Department of Cell Biology, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205-2196, USA.
Development. 2014 May;141(9):1950-60. doi: 10.1242/dev.104166. Epub 2014 Apr 9.
Apical and basolateral determinants specify and maintain membrane domains in epithelia. Here, we identify new roles for two apical surface proteins - Cadherin 99C (Cad99C) and Stranded at Second (SAS) - in conferring apical character in Drosophila tubular epithelia. Cad99C, the Drosophila ortholog of human Usher protocadherin PCDH15, is expressed in several embryonic tubular epithelial structures. Through loss-of-function and overexpression studies, we show that Cad99C is required to regulate cell rearrangement during salivary tube elongation. We further show that overexpression of either Cad99C or SAS causes a dramatic increase in apical membrane at the expense of other membrane domains, and that both proteins can do this independently of each other and independently of mislocalization of the apical determinant Crumbs (Crb). Overexpression of Cad99C or SAS results in similar, but distinct effects, suggesting both shared and unique roles for these proteins in conferring apical identity.
顶端和基底侧决定因素指定并维持上皮细胞的膜域。在这里，我们确定了两个顶端表面蛋白 - Cadherin 99C（Cad99C）和 Stranded at Second（SAS） - 在赋予果蝇管状上皮细胞顶端特征方面的新作用。Cad99C 是人类 Usher 原钙粘蛋白 PCDH15 的果蝇同源物，在几种胚胎管状上皮结构中表达。通过功能丧失和过表达研究，我们表明 Cad99C 是在唾液管伸长过程中调节细胞重排所必需的。我们进一步表明，Cad99C 或 SAS 的过表达以牺牲其他膜域为代价导致顶端膜的急剧增加，并且这两种蛋白质可以彼此独立地并且独立于顶端决定因素 Crumbs（Crb）的定位错误来做到这一点。Cad99C 或 SAS 的过表达导致类似但不同的效果，这表明这些蛋白质在赋予顶端身份方面具有共同和独特的作用。
