Domon Magdalena M, Besson Françoise, Tylki-Szymanska Anna, Bandorowicz-Pikula Joanna, Pikula Slawomir
Department of Biochemistry, Nencki Institute of Experimental Biology, 3 Pasteur Street, 02-093 Warsaw, Poland.
Mol Biosyst. 2013 Apr 5;9(4):668-76. doi: 10.1039/c3mb25487a.
Niemann-Pick type C (NPC) disease is a lipid storage disorder characterized by accumulation of lipids in the late endosome/lysosome (LE/LY) compartment. In our previous report we isolated membranes of the LE/LY compartment from NPC L1 skin fibroblasts with a mutation in the NPC1 gene and found that they were characterized by low fluidity which likely contributed to the impaired function of membrane proteins involved in storage and turnover of cholesterol. In this report we isolated lipid microdomains (DRMs) from membranes of various cellular compartments and observed an increased amount of DRMs in the LE/LY compartment of NPC L1 cells in comparison to control cells, with no change in the DRM content in the plasma membrane. In addition, in the NPC cells, the majority of the cholesterol-interacting protein, AnxA6, which participates in the transport and distribution of cholesterol, translocated to DRMs upon a rise in Ca(2+) concentration. The mechanism of this translocation was further studied in vitro using Langmuir monolayers. We found that Ca(2+) is the main factor which regulates the interaction of AnxA6 with monolayers composed of neutral lipids, such as DPPC and sphingomyelin, and may also determine AnxA6 localization in cholesterol and sphingomyelin enriched microdomains, thus contributing to the etiology of the NPC disease.
尼曼-皮克C型（NPC）病是一种脂质贮积病，其特征是脂质在晚期内体/溶酶体（LE/LY）区室中蓄积。在我们之前的报告中，我们从NPC1基因突变的NPC L1皮肤成纤维细胞中分离出LE/LY区室的膜，发现它们的特点是流动性低，这可能导致参与胆固醇储存和周转的膜蛋白功能受损。在本报告中，我们从各种细胞区室的膜中分离出脂质微区（DRM），并观察到与对照细胞相比，NPC L1细胞的LE/LY区室中DRM的量增加，而质膜中的DRM含量没有变化。此外，在NPC细胞中，参与胆固醇运输和分布的大多数胆固醇相互作用蛋白AnxA6在Ca(2+)浓度升高时转移到DRM。使用朗缪尔单层在体外进一步研究了这种转移的机制。我们发现Ca(2+)是调节AnxA6与由中性脂质（如二棕榈酰磷脂酰胆碱和鞘磷脂）组成的单层相互作用的主要因素，并且还可能决定AnxA6在富含胆固醇和鞘磷脂的微区中的定位，从而导致NPC病的病因。
