Arcones Alba C, Vila-Bedmar Rocío, Mirasierra Mercedes, Cruces-Sande Marta, Vallejo Mario, Jones Ben, Tomas Alejandra, Mayor Federico, Murga Cristina
Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (CBMSO) UAM-CSIC; Instituto de Investigación Sanitaria Hospital Universitario La Princesa; CIBER de Enfermedades Cardiovasculares (CIBERCV), UNIVERSIDAD AUTONOMA DE MADRID and Instituto de Salud Carlos III, Madrid, Spain.
Departamento de Ciencias Básicas de la Salud, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos (URJC), Madrid, Spain.
BMC Biol. 2021 Mar 3;19(1):40. doi: 10.1186/s12915-021-00966-w.
Insulin secretion from the pancreatic β-cell is finely modulated by different signals to allow an adequate control of glucose homeostasis. Incretin hormones such as glucagon-like peptide-1 (GLP-1) act as key physiological potentiators of insulin release through binding to the G protein-coupled receptor GLP-1R. Another key regulator of insulin signaling is the Ser/Thr kinase G protein-coupled receptor kinase 2 (GRK2). However, whether GRK2 affects insulin secretion or if GRK2 can control incretin actions in vivo remains to be analyzed.
Using GRK2 hemizygous mice, isolated pancreatic islets, and model β-cell lines, we have uncovered a relevant physiological role for GRK2 as a regulator of incretin-mediated insulin secretion in vivo. Feeding, oral glucose gavage, or administration of GLP-1R agonists in animals with reduced GRK2 levels (GRK2+/- mice) resulted in enhanced early phase insulin release without affecting late phase secretion. In contrast, intraperitoneal glucose-induced insulin release was not affected. This effect was recapitulated in isolated islets and correlated with the increased size or priming efficacy of the readily releasable pool (RRP) of insulin granules that was observed in GRK2+/- mice. Using nanoBRET in β-cell lines, we found that stimulation of GLP-1R promoted GRK2 association to this receptor and that GRK2 protein and kinase activity were required for subsequent β-arrestin recruitment.
Overall, our data suggest that GRK2 is an important negative modulator of GLP-1R-mediated insulin secretion and that GRK2-interfering strategies may favor β-cell insulin secretion specifically during the early phase, an effect that may carry interesting therapeutic applications.
胰腺β细胞的胰岛素分泌受到不同信号的精细调节，以实现对葡萄糖稳态的充分控制。肠促胰岛素激素，如胰高血糖素样肽-1（GLP-1），通过与G蛋白偶联受体GLP-1R结合，作为胰岛素释放的关键生理增强剂。胰岛素信号传导的另一个关键调节因子是丝氨酸/苏氨酸激酶G蛋白偶联受体激酶2（GRK2）。然而，GRK2是否影响胰岛素分泌，或者GRK2是否能在体内控制肠促胰岛素的作用，仍有待分析。
使用GRK2半合子小鼠、分离的胰岛和模型β细胞系，我们发现GRK2作为体内肠促胰岛素介导的胰岛素分泌调节因子具有重要的生理作用。在GRK2水平降低的动物（GRK2+/-小鼠）中喂食、口服葡萄糖灌胃或给予GLP-1R激动剂，可增强早期胰岛素释放，而不影响晚期分泌。相比之下，腹腔注射葡萄糖诱导的胰岛素释放不受影响。这种效应在分离的胰岛中得到重现，并与GRK2+/-小鼠中观察到的胰岛素颗粒易释放池（RRP）大小增加或启动效率提高相关。使用β细胞系中的纳米BRET技术，我们发现刺激GLP-1R可促进GRK2与该受体的结合，并且GRK2蛋白和激酶活性是随后β-arrestin募集所必需的。
总体而言，我们的数据表明GRK2是GLP-1R介导的胰岛素分泌的重要负调节因子，并且干扰GRK2的策略可能特别在早期有利于β细胞胰岛素分泌，这一效应可能具有有趣的治疗应用。
