Lehtonen Sanna, Shah Mehul, Nielsen Rikke, Iino Noriaki, Ryan Jennifer J, Zhou Huilin, Farquhar Marilyn G
Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093, USA.
Mol Biol Cell. 2008 Jul;19(7):2949-61. doi: 10.1091/mbc.e07-05-0521. Epub 2008 Apr 16.
Numerous proteins involved in endocytosis at the plasma membrane have been shown to be present at novel intracellular locations and to have previously unrecognized functions. ARH (autosomal recessive hypercholesterolemia) is an endocytic clathrin-associated adaptor protein that sorts members of the LDL receptor superfamily (LDLR, megalin, LRP). We report here that ARH also associates with centrosomes in several cell types. ARH interacts with centrosomal (gamma-tubulin and GPC2 and GPC3) and motor (dynein heavy and intermediate chains) proteins. ARH cofractionates with gamma-tubulin on isolated centrosomes, and gamma-tubulin and ARH interact on isolated membrane vesicles. During mitosis, ARH sequentially localizes to the nuclear membrane, kinetochores, spindle poles and the midbody. Arh(-/-) embryonic fibroblasts (MEFs) show smaller or absent centrosomes suggesting ARH plays a role in centrosome assembly. Rat-1 fibroblasts depleted of ARH by siRNA and Arh(-/-) MEFs exhibit a slower rate of growth and prolonged cytokinesis. Taken together the data suggest that the defects in centrosome assembly in ARH depleted cells may give rise to cell cycle and mitotic/cytokinesis defects. We propose that ARH participates in centrosomal and mitotic dynamics by interacting with centrosomal proteins. Whether the centrosomal and mitotic functions of ARH are related to its endocytic role remains to be established.
众多参与质膜内吞作用的蛋白质已被证明存在于新的细胞内位置,并具有以前未被认识的功能。ARH(常染色体隐性高胆固醇血症)是一种与网格蛋白相关的内吞衔接蛋白,可对低密度脂蛋白受体超家族(低密度脂蛋白受体、巨膜蛋白、低密度脂蛋白受体相关蛋白)的成员进行分类。我们在此报告,ARH在几种细胞类型中也与中心体相关联。ARH与中心体蛋白(γ-微管蛋白、GPC2和GPC3)以及运动蛋白(动力蛋白重链和中间链)相互作用。在分离的中心体上,ARH与γ-微管蛋白共分离,并且在分离的膜泡上γ-微管蛋白和ARH相互作用。在有丝分裂期间,ARH依次定位于核膜、动粒、纺锤极和中体。Arh(-/-)胚胎成纤维细胞(MEF)显示中心体较小或缺失,这表明ARH在中心体组装中起作用。通过小干扰RNA使ARH缺失的大鼠-1成纤维细胞和Arh(-/-) MEF表现出生长速度减慢和胞质分裂延长。综合这些数据表明,ARH缺失细胞中中心体组装的缺陷可能导致细胞周期以及有丝分裂/胞质分裂缺陷。我们提出,ARH通过与中心体蛋白相互作用参与中心体和有丝分裂动力学。ARH的中心体和有丝分裂功能是否与其内吞作用相关仍有待确定。