Jaques Fabienne, Jousset Hélène, Tomas Alejandra, Prost Anne-Lise, Wollheim Claes B, Irminger Jean-Claude, Demaurex Nicolas, Halban Philippe A
Department of Genetic Medicine and Development, University of Geneva Medical Center, 1211 Geneva-4, Switzerland.
Endocrinology. 2008 May;149(5):2494-505. doi: 10.1210/en.2007-0974. Epub 2008 Jan 24.
Cell-to-cell interactions play an important role in insulin secretion. Compared with intact islets, dispersed pancreatic beta-cells show increased basal and decreased glucose-stimulated insulin secretion. In this study, we used mouse MIN6B1 cells to investigate the mechanisms that control insulin secretion when cells are in contact with each other or not. RNAi-mediated silencing of the adhesion molecule E-cadherin in confluent cells reduced glucose-stimulated secretion to the levels observed in isolated cells but had no impact on basal secretion. Dispersed cells presented high cytosolic Ca(2+) activity, depolymerized cytoskeleton and ERK1/2 activation in low glucose conditions. Both the increased basal secretion and the spontaneous Ca(2+) activity were corrected by transient removal of Ca(2+) or prolonged incubation of cells in low glucose, a procedure that restored the ability of dispersed cells to respond to glucose (11-fold stimulation). In conclusion, we show that dispersed pancreatic beta-cells can respond robustly to glucose once their elevated basal secretion has been corrected. The increased basal insulin secretion of dispersed cells is due to spontaneous Ca(2+) transients that activate downstream Ca(2+) effectors, whereas engagement of cell adhesion molecules including E-cadherin contributes to the greater secretory response to glucose seen in cells with normal intercellular contacts.
细胞间相互作用在胰岛素分泌中起重要作用。与完整胰岛相比，分散的胰腺β细胞基础胰岛素分泌增加，葡萄糖刺激的胰岛素分泌减少。在本研究中，我们使用小鼠MIN6B1细胞来研究细胞相互接触或不接触时控制胰岛素分泌的机制。通过RNA干扰介导的汇合细胞中粘附分子E-钙粘蛋白的沉默，可将葡萄糖刺激的分泌降低至分离细胞中观察到的水平，但对基础分泌无影响。在低葡萄糖条件下，分散的细胞呈现高细胞质Ca(2+)活性、解聚的细胞骨架和ERK1/2激活。通过短暂去除Ca(2+)或在低葡萄糖中长时间孵育细胞，可纠正基础分泌增加和自发Ca(2+)活性，该过程恢复了分散细胞对葡萄糖的反应能力（11倍刺激）。总之，我们表明，一旦分散的胰腺β细胞升高的基础分泌得到纠正，它们就能对葡萄糖作出强烈反应。分散细胞基础胰岛素分泌增加是由于自发Ca(2+)瞬变激活下游Ca(2+)效应器，而包括E-钙粘蛋白在内的细胞粘附分子的参与有助于正常细胞间接触的细胞对葡萄糖产生更大的分泌反应。
