Journal of Molecular Cell Biology最新文献

Cell migration requires the generation of branched actin networks and recruitment of vesicular membrane that power the protrusion of the plasma membrane in lamellipodia. However, the molecular mechanisms underlying dynamic recruitment of vesicular membrane during cell migration remain elusive. Here, we report a critical mechanism underlying epidermal growth factor (EGF)-elicited Akt signaling-steered cell migration. Using functional proteomics screen, we identified a novel ADP-ribosylation factor 6 (ARF6)-ACAP4 signaling regulator, Acapin, which inhibits the GTPase-activating protein (GAP) activity of ACAP4 to activate ARF6 GTPase in vitro. In cells, EGF stimulation elicits Akt signaling, which recruits Acapin to the lamellipodium membrane via phosphorylation of Acapin at its Ser247 residue and enhances the binding of Acapin to ACAP4 to elevate the ARF6-GTP level. Therefore, Acapin is required for efficiently stimulating cell migration by EGF-Akt signaling. Together, our results demonstrate the role of Acapin in relaying the Akt signaling cascade during cell migration processes.

While gestational diabetes mellitus (GDM) poses great threat to the health of mothers and children, there is no standard early prediction model for this disease yet. This study developed and evaluated a nomogram for predicting GDM in early pregnancy. Overall, 1824 pregnant women were randomly divided into the training and internal validation sets in the ratio of 7:3, with additional 1604 pregnant women for external validation. Multivariate logistic regression analysis was used to develop a prediction model for GDM, and a nomogram was utilized for model visualization. Risk factors in the prediction model involved age, pre-pregnancy body mass index, reproductive history, family history of diabetes, creatinine level, triglyceride level, low-density lipoprotein level, neutrophil count, and monocyte count. Model performance was evaluated using receiver operating characteristic (ROC) curves, calibration curves, and decision clinical analysis (DCA). The area under ROC curve (AUC) value of the model was 0.804 for the training set, and similar AUC values were obtained for the internal (0.800) and external (0.829) validation sets, verifying the stability of the model. The calibration curves showed that the probabilities of GDM predicted by the nomogram highly correlated with the observed frequency values. The DCA curves indicated that the prediction model is clinically useful, thus potentially aiding early pregnancy management in women.

There is an inextricable link between metabolic disorders and autophagy. Gamma-glutamyl hydrolase (GGH) is a lysosomal glycoprotein that reduces intracellular folate stress by catalyzing the hydrolysis of polyglutamylated folate into transportable monoglutamate. The relationship between folate metabolism, involving the folate metabolic enzyme GGH, and autophagy has rarely been reported. In this study, we found that GGH functions as a crucial oncogene in lung adenocarcinomas. Importantly, we found that cell autophagy and autophagic cell death are induced by GGH silencing through the elevated folate stress resulting from folate metabolism and the folate metabolite nicotinamide adenine dinucleotide (NADH). By increasing the NADH/NAD+ ratio, silencing GGH activates adenosine monophosphate-activated protein kinase (AMPK) through the activation of LKB1 and CAMKK2, as well as enhanced AMP/ATP and ADP/ATP ratios, which then triggers the initiation of early autophagy, finally resulting in autophagic cell death. Taken together, our study suggests that GGH may not only serve as a prognostic marker but also play a critical role in the initiation of early autophagy. Interventions targeting GGH to regulate folate metabolism and the proportion of NADH/NAD+ may have translational potential for precision therapy in human cancer.

The activation of hepatic stellate cells (HSCs), characterized by transdifferentiation from a quiescent state to a fibrogenic phenotype, is a core process of liver fibrosis. The metabolic reprogramming of HSCs plays a major role in this process to meet the high energy demands of myofibroblastic HSCs with multiple functions, such as extracellular matrix synthesis, migration, and proliferation. AMP-activated protein kinase (AMPK) is a gatekeeper of intracellular energy homeostasis, but its role in the activation of HSCs and the progression of liver fibrosis remains unclear. Here, we found that the phosphorylation of AMPK in HSCs was upregulated in liver tissues from metabolic dysfunction-associated steatohepatitis patients and from mice treated with carbon tetrachloride (CCl4) or bile duct ligation (BDL). HSC-specific deletion of two catalytic α-subunits of AMPK attenuated liver fibrosis in the CCl4 or BDL mouse model. In vitro analysis demonstrated that AMPK promoted HSC activation when challenged with various profibrogenic stimuli. The activation of AMPKα-deficient HSCs was impaired due to the decreased mitochondrial oxidative phosphorylation but restored after treatment with the mitophagy inducer rapamycin. Mechanistically, both the AMPK-ULK1 and AMPK-Raptor pathways contribute to the maintenance of the mitophagy pathway and mitochondrial quality. These findings provide direct evidence of the crucial role of AMPK-mitophagy signaling in ensuring mitochondrial health and sufficient energy supply during HSC activation. In this study, AMPK was modulated in HSCs prior to activation, which is distinguished from previous investigations and thus provides new insights into the role of AMPK during distinct phases of HSC activation.

The Wnt signaling pathway plays important roles in cardiomyocyte proliferation and cardiac regeneration after heart injury. Abnormal activation of the Wnt pathway causes a reduction in cardiomyocyte function, leading to hypertrophy, fibrosis, and heart failure. However, the mechanism through which Wnt signaling affects cardiomyocyte function during cardiac diseases is still unclear. In this study, we observed that activation of the Wnt/β-catenin pathway, but not the Wnt/Ca2+ pathway, leads to significant cytosol calcium enrichment. Such an effect can be inhibited by cycloheximide that blocks the downstream gene expression. By analyzing the transcriptome data, we found that activation of the Wnt/β-catenin pathway significantly upregulates the expression level of muscle-selective A kinase anchoring protein (mAKAP, also called AKAP6), a scaffold protein that can improve the interaction between protein kinase A (PKA) and its substrate ryanodine receptor 2 (RyR2) in cardiomyocytes. We further identified that AKAP6 is a target gene of the canonical Wnt pathway and increasing AKAP6 expression can enhance RyR2 phosphorylation by PKA, causing the sarcoplasmic reticulum calcium leakage and finally heart dysfunction. Our finding that the Wnt/β-catenin pathway affects cardiac calcium regulation via AKAP6 and RyR2 provides profound insights into heart diseases and sheds light on potential therapeutic strategies.

The development and homeostasis of intestinal epithelium are mediated by actively proliferating Lgr5+ stem cells, which possess a remarkable self-renewal and differentiation capacity. Recently, our study demonstrated that N6-methyladenosine (m6A) methylation was essential for the survival of colonic stem cells. Here, we show that methyltransferase-like 3 (METTL3) expression is downregulated in the colon mucosa in ulcerative colitis (UC) patients and strongly associated with the differentiation and maturation of goblet cells during inflammation. In mice, depletion of Mettl3 significantly inhibits the self-renewal and differentiation of Lgr5+ stem cells, especially the differentiation and maturation of goblet cells, resulting in intestinal dysplasia and spontaneous inflammation. Mechanistically, Mettl3 deletion-mediated m6A loss facilitates the expression levels of growth factor receptor binding protein 10 (Grb10) and interferon-related developmental regulator 1 (Ifrd1) via increasing their messenger RNA stability. We further demonstrate that the levels of GRB10 and IFRD1 are negatively correlated with METTL3 level in UC samples. Collectively, our data indicate that METTL3 enhances the self-renewal and differentiation of Lgr5+ stem cells during intestinal development and inflammation, and thus it may be a potential therapeutic target for UC treatment.

Calciphylaxis is a rare, progressive disorder characterized by subcutaneous adipose and dermal microvascular calcifications, microthrombi, and endothelial damage. It mainly affects patients with chronic kidney disease (CKD), which is also known as calcific uremic arteriolopathy. Skin biopsy is the gold standard for diagnosis, but it is an invasive procedure. Calciphylaxis frequently results in ischemic and nonhealing ulcerations with a high mortality rate. A multidisciplinary targeted approach is the primary treatment method. Vascular calcification, which is a common complication in patients with CKD, cannot completely explain the rapid progression of calciphylaxis. This article reviews the advances in the epidemiological characteristics, risk factors, and diagnosis, including non-uremic calciphylaxis and visceral calciphylaxis, pathogenesis, associated animal models, and treatment of calciphylaxis. The scarcity of animal models that mimic the clinical presentation of calciphylaxis hampers the understanding of its pathogenesis. The acute effects on progressive vascular injury, including the induction of severe ischemia and inflammatory responses, have been emphasized. Actively listening to the voices of patients and their families and building a multidimensional research system with artificial intelligence technologies based on the specific molecular makeup of calciphylaxis patients will help tailor regenerative treatment strategies. Mesenchymal stem cells (MSCs) may represent a novel therapy for calciphylaxis because of their regenerative effects, inhibition of vascular calcification, anti-infection and immunomodulation properties, and improvement of hypercoagulability. Safe, effective, accessible, and economical MSC strategies guided by biomarkers deserve consideration for the treatment of this devastating disease.