期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：17
页码：7999-8004
DOI：10.1073/pnas.1003655107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Therapeutic strategies that augment insulin release from pancreatic {beta}-cells are considered beneficial in the treatment of type 2 diabetes. We previously demonstrated that activation of {beta}-cell M3 muscarinic receptors (M3Rs) greatly promotes glucose-stimulated insulin secretion (GSIS), suggesting that strategies aimed at enhancing signaling through {beta}-cell M3Rs may become therapeutically useful. M3R activation leads to the stimulation of G proteins of the Gq family, which are under the inhibitory control of proteins known as regulators of G protein signaling (RGS proteins). At present, it remains unknown whether RGS proteins play a role in regulating insulin release. To address this issue, we initially demonstrated that MIN6 insulinoma cells express functional M3Rs and that RGS4 was by far the most abundant RGS protein expressed by these cells. Strikingly, siRNA-mediated knockdown of RGS4 expression in MIN6 cells greatly enhanced M3R-mediated augmentation of GSIS and calcium release. We obtained similar findings using pancreatic islets prepared from RGS4-deficient mice. Interestingly, RGS4 deficiency had little effect on insulin release caused by activation of other {beta}-cell GPCRs. Finally, treatment of mutant mice selectively lacking RGS4 in pancreatic {beta}-cells with a muscarinic agonist (bethanechol) led to significantly increased plasma insulin and reduced blood glucose levels, as compared to control littermates. Studies with {beta}-cell-specific M3R knockout mice showed that these responses were mediated by {beta}-cell M3Rs. These findings indicate that RGS4 is a potent negative regulator of M3R function in pancreatic {beta}-cells, suggesting that RGS4 may represent a potential target to promote insulin release for therapeutic purposes.
