RESUMO
Dishevelled (Dvl/Dsh) is a key scaffold protein that propagates Wnt signaling essential for embryogenesis and homeostasis. However, whether the antagonism of Wnt signaling that is necessary for vertebrate head formation can be achieved through regulation of Dsh protein stability is unclear. Here, we show that membrane-associated RING-CH2 (March2), a RING-type E3 ubiquitin ligase, antagonizes Wnt signaling by regulating the turnover of Dsh protein via ubiquitin-mediated lysosomal degradation in the prospective head region of Xenopus We further found that March2 acquires regional and functional specificities for head formation from the Dsh-interacting protein Dapper1 (Dpr1). Dpr1 stabilizes the interaction between March2 and Dsh in order to mediate ubiquitylation and the subsequent degradation of Dsh protein only in the dorso-animal region of Xenopus embryo. These results suggest that March2 restricts cytosolic pools of Dsh protein and reduces the need for Wnt signaling in precise vertebrate head development.
Assuntos
Proteínas Desgrenhadas/metabolismo , Cabeça/embriologia , Ubiquitina-Proteína Ligases/metabolismo , Proteínas de Xenopus/metabolismo , Animais , Técnicas de Cultura de Células , Imunofluorescência , Regulação da Expressão Gênica no Desenvolvimento , Hibridização In Situ , Morfogênese/genética , Proteólise , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais , Ubiquitinação/genética , Proteínas Wnt/metabolismo , Xenopus laevis/embriologia , Xenopus laevis/metabolismoRESUMO
Cyclin G2 (CCNG2) is an atypical cyclin that inhibits cell cycle progression and is often dysregulated in human cancers. Cyclin G2 in the occurrence and development of diabetic nephropathy (DN), one of the most severe diabetic complications, has not been fully identified. In this study, we investigated the function and regulatory mechanism of cyclin G2 in DN. In vivo studies revealed that a deficiency of cyclin G2 significantly increased albuminuria and promoted tubulointerstitial fibrosis in established DN. Cyclin G2 regulated the expression of fibrosis-related proteins via the canonical Wnt signalling pathway in renal tubular epithelial cells. Moreover, the binding of cyclin G2 to Dapper1 (Dpr1/DACT1), a protein involved in Wnt signalling, decreased the phosphorylation of Dpr1 at Ser762 by casein kinase 1 (CK1) and suppressed the Wnt signalling pathway. These findings reveal that cyclin G2 can protect against renal injury and fibrosis associated with DN and, thus, is a new target for the prevention and treatment of diabetic complications.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Ciclina G2/metabolismo , Túbulos Renais/patologia , Proteínas Nucleares/metabolismo , Proteínas de Ligação a RNA/metabolismo , Via de Sinalização Wnt , Albuminúria/complicações , Albuminúria/genética , Animais , Caseína Quinase I/metabolismo , Ciclina G2/deficiência , Nefropatias Diabéticas/complicações , Nefropatias Diabéticas/genética , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/genética , Fibrose , Glucose/toxicidade , Humanos , Camundongos Endogâmicos C57BL , Modelos Biológicos , Fosforilação/efeitos dos fármacos , Fosfosserina/metabolismo , Ligação Proteica/efeitos dos fármacos , Índice de Gravidade de DoençaRESUMO
Studies have shown that hepatic insulin resistance, a disorder of glucose and lipid metabolism, plays a vital role in type 2 diabetes (T2D). To clarify the function of Dapper1 in glucose and lipid metabolism in the liver, we investigated the relationships between Dapper1 and adenosine triphosphate (ATP)- and Ca2+-mediated activation of PI3K/Akt. We observed a reduction in hepatic Dapper1 in db/db (mice that are homozygous for a spontaneous diabetes mutation) and HFD-induced diabetic mice with T2D. Hepatic overexpression of Dapper1 improved hyperglycemia, insulin resistance, and fatty liver. It also increased Akt (pAkt) signaling and repressed both gluconeogenesis and lipogenesis. Conversely, Ad-shDapper1-induced knockdown of hepatic Dapper1 promoted gluconeogenesis and lipogenesis. Furthermore, Dapper1 activated PI3K p110α/Akt in an insulin-independent manner by inducing ATP production and secretion in vitro. Blockade of P2 ATP receptors, the downstream phospholipase C (PLC), or the inositol triphosphate receptor (IP3R all reduced the Dapper1-induced increase in cytosolic free calcium and Dapper1-mediated PI3K/Akt activation, as did removal of calcium in the medium. In conclusion, Dapper1 attenuates hepatic gluconeogenesis and lipogenesis in T2D.