Frank M, van der Haar M E, Schaeren-Wiemers N, Schwab M E
Research Institute, University of Zurich and Swiss Federal Institute of Technology Zurich, CH-8029 Zurich, Switzerland.
J Neurosci. 1998 Jul 1;18(13):4901-13. doi: 10.1523/JNEUROSCI.18-13-04901.1998.
rMAL, the rat myelin and lymphocyte protein, is a small hydrophobic protein of 17 kDa with four putative transmembrane domains and is expressed in oligodendrocytes and Schwann cells, the myelinating cells of the nervous system. In addition, transcript expression has been found in kidney, spleen, and intestine. Confocal microscopy and immunoelectron microscopy with an affinity-purified antibody localized rMAL to compact myelin in a pattern similar to the structural myelin proteins: myelin basic protein and proteolipid protein. In kidney and stomach epithelia, rMAL is located almost exclusively on the apical (luminal) membranes of the cells lining distal tubuli in kidney and the glandular part of the stomach. Biochemical analysis of plasma membranes isolated from spinal cord and kidney demonstrated that rMAL is a proteolipid that is present in detergent insoluble complexes typical for proteins associated with glycosphingolipids. Lipid and protein analysis showed a co-enrichment of glycosphingolipids and rMAL protein within these complexes, indicating a close association of rMAL to glycosphingolipids in myelin and in kidney in vivo. We conclude that specific rMAL-glycosphingolipid interactions may lead to the formation and maintenance of stable protein-lipid microdomains in myelin and apical epithelial membranes. They may contribute to specific properties of these highly specialized plasma membranes.
大鼠髓鞘与淋巴细胞蛋白（rMAL）是一种17 kDa的小疏水蛋白，具有四个假定的跨膜结构域，在少突胶质细胞和施万细胞（神经系统的髓鞘形成细胞）中表达。此外，在肾脏、脾脏和肠道中也发现了转录本表达。利用亲和纯化抗体进行的共聚焦显微镜和免疫电子显微镜观察将rMAL定位到致密髓鞘中，其模式类似于结构性髓鞘蛋白：髓鞘碱性蛋白和蛋白脂质蛋白。在肾脏和胃上皮中，rMAL几乎只位于肾远曲小管内衬细胞的顶端（管腔）膜以及胃的腺部。对从脊髓和肾脏分离的质膜进行的生化分析表明，rMAL是一种蛋白脂质，存在于与糖鞘脂相关蛋白典型的去污剂不溶性复合物中。脂质和蛋白质分析显示，这些复合物中糖鞘脂和rMAL蛋白共同富集，表明在体内髓鞘和肾脏中rMAL与糖鞘脂紧密相关。我们得出结论，特定的rMAL - 糖鞘脂相互作用可能导致髓鞘和顶端上皮细胞膜中稳定的蛋白质 - 脂质微结构域的形成和维持。它们可能有助于这些高度特化质膜的特定特性。
