ARHGAP21 inibe a secreção de insulina estimulada por glicose através da modulação aa FAK, CDC42 E PKC dzeta / ARHGAP21 inhibits glucose-stimulated insulin secretion through through FAK, CDC42 and PKC dzeta

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

26/06/2011

RESUMO

Background/Aims: ARHGAP21 is a Rho-GAP that promotes activation of the Rho-GTPase Cdc42 intrinsic factor, which is responsible for the hydrolysis of GTP to GDP and those proteins inactivation. ARHGAP21 associates with PKC? in cardiomyocytes and to the C-terminal portion of FAK in glioblastoma, inhibiting Rho-GTPases and actin cytoskeleton rearrangement. Cdc42, FAK and PKC? promote glucose-stimulated insulin secretion, differentiation and proliferation in pancreatic islets. The aim this study was to assess in pancreatic beta cells: 1) ARHGAP21 expression and localization; 2) glucose effect in PKC?, FAK e Cdc42 expression and association to ARHGAP21; 3) The role of ARHGAP21 on glucose-stimulated insulin secretion. Materials and Methods: ARHGAP21 expression and localization in MIN6 cells were evaluated by immunofluorescence. MIN6 cells were treated with glucose (5.6 mM and 22 mM) or insulin (0.2 U/ml) for 3 days. After protein extraction, the ARHGAP21, PKC?, FAK e Cdc42 expressions were evaluated by Western blot. MIN6 cells were exposed for 0, 5, 15, e 30 min to 22 mM of glucose. ARHGAP21/FAK and ARHGAP21/PKC? interactions were evaluated for immunopreciption and phosphorylation of FAK in tyrosine 397 and 925 and phosphorylation of PKC? in threonine 410. The expression of these proteins also was evaluated in pancreatic islets of neonates Swiss mice previously treated for 2 days with 1 nM of ARHGAP21 antisense or mismatch oligonucleotides. These islets were incubated with 2.8 mM or 16.7 mM of glucose and insulin secretion was evaluated. Results: ARHGAP21 is localized in the cytoplasm, mainly the plasmatic membrane. Glucose reduced ARHGAP21 and PKC? expression but not altered FAK and Cdc42 expression, while insulin had no effect whatsoever on the expression of the studied proteins. Glucose also dissociated ARHGAP21/FAK, leading to increased FAK phosphorylation, which was followed by ARHGAP21/PKC? association and reduced Thr410 PKC? phosphorylation. ARHGAP21 Knockdown mice pancreatic islets had lower PKC? and higher Cdc42 expression, and also increased insulin secretion in both sub- (2.8 mM) and supra-stimulatory (16.7 mM) of glucose conditions. Conclusions: ARHGAP21 modulates Cdc42 and FAK, proteins responsible for rearrangement of actin cytoskeleton and extrusion of insulin vesicles, and reducing their expression leads to inhibited insulin secretion. Furthermore, we observed that glucose modulates ARHGAP21/FAK and ARHGAP21/ PKC? interactions

ASSUNTO(S)

gene arhgap21 glicose insulina - secreção filamentos de actina arhgap21 gene glucose insulina cytoskeletal proteins proteinas citoesqueleto actin

ACESSO AO ARTIGO

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