Departments of Medicine, Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
Traffic. 2010 Mar;11(3):348-60. doi: 10.1111/j.1600-0854.2009.01022.x. Epub 2009 Dec 3.
Caveolae are plasma membrane domains involved in the uptake of certain pathogens and toxins. Internalization of some cell surface integrins occurs via caveolae suggesting caveolae may play a crucial role in modulating integrin-mediated adhesion and cell migration. Here we demonstrate a critical role for gangliosides (sialo-glycosphingolipids) in regulating caveolar endocytosis in human skin fibroblasts. Pretreatment of cells with endoglycoceramidase (cleaves glycosphingolipids) or sialidase (modifies cell surface gangliosides and glycoproteins) selectively inhibited caveolar endocytosis by >70%, inhibited the formation of plasma membrane domains enriched in sphingolipids and cholesterol ('lipid rafts'), reduced caveolae and caveolin-1 at the plasma membrane by approximately 80%, and blunted activation of beta1-integrin, a protein required for caveolar endocytosis in these cells. These effects could be reversed by a brief incubation with gangliosides (but not with asialo-gangliosides or other sphingolipids) at 10 degrees C, suggesting that sialo-lipids are critical in supporting caveolar endocytosis. Endoglycoceramidase treatment also caused a redistribution of focal adhesion kinase, paxillin, talin, and PIP Kinase Igamma away from focal adhesions. The effects of sialidase or endoglycoceramidase on membrane domains and the distribution of caveolin-1 could be recapitulated by beta1-integrin knockdown. These results suggest that both gangliosides and beta1-integrin are required for maintenance of caveolae and plasma membrane domains.
小窝是参与某些病原体和毒素摄取的质膜结构域。某些细胞表面整合素的内化是通过小窝进行的，这表明小窝可能在调节整合素介导的黏附和细胞迁移中发挥关键作用。在这里，我们证明了神经节苷脂（唾液酸糖脂）在调节人皮肤成纤维细胞小窝内吞中的关键作用。用内切糖苷酶（裂解糖脂）或神经氨酸酶（修饰细胞表面神经节苷脂和糖蛋白）预处理细胞可选择性地抑制小窝内吞>70%，抑制富含鞘脂和胆固醇的质膜域的形成（“脂筏”），使质膜上的小窝和小窝蛋白-1减少约 80%，并削弱β1-整合素的激活，β1-整合素是这些细胞中小窝内吞所必需的蛋白。这些作用可以通过在 10°C 下用神经节苷脂（但不是用唾液酸神经节苷脂或其他鞘脂）短暂孵育来逆转，这表明唾液酸脂质对于支持小窝内吞至关重要。内切糖苷酶处理还导致粘着斑激酶、桩蛋白、talin 和 PIP Kinase Igamma 从粘着斑重新分布。神经氨酸酶或内切糖苷酶对膜域和小窝蛋白-1分布的影响可以通过β1-整合素的敲低来再现。这些结果表明，神经节苷脂和β1-整合素对于小窝和质膜域的维持都是必需的。
