Wodarz A, Hinz U, Engelbert M, Knust E
Institut für Entwicklungsbiologie, Universität zu Köln, Federal Republic of Germany.
Cell. 1995 Jul 14;82(1):67-76. doi: 10.1016/0092-8674(95)90053-5.
The crumbs protein of Drosophila is an integral membrane protein, with 30 EGF-like and 4 laminin A G domain-like repeats in its extracellular segment, which is expressed on the apical plasma membrane of all ectodermally derived epithelia. Here, we present evidence to show that the insertion of crumbs into the plasma membrane is necessary and sufficient to confer apical character on a membrane domain. Overexpression of crumbs results in an enormous expansion of the apical plasma membrane and the concomitant reduction of the basolateral domain. This is followed by the redistribution of beta Heavy-spectrin, a component of the membrane cytoskeleton, and by the ectopic deposition of cuticle and other apical components into these areas. Strikingly, overexpression of the membrane-bound cytoplasmic portion of crumbs alone is sufficient to produce this dominant phenotype. Our results suggest that crumbs plays a key role in specifying the apical plasma membrane domain of ectodermal epithelial cells of Drosophila.
果蝇的面包屑蛋白是一种整合膜蛋白，其细胞外区域有30个表皮生长因子样重复序列和4个层粘连蛋白A G结构域样重复序列，在所有外胚层来源上皮的顶端质膜上表达。在此，我们提供证据表明，面包屑蛋白插入质膜对于赋予膜结构域顶端特征是必要且充分的。面包屑蛋白的过表达导致顶端质膜大量扩张，同时基底外侧结构域减少。随后，膜细胞骨架成分β重肌动蛋白发生重新分布，角质层和其他顶端成分异位沉积到这些区域。引人注目的是，仅过表达面包屑蛋白的膜结合细胞质部分就足以产生这种显性表型。我们的结果表明，面包屑蛋白在确定果蝇外胚层上皮细胞的顶端质膜结构域中起关键作用。
