Multitasking: Dual Leucine Zipper-Bearing Kinases in Neuronal Development and Stress Management.

The dual leucine zipper-bearing kinase (DLK) and leucine zipper-bearing kinase (LZK) are evolutionarily conserved MAPKKKs of the mixed-lineage kinase family. Acting upstream of stress-responsive JNK and p38 MAP kinases, DLK and LZK have emerged as central players in neuronal responses to a variety of acute and traumatic injuries. Recent studies also implicate their function in astrocytes, microglia, and other nonneuronal cells, reflecting their expanding roles in the multicellular response to injury and in disease. Of particular note is the potential link of these kinases to neurodegenerative diseases and cancer. It is thus critical to understand the physiological contexts under which these kinases are activated, as well as the signal transduction mechanisms that mediate specific functional outcomes. In this review we first provide a historical overview of the biochemical and functional dissection of these kinases. We then discuss recent findings on regulating their activity to enhance cellular protection following injury and in disease, focusing on but not limited to the nervous system.

m6A mRNA methylation by METTL14 regulates early pancreatic cell differentiation.

N6-methyladenosine (m6A) is the most abundant chemical modification in mRNA and plays important roles in human and mouse embryonic stem cell pluripotency, maintenance, and differentiation. We have recently reported that m6A is involved in the postnatal control of ß-cell function in physiological states and in type 1 and 2 diabetes. However, the precise mechanisms by which m6A acts to regulate the development of human and mouse pancreas are unexplored. Here, we show that the m6A landscape is dynamic during human pancreas development, and that METTL14, one of the m6A writer complex proteins, is essential for the early differentiation of both human and mouse pancreatic cells.

DMPPred: a tool for identification of antigenic regions responsible for inducing type 1 diabetes mellitus.

There are a number of antigens that induce autoimmune response against ß-cells, leading to type 1 diabetes mellitus (T1DM). Recently, several antigen-specific immunotherapies have been developed to treat T1DM. Thus, identification of T1DM associated peptides with antigenic regions or epitopes is important for peptide based-therapeutics (e.g. immunotherapeutic). In this study, for the first time, an attempt has been made to develop a method for predicting, designing, and scanning of T1DM associated peptides with high precision. We analysed 815 T1DM associated peptides and observed that these peptides are not associated with a specific class of HLA alleles. Thus, HLA binder prediction methods are not suitable for predicting T1DM associated peptides. First, we developed a similarity/alignment based method using Basic Local Alignment Search Tool and achieved a high probability of correct hits with poor coverage. Second, we developed an alignment-free method using machine learning techniques and got a maximum AUROC of 0.89 using dipeptide composition. Finally, we developed a hybrid method that combines the strength of both alignment free and alignment-based methods and achieves maximum area under the receiver operating characteristic of 0.95 with Matthew's correlation coefficient of 0.81 on an independent dataset. We developed a web server 'DMPPred' and stand-alone server for predicting, designing and scanning T1DM associated peptides (https://webs.iiitd.edu.in/raghava/dmppred/).

Hypoxia causes pancreatic ß-cell dysfunction and impairs insulin secretion by activating the transcriptional repressor BHLHE40.

Hypoxia can occur in pancreatic ß-cells in type 2 diabetes. Although hypoxia exerts deleterious effects on ß-cell function, the associated mechanisms are largely unknown. Here, we show that the transcriptional repressor basic helix-loop-helix family member e40 (BHLHE40) is highly induced in hypoxic mouse and human ß-cells and suppresses insulin secretion. Conversely, BHLHE40 deficiency in hypoxic MIN6 cells or ß-cells of ob/ob mice reverses defects in insulin secretion. Mechanistically, BHLHE40 represses the expression of Mafa, encoding the transcription factor musculoaponeurotic fibrosarcoma oncogene family A (MAFA), by attenuating the binding of pancreas/duodenum homeobox protein 1 (PDX1) to its enhancer region. Impaired insulin secretion in hypoxic ß-cells was recovered by MAFA re-expression. Collectively, our work identifies BHLHE40 as a key hypoxia-induced transcriptional repressor in ß-cells that inhibit insulin secretion by suppressing MAFA expression.

Monitoring glycolytic dynamics in single cells using a fluorescent biosensor for fructose 1,6-bisphosphate.

Cellular metabolism is regulated over space and time to ensure that energy production is efficiently matched with consumption. Fluorescent biosensors are useful tools for studying metabolism as they enable real-time detection of metabolite abundance with single-cell resolution. For monitoring glycolysis, the intermediate fructose 1,6-bisphosphate (FBP) is a particularly informative signal as its concentration is strongly correlated with flux through the whole pathway. Using GFP insertion into the ligand-binding domain of the Bacillus subtilis transcriptional regulator CggR, we developed a fluorescent biosensor for FBP termed HYlight. We demonstrate that HYlight can reliably report the real-time dynamics of glycolysis in living cells and tissues, driven by various metabolic or pharmacological perturbations, alone or in combination with other physiologically relevant signals. Using this sensor, we uncovered previously unknown aspects of ß-cell glycolytic heterogeneity and dynamics.

A distinct role of STING in regulating glucose homeostasis through insulin sensitivity and insulin secretion.

Insulin resistance and ß-cell dysfunction are two main molecular bases yet to be further elucidated for type 2 diabetes (T2D). Accumulating evidence indicates that stimulator of interferon genes (STING) plays an important role in regulating insulin sensitivity. However, its function in ß-cells remains unknown. Herein, using global STING knockout (STING-/-) and ß-cell-specific STING knockout (STING-ßKO) mouse models, we revealed a distinct role of STING in the regulation of glucose homeostasis through peripheral tissues and ß-cells. Specially, although STING-/- beneficially alleviated insulin resistance and glucose intolerance induced by high-fat diet, it surprisingly impaired islet glucose-stimulated insulin secretion (GSIS). Importantly, STING is decreased in islets of db/db mice and patients with T2D, suggesting a possible role of STING in ß-cell dysfunction. Indeed, STING-ßKO caused glucose intolerance due to impaired GSIS, indicating that STING is required for normal ß-cell function. Islet transcriptome analysis showed that STING deficiency decreased expression of ß-cell function-related genes, including Glut2, Kcnj11, and Abcc8, contributing to impaired GSIS. Mechanistically, the assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) and cleavage under targets and tagmentation (CUT&Tag) analyses suggested that Pax6 was the transcription factor that might be associated with defective GSIS in STING-ßKO mice. Indeed, Pax6 messenger RNA and protein levels were down-regulated and its nuclear localization was lost in STING-ßKO ß-cells. Together, these data revealed a function of STING in the regulation of insulin secretion and established pathophysiological significance of fine-tuned STING within ß-cells and insulin target tissues for maintaining glucose homeostasis.

Targeting ß-Cell Plasticity: A Promising Approach for Diabetes Treatment.

The ß-cells within the pancreas play a pivotal role in insulin production and secretion, responding to fluctuations in blood glucose levels. However, factors like obesity, dietary habits, and prolonged insulin resistance can compromise ß-cell function, contributing to the development of Type 2 Diabetes (T2D). A critical aspect of this dysfunction involves ß-cell dedifferentiation and transdifferentiation, wherein these cells lose their specialized characteristics and adopt different identities, notably transitioning towards progenitor or other pancreatic cell types like α-cells. This process significantly contributes to ß-cell malfunction and the progression of T2D, often surpassing the impact of outright ß-cell loss. Alterations in the expressions of specific genes and transcription factors unique to ß-cells, along with epigenetic modifications and environmental factors such as inflammation, oxidative stress, and mitochondrial dysfunction, underpin the occurrence of ß-cell dedifferentiation and the onset of T2D. Recent research underscores the potential therapeutic value for targeting ß-cell dedifferentiation to manage T2D effectively. In this review, we aim to dissect the intricate mechanisms governing ß-cell dedifferentiation and explore the therapeutic avenues stemming from these insights.

Fluorinated curcumin derivative (Shiga-Y6) modulates the level of thioredoxin-interacting protein (TXNIP) in a mouse model of diabetes.

Thioredoxin interacting protein (TXNIP) has emerged as a significant regulator of ß-cell mass and loss, rendering it an attractive target for treating diabetes. We previously showed that Shiga-Y6, a fluorinated curcumin derivative, inhibited TXNIP mRNA and protein expression in vitro, raising the question of whether the same effect could be translated in vivo. Herein, we examined the effect of Shiga-Y6 on TNXIP levels and explored its therapeutic potential in a mouse model of diabetes, Akita mice. We intraperitoneally injected Shiga-Y6 (SY6; 30 mg/kg of body weight) or vehicle into 8-week-old Akita mice for 28 consecutive days. On day 29, the mice were euthanized, following which the serum levels of glucose, insulin, and glucagon were measured using ELISA, the expression of TXNIP in pancreatic tissue lysates was determined using western blotting, and the level of ß-cell apoptosis was assessed using the TUNEL assay. TXNIP levels in the pancreatic tissue of Akita mice were significantly elevated compared with wild-type (WT) mice. Shiga-Y6 administration for 28 days significantly lowered those levels compared with Akita mice that received vehicle to a level comparable to WT mice. In immunohistochemical analysis, both α- to ß-cell ratio and the number of apoptotic ß-cells were significantly reduced in SY6-treated Akita mice, compared with vehicle-treated Akita mice. Findings from the present study suggest a potential of Shiga-Y6 as an antidiabetic agent through lowering TXNIP protein levels and ameliorating pancreatic ß-cells apoptosis.

Glycolytic enzyme Enolase-1 regulates insulin gene expression in pancreatic ß-cell.

Enolase-1 (Eno1) plays a critical role in regulating glucose metabolism; however, its specific impact on pancreatic islet ß-cells remains elusive. This study aimed to provide a preliminary exploration of Eno1 function in pancreatic islet ß-cells. The findings revealed that the expression of ENO1 mRNA in type 2 diabetes donors was significantly increased and positively correlated with HbA1C and negatively correlated with insulin gene expression. A high level of Eno1 in human insulin-secreting rat INS-1832/13 cells with co-localization with intracellular insulin proteins was accordingly observed. Silencing of Eno1 using siRNA or inhibiting Eno1 protein activity with an Eno1 antagonist significantly reduced insulin secretion and insulin content in ß-cells, while the proinsulin/insulin content ratio remained unchanged. This reduction in ß-cells function was accompanied by a notable decrease in intracellular ATP and mitochondrial cytochrome C levels. Overall, our findings confirm that Eno1 regulates the insulin secretion process, particularly glucose metabolism and ATP production in the ß-cells. The mechanism primarily involves its influence on insulin production, suggesting that Eno1 represents a potential target for ß-cell protection and diabetes treatment.

Vitamin D supplementation could enhance the effectiveness of glibenclamide in treating type 2 diabetes by improving the function of pancreatic ß-cells through the NF-κB pathway.

PURPOSE: The high morbidity and mortality associated with type 2 diabetes mellitus (T2DM) pose a significant global health challenge, necessitating the development of more efficient anti-diabetic drugs with fewer side effects. This study investigated the intervention of vitamin D3 combined with glibenclamide in rats with T2DM to elucidate its effects on pancreatic ß-cells through the NF-κB pathway. METHODS: Twenty-four healthy male Sprague-Dawley (SD) rats were randomly assigned to four groups: the control group (CG), the model group (MG), the glibenclamide group (GG), and the glibenclamide + vitamin D3 group (GDG). After inducing the T2DM model using high-fat and high-sugar diet and intraperitoneal injection of streptozotocin, the rats in the GG group were administered glibenclamide orally (0.6 mg/kg/day), while those in the GDG group received both glibenclamide (0.6 mg/kg/day) and vitamin D3 (500 IU/kg/day) in corn oil for a duration of 8 weeks. Biochemical indices were measured, and histopathological changes in pancreatic tissue and islet ß cells were observed using hematoxylin and eosin staining. The expression of pancreatic nuclear factor κB (NF-κB), islet ß-cells, and inflammatory cytokines were assessed using the TUNEL method and PCR. RESULTS: According to the data from this current study, the GDG group showed significant positive differences in plasma biochemical indices, as well as in the expression of ß cells, NF-κB p65, TNF-α, IL-1ß, INF-γ, and Fas, compared to the GG and CG groups (P < 0.05). CONCLUSION: The results suggest that vitamin D has beneficial effects on T2DM by improving the functions of islet ß cells through inhibition of the NF-κB signaling pathway. Therefore, it is suggested that vitamin D supplementation, when used alongside antidiabetic drugs, may more effectively prevent and treat T2DM.

A developmental lineage-based gene co-expression network for mouse pancreatic ß-cells reveals a role for Zfp800 in pancreas development.

To gain a deeper understanding of pancreatic ß-cell development, we used iterative weighted gene correlation network analysis to calculate a gene co-expression network (GCN) from 11 temporally and genetically defined murine cell populations. The GCN, which contained 91 distinct modules, was then used to gain three new biological insights. First, we found that the clustered protocadherin genes are differentially expressed during pancreas development. Pcdhγ genes are preferentially expressed in pancreatic endoderm, Pcdhß genes in nascent islets, and Pcdhα genes in mature ß-cells. Second, after extracting sub-networks of transcriptional regulators for each developmental stage, we identified 81 zinc finger protein (ZFP) genes that are preferentially expressed during endocrine specification and ß-cell maturation. Third, we used the GCN to select three ZFPs for further analysis by CRISPR mutagenesis of mice. Zfp800 null mice exhibited early postnatal lethality, and at E18.5 their pancreata exhibited a reduced number of pancreatic endocrine cells, alterations in exocrine cell morphology, and marked changes in expression of genes involved in protein translation, hormone secretion and developmental pathways in the pancreas. Together, our results suggest that developmentally oriented GCNs have utility for gaining new insights into gene regulation during organogenesis.

Glucotoxicity is mediated by cytoplasmic distribution of RAP1 in pancreatic ß-cells.

Diabetes mellitus (DM) is a group of chronic metabolic disorders characterized by persistent hyperglycemia. In our study, we analyzed the level and location of RAP1 changes in the development of ß-cell dysfunction induced by glucotoxicity. We employed three pancreatic ß-cell lines, namely INS-1, 1.2B4, and NIT-1, as well as a streptozotocin-induced diabetes rat model. We demonstrate that after high glucose treatment, RAP1 is increased, probably through induction by AKT, allowing RAP1 to shuttle from the nucleus to the cytoplasm and activate NF-κB signaling. Furthermore, non-enzymatic post-translational modifications of RAP1, such as advanced glycation end products and carbonylation may affect the function of RAP1, such as activation of the NF-κB signaling. Taken together, we showed that RAP1 is a new player in the mechanism of glucotoxicity in pancreatic ß-cells.

From stem cells to pancreatic ß-cells: strategies, applications, and potential treatments for diabetes.

Loss and functional failure of pancreatic ß-cells results in disruption of glucose homeostasis and progression of diabetes. Although whole pancreas or pancreatic islet transplantation serves as a promising approach for ß-cell replenishment and diabetes therapy, the severe scarcity of donor islets makes it unattainable for most diabetic patients. Stem cells, particularly induced pluripotent stem cells (iPSCs), are promising for the treatment of diabetes owing to their self-renewal capacity and ability to differentiate into functional ß-cells. In this review, we first introduce the development of functional ß-cells and their heterogeneity and then turn to highlight recent advances in the generation of ß-cells from stem cells and their potential applications in disease modeling, drug discovery and clinical therapy. Finally, we have discussed the current challenges in developing stem cell-based therapeutic strategies for improving the treatment of diabetes. Although some significant technical hurdles remain, stem cells offer great hope for patients with diabetes and will certainly transform future clinical practice.

Insufficient compensatory pancreatic ß-cells function might be closely associated with hyperuricemia in U.S. adults: evidence from the National Health and Nutrition Examination Survey.

BACKGROUND: The prevalence of hyperuricemia (HUA) is gradually increasing worldwide. HUA is closely related to diabetes, but the relationship between HUA and pancreatic ß-cells function in the population is unclear. The purpose of this article is to investigate the association between pancreatic ß-cells and HUA. METHODS: This cross-sectional study examined the association between pancreatic ß-cells and HUA in 1999-2004 using data from the National Health and Nutrition Examination Survey (NHANES). Subjects were divided into two groups: HUA and non-HUA. Pancreatic ß-cells function levels were assessed using homeostasis model assessment version 2-%S (HOMA2-%S), homeostasis model assessment version 2-%B (HOMA2-%B) and disposition index (DI). Multivariate logistic regression models and restricted cubic spline models were fitted to assess the association of pancreatic ß-cells function with HUA. RESULTS: The final analysis included 5496 subjects with a mean age of 46.3 years (standard error (SE), 0.4). The weighted means of HOMA2-%B, HOMA2-%S and DI were 118.1 (SE, 1.0), 69.9(SE, 1.1) and 73.9 (SE, 0.7), respectively. After adjustment for major confounders, participants in the highest quartile of HOMA2-%B had a higher risk of HUA (OR = 2.55, 95% CI: 1.89-3.43) compared to participants in the lowest quartile. In contrast, participants in the lowest quartile of HOMA2-%S were significantly more likely to have HUA than that in the highest quartile (OR = 3.87, 95% CI: 2.74-5.45), and similar results were observed in DI (OR = 1.98, 95% CI: 1.32-2.97). Multivariate adjusted restricted cubic spline analysis found evidence of non-linear associations between HOMA2-%B, HOAM2-%S, DI and the prevalence of HUA. CONCLUSION: Our finding illustrated the indicators of inadequate ß-cells compensation might be a new predictor for the presence of HUA in U.S. adults, highlighting a critical role of pancreatic ß-cells function on HUA.

An Insight into Vital Genes Responsible for ß-cell Formation.

The regulation of glucose homeostasis and insulin secretion by pancreatic ß-cells, when disturbed, will result in diabetes mellitus. Replacement of dysfunctional or lost ß-cells with fully functional ones can tackle the problem of ß-cell generation in diabetes mellitus. Various pancreatic-specific genes are expressed during different stages of development, which have essential roles in pancreatogenesis and ß-cell formation. These factors play a critical role in cellular-based studies like transdifferentiation or de-differentiation of somatic cells to multipotent or pluripotent stem cells and their differentiation into functional ß-cells. This work gives an overview of crucial transcription factors expressed during various stages of pancreas development and their role in ß-cell specification. In addition, it also provides a perspective on the underlying molecular mechanisms.

miR-10a/b-5p-NCOR2 Regulates Insulin-Resistant Diabetes in Female Mice.

Gender and biological sex have distinct impacts on the pathogenesis of type 2 diabetes (T2D). Estrogen deficiency is known to predispose female mice to T2D. In our previous study, we found that a high-fat, high-sucrose diet (HFHSD) induces T2D in male mice through the miR-10b-5p/KLF11/KIT pathway, but not in females, highlighting hormonal disparities in T2D susceptibility. However, the underlying molecular mechanisms of this hormonal protection in females remain elusive. To address this knowledge gap, we utilized ovariectomized, estrogen-deficient female mice, fed them a HFHSD to induce T2D, and investigated the molecular mechanisms involved in estrogen-deficient diabetic female mice, relevant cell lines, and female T2D patients. Initially, female mice fed a HFHSD exhibited a delayed onset of T2D, but ovariectomy-induced estrogen deficiency promptly precipitated T2D without delay. Intriguingly, insulin (INS) was upregulated, while insulin receptor (INSR) and protein kinase B (AKT) were downregulated in these estrogen-deficient diabetic female mice, indicating insulin-resistant T2D. These dysregulations of INS, INSR, and AKT were mediated by a miR-10a/b-5p-NCOR2 axis. Treatment with miR-10a/b-5p effectively alleviated hyperglycemia in estrogen-deficient T2D female mice, while ß-estradiol temporarily reduced hyperglycemia. Consistent with the murine findings, plasma samples from female T2D patients exhibited significant reductions in miR-10a/b-5p, estrogen, and INSR, but increased insulin levels. Our findings suggest that estrogen protects against insulin-resistant T2D in females through miR-10a/b-5p/NCOR2 pathway, indicating the potential therapeutic benefits of miR-10a/b-5p restoration in female T2D management.

Roles of ß-Cell Hypoxia in the Progression of Type 2 Diabetes.

Type 2 diabetes is a chronic disease marked by hyperglycemia; impaired insulin secretion by pancreatic ß-cells is a hallmark of this disease. Recent studies have shown that hypoxia occurs in the ß-cells of patients with type 2 diabetes and hypoxia, in turn, contributes to the insulin secretion defect and ß-cell loss through various mechanisms, including the activation of hypoxia-inducible factors, induction of transcriptional repressors, and activation of AMP-activated protein kinase. This review focuses on advances in our understanding of the contribution of ß-cell hypoxia to the development of ß-cell dysfunction in type 2 diabetes. A better understanding of ß-cell hypoxia might be useful in the development of new strategies for treating type 2 diabetes.

Chronic Epinephrine-Induced Endoplasmic Reticulum and Oxidative Stress Impairs Pancreatic ß-Cells Function and Fate.

Epinephrine influences the function of pancreatic ß-cells, primarily through the α2A-adrenergic receptor (α2A-AR) on their plasma membrane. Previous studies indicate that epinephrine transiently suppresses insulin secretion, whereas prolonged exposure induces its compensatory secretion. Nonetheless, the impact of epinephrine-induced α2A-AR signaling on the survival and function of pancreatic ß-cells, particularly the impact of reprogramming after their removal from sustained epinephrine stimulation, remains elusive. In the present study, we applied MIN6, a murine insulinoma cell line, with 3 days of high concentration epinephrine incubation and 2 days of standard incubation, explored cell function and activity, and analyzed relevant regulatory pathways. The results showed that chronic epinephrine incubation led to the desensitization of α2A-AR and enhanced insulin secretion. An increased number of docked insulin granules and impaired Syntaxin-2 was found after chronic epinephrine exposure. Growth curve and cell cycle analyses showed the inhibition of cell proliferation. Transcriptome analysis showed the occurrence of endoplasmic reticulum stress (ER stress) and oxidative stress, such as the presence of BiP, CHOP, IRE1, ATF4, and XBP, affecting cellular endoplasmic reticulum function and survival, along with UCP2, OPA1, PINK, and PRKN, associated with mitochondrial dysfunction. Consequently, we conclude that chronic exposure to epinephrine induces α2A-AR desensitization and leads to ER and oxidative stress, impairing protein processing and mitochondrial function, leading to modified pancreatic ß-cell secretory function and cell fate.

Antidiabetic Potential of Abelmoschus manihot Flower Extract: In Vitro and Intracellular Studies.

Abelmoschus manihot (L.) Medic flower (AMf) exhibits both nutritional value and bioactivities such as antioxidative, anti-inflammatory, neuroprotective, cardioprotective, and hepatoprotective effects. The aim of this investigation was to examine the potential impact of three different solvent extracts of AMf: supercritical CO2 extraction extract, water extract, and ethanol extract (AME), on management of diabetes. All three extracts demonstrated significant inhibitory effects on α-glucosidase (IC50 = 157-261 µg/mL) and lipase (IC50 = 401-577 µg/mL) activities while enhancing the α-amylase activity (32.4-41.8 folds at 200 µg/mL). Moreover, all three extracts exhibited notable inhibition of the formation of advanced glycation end-products, including the Amadori products (inhibition rates = 15.7-36.6%) and the dicarbonyl compounds (inhibition rates = 18.6-28.3%). Among the three extracts, AME exhibited the most pronounced inhibitory effect. AME displayed substantial in vitro and intracellular antioxidative activity, and effectively reduced ROS production (135% at 500 µg/mL) in ß-cells under hyperglycemic (HG) conditions. AME also enhanced the activity and gene expression of antioxidant enzymes, which were markedly decreased in the HG-induced ß-cells. Furthermore, AME protected ß-cell viability and maintained normal insulin secretion under HG conditions, likely due to its ability to reduce oxidative stress within ß-cells. This study demonstrated the potential of AME in preventing and managing diabetes and its associated complications. Further in vivo research is necessary to thoroughly elucidate the preventive effects and their underlying mechanisms.

ß-Cells retain a pool of insulin-containing secretory vesicles regulated by adherens junctions and the cadherin-binding protein p120 catenin.

The ß-cells of the islets of Langerhans are the sole producers of insulin in the human body. In response to rising glucose levels, insulin-containing vesicles inside ß-cells fuse with the plasma membrane and release their cargo. However, the mechanisms regulating this process are only partly understood. Previous evidence indicated reductions in α-catenin elevate insulin release, while reductions in ß-catenin decrease insulin release. α- and ß-catenin contribute to cellular regulation in a range of ways but one is as members of the adherens junction complex. Therefore, we investigated the effects of adherens junctions on insulin release. We show in INS-1E ß-cells knockdown of either E- or N-cadherin had only small effects on insulin secretion, but simultaneous knockdown of both cadherins resulted in a significant increase in basal insulin release to the same level as glucose-stimulated release. This double knockdown also significantly attenuated levels of p120 catenin, a cadherin-binding partner involved in regulating cadherin turnover. Conversely, reducing p120 catenin levels with siRNA destabilized both E- and N-cadherin, and this was also associated with an increase in levels of insulin secreted from INS-1E cells. Furthermore, there were also changes in these cells consistent with higher insulin release, namely reductions in levels of F-actin and increased intracellular free Ca2+ levels in response to KCl-induced membrane depolarization. Taken together, these data provide evidence that adherens junctions play important roles in retaining a pool of insulin secretory vesicles within the cell and establish a role for p120 catenin in regulating this process.