Cossec Jack-Christophe, Simon Anne, Marquer Catherine, Moldrich Randal X, Leterrier Christophe, Rossier Jean, Duyckaerts Charles, Lenkei Zsolt, Potier Marie-Claude
Centre de Recherche de l'Institut du Cerveau et de la Moelle, CNRS UMRS7225 INSERM UMRS975 UPMC, Hôpital de La Salpêtrière, 75651, Paris Cedex 13, France.
Biochim Biophys Acta. 2010 Aug;1801(8):846-52. doi: 10.1016/j.bbalip.2010.05.010. Epub 2010 May 24.
Several lines of evidence support a strong relationship between cholesterol and Alzheimer's disease pathogenesis. Membrane cholesterol is known to modulate amyloid precursor protein (APP) endocytosis and amyloid-beta (Abeta) secretion. Here we show in a human cell line model of endocytosis (HEK293 cells) that cholesterol exerts these effects in a dose-dependent and linear manner, over a wide range of concentrations (-40% to +40% variations of plasma membrane cholesterol induced by methyl-beta-cyclodextrin (MBCD) and MBCD-cholesterol complex respectively). We found that the gradual effect of cholesterol is inhibited by small interference RNA-mediated downregulation of clathrin. Modulation of clathrin-mediated APP endocytosis by cholesterol was further demonstrated using mutants of proteins involved in the formation of early endosomes (dynamin2, Eps15 and Rab5). Importantly we show that membrane proteins other than APP are not affected by cholesterol to the same extent. Indeed clathrin-dependent endocytosis of transferrin and cannabinoid1 receptors as well as internalization of surface proteins labelled with a biotin derivative (sulfo-NHS-SS-biotin) were not sensitive to variations of plasma membrane cholesterol from -40% to 40%. In conclusion clathrin-dependent APP endocytosis appears to be very sensitive to the levels of membrane cholesterol. These results suggest that cholesterol increase in AD could be responsible for the enhanced internalization of clathrin-, dynamin2-, Eps15- and Rab5-dependent endocytosis of APP and the ensuing overproduction of Abeta.
多条证据支持胆固醇与阿尔茨海默病发病机制之间存在密切关系。已知膜胆固醇可调节淀粉样前体蛋白（APP）的内吞作用和β淀粉样蛋白（Aβ）的分泌。在此，我们在一种内吞作用的人类细胞系模型（HEK293细胞）中表明，胆固醇在很宽的浓度范围内（分别由甲基-β-环糊精（MBCD）和MBCD-胆固醇复合物诱导的质膜胆固醇-40%至+40%的变化）以剂量依赖性和线性方式发挥这些作用。我们发现，网格蛋白的小干扰RNA介导的下调抑制了胆固醇的渐进作用。使用参与早期内体形成的蛋白质（发动蛋白2、Eps15和Rab5）的突变体进一步证明了胆固醇对网格蛋白介导的APP内吞作用的调节。重要的是，我们表明APP以外的膜蛋白受胆固醇的影响程度不同。事实上，转铁蛋白和大麻素1受体的网格蛋白依赖性内吞作用以及用生物素衍生物（磺基-NHS-SS-生物素）标记的表面蛋白的内化对质膜胆固醇从-40%到40%的变化不敏感。总之，网格蛋白依赖性APP内吞作用似乎对膜胆固醇水平非常敏感。这些结果表明，阿尔茨海默病中胆固醇的增加可能是APP的网格蛋白、发动蛋白2、Eps15和Rab5依赖性内吞作用增强以及随后Aβ过量产生的原因。
