Department of Immunology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.
J Immunol. 2011 Apr 1;186(7):4088-97. doi: 10.4049/jimmunol.1001139. Epub 2011 Feb 21.
B cell chemotaxis occurs in response to specific chemokine gradients and is critical for homeostasis and immune response. The molecular regulation of B cell membrane-actin interactions during migration is poorly understood. In this study, we report a role for ezrin, a member of the membrane-cytoskeleton cross-linking ezrin-radixin-moesin proteins, in the regulation of the earliest steps of B cell polarization and chemotaxis. We visualized chemokine-induced changes in murine B cell morphology using scanning electron microscopy and spatiotemporal dynamics of ezrin in B cells using epifluorescence and total internal reflection microscopy. Upon chemokine stimulation, ezrin is transiently dephosphorylated to assume an inactive conformation and localizes to the lamellipodia. B cells expressing a phosphomimetic conformationally active mutant of ezrin or those in which ezrin dephosphorylation was pharmacologically inhibited displayed impaired microvillar dynamics, morphological polarization, and chemotaxis. Our data suggest a 2-fold involvement of ezrin in B cell migration, whereby it first undergoes chemokine-induced dephosphorylation to facilitate membrane flexibility, followed by relocalization to the actin-rich lamellipodia for dynamic forward protrusion of the cells.
B 细胞趋化作用是对特定趋化因子梯度的反应，对于体内平衡和免疫反应至关重要。在迁移过程中，B 细胞膜-肌动蛋白相互作用的分子调控还知之甚少。在这项研究中，我们报告了膜细胞骨架交联蛋白 ezrin 在调节 B 细胞极化和趋化作用的最早步骤中的作用。我们使用扫描电子显微镜观察了趋化因子诱导的小鼠 B 细胞形态变化，并用荧光显微镜和全内反射显微镜观察了 B 细胞中 ezrin 的时空动力学。在趋化因子刺激下，ezrin 被短暂去磷酸化以呈现非活性构象，并定位于片足。表达磷酸模拟构象激活突变体 ezrin 的 B 细胞或通过药理学抑制 ezrin 去磷酸化的 B 细胞显示出微绒毛动力学、形态极化和趋化作用受损。我们的数据表明 ezrin 在 B 细胞迁移中具有双重作用，首先它经历趋化因子诱导的去磷酸化以促进膜的柔韧性，然后重新定位到富含肌动蛋白的片足，以动态地向前推进细胞。
