Victoria Research Laboratories, Room A5-140, 800 Commissioners Road East, London, Ontario N6C 2V5, Canada.
Endocrinology. 2011 Feb;152(2):424-35. doi: 10.1210/en.2010-0877. Epub 2010 Dec 22.
β1-integrin is a well-established regulator of β-cell activities; however, the role of its associated α-subunits is relatively unknown. Previously, we have shown that human fetal islet and INS-1 cells highly express α3β1-integrin and that collagens I and IV significantly enhance their survival and function; in addition, blocking β1 function in the fetal islet cells decreased adhesion on collagen I and increased apoptosis. The present study investigates the effect of blocking α3. Using α3 blocking antibody or small interfering RNA, the effects of α3-integrin blockade were examined in isolated human fetal or adult islet cells or INS-1 cells, cultured on collagens I or IV. In parallel, β1 blockade was analyzed in INS-1 cells. Perturbing α3 function in human islet or INS-1 cells resulted in significant decreases in cell function (adhesion, spreading, proliferation and Pdx1 and insulin expression/secretion), primarily on collagen IV. A significant decrease in focal adhesion kinase and ERK1/2 phosphorylation and increased caspase3 cleavage were observed on both collagens. These effects were similar to changes after β1 blockade. Interestingly, only α3 blockade reduced expression of phospho-Akt and members of its downstream signaling cascades (glycogen synthase kinase β and X-linked inhibitor of apoptosis), demonstrating a specific effect of α3 on the phosphatidylinositol 3-kinase/Akt pathway. These results suggest that α3- as well as β1-integrin-extracellular matrix interactions are critical for modulating β-cell survival and function through specialized signaling cascades and enhance our understanding of how to improve islet microenvironments for cell-based treatments of diabetes.
β1-整合素是一种公认的β细胞活性调节剂；然而，其相关的α亚基的作用相对未知。以前，我们已经表明，人胎儿胰岛和 INS-1 细胞高度表达α3β1-整合素，胶原 I 和 IV 显著增强它们的存活和功能；此外，在胎儿胰岛细胞中阻断β1 功能会降低对胶原 I 的黏附，并增加细胞凋亡。本研究调查了阻断α3 的作用。使用α3 阻断抗体或小干扰 RNA，在分离的人胎儿或成年胰岛细胞或 INS-1 细胞上，在胶原 I 或 IV 上培养，研究了α3-整合素阻断的影响。同时，在 INS-1 细胞中分析了β1 阻断。在人胰岛或 INS-1 细胞中干扰α3 功能会导致细胞功能（黏附、扩展、增殖和 Pdx1 和胰岛素表达/分泌）显著降低，主要是在胶原 IV 上。在两种胶原上都观察到粘着斑激酶和 ERK1/2 磷酸化的显著减少和 caspase3 切割的增加。这些变化与β1 阻断后的变化相似。有趣的是，只有α3 阻断减少了磷酸化 Akt 的表达及其下游信号级联（糖原合酶激酶β和 X 连锁凋亡抑制剂）的成员，表明α3 对磷脂酰肌醇 3-激酶/Akt 途径有特异性作用。这些结果表明，α3-以及β1-整合素-细胞外基质相互作用对于通过专门的信号级联调节β细胞的存活和功能至关重要，并增强了我们对如何改善胰岛微环境以用于基于细胞的糖尿病治疗的理解。
