Y27632), constrictor responses to NE, Ang II, and PE were significantly reduced in young and old SFA. In addition, the age-group difference in constrictor responses to Ang II was eliminated. ROCK1 and ROCK2 content was similar in young and old VSM cells, whereas pROCK1 and pROCK2 were significantly elevated in old VSM cells. Aging was associated with a reduction in smooth muscle α-actin stress fibers and recruitment of proteins to cell-matrix adhesions. Old VSM cells presented an increase in integrin adhesion to the matrix and smooth muscle γ-actin fibers that was associated with increased cell stiffness. In conclusion, our results indicate that VSM contractile function declined with age in SFA. The decrement in contractile function was mediated in part by RhoA/ROCK signaling. Upregulation of pROCK in old VSM cells was not able to rescue contractility in old SFA. Collectively, these results indicate that changes at the VSM cell level play a central role in the reduced contractile function of aged SFA.

Peptide-based sequestration of the adaptor protein Nck1 in pancreatic β cells enhances insulin biogenesis and protects against diabetogenic stresses

One feature of diabetes is the failure of pancreatic β cells to produce insulin, but the molecular mechanisms leading to this failure remain unclear. Increasing evidence supports a role for protein kinase R-like endoplasmic reticulum kinase (PERK) in the development and function of healthy pancreatic β cells. Previously, our group identified the adaptor protein Nck1 as a negative regulator of PERK. Indeed, we demonstrated that Nck1, by directly binding PERK autophosphorylated on Tyr⁵⁶¹, limits PERK activation and signaling. Accordingly, we found that stable depletion of Nck1 in β cells promotes PERK activation and signaling, increases insulin biosynthesis, and improves cell viability in response to diabetes-related stresses. Herein, we explored the therapeutic potential of abrogating the interaction between Nck and PERK to improve β-cell function and survival. To do so, we designed and used a peptide containing the minimal PERK sequence involved in binding Nck1 conjugated to the cell-permeable protein transduction domain from the HIV protein TAT. In the current study, we confirm that the synthetic TAT-Tyr(P)⁵⁶¹ phosphopeptide specifically binds the SH2 domain of Nck and prevents Nck interaction with PERK, thereby promoting basal PERK activation. Moreover, we report that treatment of β cells with TAT-Tyr(P)⁵⁶¹ inhibits glucolipotoxicity-induced apoptosis, whereas it enhances insulin production and secretion. Taken together, our results support the potential of sequestering Nck using a synthetic peptide to enhance basal PERK activation and create more robust β cells.