Szul Tomasz, Burgess Jason, Jeon Mili, Zinn Kai, Marques Guillermo, Brill Julie A, Sztul Elizabeth
Department of Cell Biology; University of Alabama at Birmingham; Birmingham, AL USA.
Cell Logist. 2011 Mar;1(2):69-76. doi: 10.4161/cl.1.2.15512.
Surface delivery of proteins involved in cell-cell and cell-matrix interactions in cultured mammalian cells requires the GBF1 guanine nucleotide exchange factor. However, the role of GBF1 in delivery of adhesion proteins during organogenesis in intact animals has not been characterized. Here, we report the function of the fly GBF1 homolog, Gartenzwerg (Garz) in the development of the salivary gland in Drosophila melanogaster. We used the GAL4/UAS system to selectively deplete Garz from salivary gland cells. We show that depletion of Garz disrupts the secretory pathway as evidenced by the collapse of Golgi-localized Lava lamp (Lva) and the TGN-localized γ subunit of the clathrin-adaptor protein complex (AP-1). Additionally, Garz depletion inhibits trafficking of cell-cell adhesion proteins cadherin (DE-cad) and Flamingo to the cell surface. Disregulation of trafficking correlates with mistargeting of the tumor suppressor protein Discs large involved in epithelial polarity determination. Garz-depleted salivary cells are smaller and lack well-defined plasma membrane domains. Garz depletion also inhibits normal elongation and positioning of epithelial cells, resulting in a disorganized salivary gland that lacks a well defined luminal duct. Our findings suggest that Garz is essential for establishment of epithelial structures and demonstrate an absolute requirement for Garz during Drosophila development.
在培养的哺乳动物细胞中，参与细胞间和细胞与基质相互作用的蛋白质的表面递送需要GBF1鸟嘌呤核苷酸交换因子。然而，GBF1在完整动物器官发生过程中粘附蛋白递送中的作用尚未得到明确。在这里，我们报道了果蝇GBF1同源物Gartenzwerg（Garz）在黑腹果蝇唾液腺发育中的功能。我们使用GAL4/UAS系统从唾液腺细胞中选择性地消耗Garz。我们发现，Garz的消耗破坏了分泌途径，这可通过高尔基体定位的Lava lamp（Lva）和网格蛋白衔接蛋白复合物（AP-1）的TGN定位的γ亚基的崩溃来证明。此外，Garz的消耗抑制了细胞间粘附蛋白钙粘蛋白（DE-cad）和Flamingo向细胞表面的运输。运输失调与参与上皮极性确定的肿瘤抑制蛋白Discs large的错误靶向相关。Garz耗尽的唾液细胞较小，并且缺乏明确的质膜结构域。Garz的消耗还抑制上皮细胞的正常伸长和定位，导致唾液腺紊乱，缺乏明确的管腔导管。我们的研究结果表明，Garz对于上皮结构的建立至关重要，并证明了果蝇发育过程中对Garz的绝对需求。
