Control of Polarized Basement Membrane Secretion in Epithelial Cells - The development and normal physiology of multicellular organisms relies on the presence and proper function of epithelial tissue. Epithelia are characterized by their organization as sheets of tightly adherent cells that are polarized along an apical-basal axis. The cellular basis to accomplish their functions is provided by their polarized architecture. Loss of this organization has significant detrimental consequences, such as developmental defects and cancer. The basement membrane (BM), a specialized sheet of the extracellular matrix, is secreted basally by epithelial cells and is a major regulator of epithelial polarity, tissue organization, and organ morphogenesis. Importantly, the loss of integrity and misregulation of the BM have been associated with a broad range of diseases including stroke, cerebrovascular and kidney diseases, and tumor metastasis. Despite the significance of the BM in both normal and abnormal epithelial cells, the molecular mechanisms ensuring the accurate basal secretion of BM proteins remain largely elusive. The main goals of this work are to discover new components, determine their precise roles, and organize them into biological pathway(s) dedicated to the establishment and maintenance of BM polarity. To study polarized BM deposition, we are using the follicular epithelium of the Drosophila ovary as a model system. Using the power of Drosophila genetics, along with established cellular, biochemistry, and advanced imaging techniques, our lab composed of undergraduate and graduate students will characterize the role of different genes that we recently identified as critical for the proper placement of BM proteins. In Aim 1, we will determine the roles of the SNAREs, recently identified in a genetic screen performed by undergraduate students, in the polarized intracellular trafficking and secretion of BM proteins. In parallel, our lab will also characterize the role of Crag’s partners, a key regulator of BM polarity, in this process. In Aim 2, we will investigate the role of the G-protein-coupled receptor (GPCR) signaling pathway in BM polarity. To monitor the intracellular trafficking of BM-containing vesicles that leads to the basal deposition of BM protein, undergraduate and graduate students will visualize and measure it, both in fixed tissue as well as live imaging, using confocal, super-resolution, and electron microscopy. Altogether, this scientific proposal will provide critical insights into the biological pathways involved in the control of BM polarity, and by extension on our understanding of the development and maintenance of epithelial cell polarity, and its deregulation in pathological situations such as cancer. Furthermore, this proposal will continue to provide high-impact biomedical research experience to undergraduate students.
