Renal proximal tubular damage and repair are hallmarks of acute kidney injury. Because glycogen synthase kinase-3β (GSK-3β) is an important cellular regulator of survival and proliferation, we determined its role during injury and recovery of proximal tubules in a mercuric chloride-induced nephrotoxic model of acute kidney injury. Renal proximal tubule-specific GSK-3β knockout mice exposed to mercuric chloride had improved survival and renal function compared to wild type mice. Apoptosis, measured by TUNEL staining, Bax activation, and caspase 3 cleavage were all reduced in the knockout mice. The restoration of renal structure, function, and cell proliferation was also accelerated in the GSK-3β knockout mice. This enhanced repair, evidenced by increased Ki-67 and BrdU staining, along with increased cyclin D1 and c-myc levels, was recapitulated by treatment of wild type mice with the small-molecule GSK-3 inhibitor TDZD-8 following injury. This confirmed that hastened repair in the knockout mice was not merely due to lower initial injury levels. Thus, inhibition of GSK-3β prior to nephrotoxic insult protects from renal injury. Such treatment after acute kidney injury may accelerate repair and regeneration.

Glycogen synthase kinase-3β (GSK3β) is a serine/threonine protein kinase that plays an important role in renal tubular injury and regeneration in acute kidney injury. However, its role in the development of renal fibrosis, often a long-term consequence of acute kidney injury, is unknown. Using a mouse model of renal fibrosis induced by ischemia-reperfusion injury, we demonstrate increased GSK3β expression and activity in fibrotic kidneys, and its presence in myofibroblasts in addition to tubular epithelial cells. Pharmacological inhibition of GSK3 using TDZD-8 starting before or after ischemia-reperfusion significantly suppressed renal fibrosis by reducing the myofibroblast population, collagen-1 and fibronectin deposition, inflammatory cytokines, and macrophage infiltration. GSK3 inhibition in vivo reduced TGF-β1, SMAD3 activation and plasminogen activator inhibitor-1 levels. Consistently in vitro, TGF-β1 treatment increased GSK3β expression and GSK3 inhibition abolished TGF-β1-induced SMAD3 activation and α-smooth muscle actin (α-SMA) expression in cultured renal fibroblasts. Importantly, overexpression of constitutively active GSK3β stimulated α-SMA expression even in the absence of TGF-β1 treatment. These results suggest that TGF-β regulates GSK3β, which in turn is important for TGF-β–SMAD3 signaling and fibroblast-to-myofibroblast differentiation. Overall, these studies demonstrate that GSK3 could promote renal fibrosis by activation of TGF-β signaling and the use of GSK3 inhibitors might represent a novel therapeutic approach for progressive renal fibrosis that develops as a consequence of acute kidney injury.

Polycystic kidney diseases (PKDs) are inherited disorders characterized by the formation of fluid filled renal cysts. Elevated cAMP levels in PKDs stimulate progressive cyst enlargement involving cell proliferation and transepithelial fluid secretion often leading to end stage renal disease. The glycogen synthase kinase-3 (GSK3) family of protein kinases consists of GSK3α and GSK3β isoforms and plays a crucial role in multiple cellular signaling pathways. We previously found that GSK3β, a regulator of cell proliferation, is also crucial for cAMP generation and vasopressin mediated urine concentration by the kidneys. However, the role of GSK3β in the pathogenesis of PKDs is not known. Here we found that GSK3β expression and activity were markedly up-regulated and associated with cyst-lining epithelia in the kidneys of mice and humans with PKD. Renal collecting duct specific gene knockout of GSK3β or pharmacological inhibition of GSK3 effectively slowed the progression of PKD in mouse models of autosomal recessive or autosomal dominant PKD. GSK3 inactivation inhibited cAMP generation and cell proliferation resulting in reduced cyst expansion, improved renal function and extended lifespan. GSK3β inhibition also reduced pERK, c-Myc and Cyclin-D1, known mitogens in proliferation of cystic epithelial cells. Thus, GSK3β plays a novel functional role in PKD pathophysiology and its inhibition may be therapeutically useful to slow cyst expansion and progression of PKD.

Arginine vasopressin (AVP) and its type-2 receptor (V2R) play an essential role in the regulation of salt and water homeostasis by the kidneys. V2R activation also stimulates proliferation of renal cell carcinoma (RCC) cell lines in vitro. The current studies investigated V2R expression and activity in human RCC tumors, and its role in RCC tumor growth. Examination of the cancer genome atlas (TCGA) database, and analysis of human RCC tumor tissue microarrays, cDNA arrays and tumor biopsy samples demonstrated V2R expression and activity in clear cell RCC (ccRCC). In vitro, V2R antagonists OPC31260 and Tolvaptan, or V2R gene silencing reduced wound closure and cell viability of 786-O and Caki-1 human ccRCC cell lines. Similarly in mouse xenograft models, Tolvaptan and OPC31260 decreased RCC tumor growth by reducing cell proliferation and angiogenesis, while increasing apoptosis. In contrast, the V2R agonist dDAVP significantly increased tumor growth. High intracellular cAMP levels and ERK1/2 activation were observed in human ccRCC tumors. In mouse tumors and Caki-1 cells, V2R agonists reduced Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

As a cell-specific organelle, acrosome (Acr) and its formation are an important event for spermiogenesis. However, the Acr formation is far more complicated than has been proposed. In this study, we have cloned a novel membrane protein Afaf (Acr formation associated factor) that was expressed abundantly in the round spermatids, localized in the inner and outer membrane of forming Acrs, and declined in the maturing Acrs. In the transfected Hela cells, Afaf protein was localized in the plasma membrane, EEA1-positive early endosomes (EEs) and occasionally in the nuclei. Therefore, we propose that EEs and plasma membrane may be also directly involved in the Acr biogenesis.