Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
J Neuroinflammation. 2011 Nov 10;8:157. doi: 10.1186/1742-2094-8-157.
As the primary resident immune cells, microglia play a central role in regulating inflammatory processes in the CNS. The extracellular matrix (ECM) protein vitronectin promotes microglial activation, switching microglia into an activated phenotype. We have shown previously that microglia express two vitronectin receptors, αvβ3 and αvβ5 integrins. As these integrins have well-defined roles in activation and phagocytic processes in other cell types, the purpose of the current study was to investigate the contribution of these two integrins in microglial activation.
Microglial cells were prepared from wild-type, β3 integrin knockout (KO), β5 integrin KO or β3/β5 integrin DKO mice, and their interactions and activation responses to vitronectin examined in a battery of assays, including adhesion, expression of activation markers, MMP-9 expression, and phagocytosis. Expression of other αv integrins was examined by flow cytometry and immunoprecipitation.
Surprisingly, when cultured on vitronectin, microglia from the different knockout strains showed no obvious defects in adhesion, activation marker expression, MMP-9 induction, or phagocytosis of vitronectin-coated beads. To investigate the reason for this lack of effect, we examined the expression of other αv integrins. Flow cytometry showed that β3/β5 integrin DKO microglia expressed residual αv integrin at the cell surface, and immunoprecipitation confirmed this finding by revealing the presence of low levels of the αvβ1 and αvβ8 integrins. β1 integrin blockade had no impact on adhesion of β3/β5 integrin DKO microglia to vitronectin, suggesting that in addition to αvβ1, αvβ3, and αvβ5, αvβ8 also serves as a functional vitronectin receptor on microglia.
Taken together, this demonstrates that the αvβ3 and αvβ5 integrins are not essential for mediating microglial activation responses to vitronectin, but that microglia use multiple redundant receptors to mediate interactions with this ECM protein.
作为主要的常驻免疫细胞，小胶质细胞在调节中枢神经系统中的炎症过程中起着核心作用。细胞外基质（ECM）蛋白 vitronectin 促进小胶质细胞激活，将小胶质细胞转变为激活表型。我们之前已经表明，小胶质细胞表达两种 vitronectin 受体，αvβ3 和 αvβ5 整联蛋白。由于这些整联蛋白在其他细胞类型的激活和吞噬过程中具有明确的作用，因此本研究的目的是研究这两种整合素在小胶质细胞激活中的作用。
从小鼠中分离出野生型、β3 整合素敲除（KO）、β5 整合素 KO 或β3/β5 整合素双敲除（DKO）的小胶质细胞，并在一系列测定中检查它们与 vitronectin 的相互作用和激活反应，包括粘附、激活标志物表达、MMP-9 表达和吞噬作用。通过流式细胞术和免疫沉淀法检查其他αv 整联蛋白的表达。
令人惊讶的是，当在 vitronectin 上培养时，来自不同敲除株的小胶质细胞在粘附、激活标志物表达、MMP-9 诱导或吞噬 vitronectin 包被珠方面没有明显缺陷。为了研究这种缺乏效应的原因，我们检查了其他αv 整联蛋白的表达。流式细胞术显示β3/β5 整合素双敲除小胶质细胞在细胞表面表达残留的αv 整联蛋白，免疫沉淀证实了这一发现，揭示了低水平的αvβ1 和αvβ8 整联蛋白的存在。β1 整联蛋白阻断对β3/β5 整合素 DKO 小胶质细胞与 vitronectin 的粘附没有影响，表明除了αvβ1、αvβ3 和αvβ5 外，αvβ8 也作为小胶质细胞上的功能性 vitronectin 受体。
综上所述，这表明αvβ3 和αvβ5 整联蛋白对于介导小胶质细胞对 vitronectin 的激活反应不是必需的，但小胶质细胞使用多种冗余受体来介导与这种 ECM 蛋白的相互作用。
