Charlie Norwood VA Medical Center

About: Charlie Norwood VA Medical Center is a healthcare organization based out in Augusta, Georgia, United States. It is known for research contribution in the topics: Autophagy & Kidney. The organization has 349 authors who have published 490 publications receiving 16360 citations. The organization is also known as: Augusta VA Medical Center.

FOXO1-Mediated Downregulation of RAB27B Leads to Decreased Exosome Secretion in Diabetic Kidneys

Abstract: Exosomes have been implicated in diabetic kidney disease (DKD), but the regulation of exosomes in DKD is largely unknown. Here, we have verified the decrease of exosome secretion in DKD and unveiled the underlying mechanism. In Boston University mouse proximal tubule (BUMPT) cells, high-glucose (HG) treatment led to a significant decrease in exosome secretion, which was associated with specific downregulation of RAB27B, a key guanosine-5'-triphosphatase in exosome secretion. Overexpression of RAB27B restored exosome secretion in HG-treated cells, suggesting a role of RAB27B downregulation in the decrease of exosome secretion in DKD. To understand the mechanism of RAB27B downregulation, we conducted bioinformatics analysis that identified FOXO1 binding sites in the Rab27b gene promoter. Consistently, HG induced phosphorylation of FOXO1 in BUMPT cells, preventing FOXO1 accumulation and activation in the nucleus. Overexpression of nonphosphorylatable, constitutively active FOXO1 led to the upregulation of RAB27B and an increase in exosome secretion in HG-treated cells. In vivo, compared with normal mice, diabetic mice showed increased FOXO1 phosphorylation, decreased RAB27B expression, and reduced exosome secretion. Collectively, these results unveil the mechanism of exosome dysfunction in DKD where FOXO1 is phosphorylated and inactivated in DKD, resulting in RAB27B downregulation and the decrease of exosome secretion.

Agrin to YAP in Cancer and Neuromuscular Junctions

Abstract: Agrin is utilized by motor neurons to stimulate the LRP4-MuSK receptor in muscles for neuromuscular junction (NMJ) formation. Recent studies of cancer have identified novel functions of the low-density lipoprotein receptor-related protein 4-muscle-specific kinase (LRP4-MuSK) pathway. Agrin may act as a mechanotransduction signal in the extracellular matrix (ECM) to coordinate the cross-talk between the LRP4-MuSK pathway and integrin-focal adhesion pathway. Ensuing Yes-associated protein (YAP) activation promotes hepatocellular carcinoma (HCC). Here, we discuss the implications of the converged pathways in NMJ formation and liver cancer.