Michaux G, Gansmuller A, Hindelang C, Labouesse M
Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, BP163, 1 rue Laurent Fries, 67404, Illkirch, France.
Curr Biol. 2000 Sep 21;10(18):1098-107. doi: 10.1016/s0960-9822(00)00695-3.
Polarised trafficking of proteins is critical for normal expression of the epithelial phenotype, but its genetic control is not understood. The regulatory gene lin-26 is essential for normal epithelial differentiation in the nematode Caenorhabditis elegans. To identify potential effectors of lin-26, we characterised mutations that result in lin-26-like phenotypes. Here, we report the phenotypic and molecular analysis of one such mutant line, che-14.
Mutations in che-14 resulted in several partially penetrant phenotypes affecting the function of most epithelial or epithelial-like cells of the ectoderm, including the hypodermis, excretory canal, vulva, rectum and several support cells. The defects were generally linked to the accumulation of vesicles or amorphous material near the apical surface, suggesting that secretion was defective. The CHE-14 protein showed similarity to proteins containing sterol-sensing domains, including Dispatched, Patched and NPC1. A fusion protein between full-length CHE-14 and the green fluorescent protein became localised to the apical surface of epithelial cells that require che-14 function. Deletions that removed the predicted transmembrane domains or extracellular loops of CHE-14 abolished apical localisation and function of the protein.
We propose that CHE-14 is involved in a novel secretory pathway dedicated to the exocytosis of lipid-modified proteins at the apical surface of certain epithelial cells. Our data raise the possibility that the primordial function of proteins containing a sterol-sensing domain is to control vesicle trafficking: CHE-14 and Dispatched in exocytosis, Patched and NPC1 in endocytosis.
蛋白质的极化运输对于上皮细胞表型的正常表达至关重要，但其遗传控制机制尚不清楚。调控基因lin-26对线虫秀丽隐杆线虫的正常上皮分化至关重要。为了鉴定lin-26的潜在效应因子，我们对导致lin-26样表型的突变进行了表征。在此，我们报告了一个这样的突变株系che-14的表型和分子分析。
che-14中的突变导致了几种部分显性的表型，影响了外胚层的大多数上皮或上皮样细胞的功能，包括皮下组织、排泄管、阴门、直肠和几个支持细胞。这些缺陷通常与顶端表面附近囊泡或无定形物质的积累有关，表明分泌存在缺陷。CHE-14蛋白与包含固醇感应结构域的蛋白相似，包括Dispatched、Patched和NPC1。全长CHE-14与绿色荧光蛋白之间的融合蛋白定位于需要che-14功能的上皮细胞的顶端表面。去除CHE-14预测的跨膜结构域或细胞外环的缺失消除了该蛋白的顶端定位和功能。
我们提出CHE-14参与了一种新的分泌途径，该途径专门用于在某些上皮细胞的顶端表面进行脂质修饰蛋白的胞吐作用。我们的数据增加了一种可能性，即包含固醇感应结构域的蛋白质的原始功能是控制囊泡运输：CHE-14和Dispatched参与胞吐作用，Patched和NPC1参与内吞作用。
