The impact of intracellular membrane-associated Crumbs mobility for cell polarity, cell contacts and signal transduction in renal epithelial cells.

点击翻译按钮获取中文摘要

The mammalian kidney contains 1 to 2 million nephrons, which are considered as the smallest physiological subunits. Although kidney epithelia of the nephron are functionally and morphologically very divergent, they all display a distinct cell polarization and form cell-cell contacts. Both cell polarity and cell contact formation are dependent on the asymmetric distribution of the Crumbs (or the Crumbs protein network) within the plasma membrane. However, so far only little is known about how this Crumbs asymmetry is realized and maintained on a molecular level. In the kidney, the Crumbs proteins Crb2, Crb3A and Crb3B are expressed. In preliminary studies we showed that Crb3A and Crb3B differ in their lateral mobility within the plasma membrane. Also vesicles loaded with either Crb3A or Crb3B exhibit different mobility patterns. Crb3B-positive vesicles appeared generally more mobile and were less often immobilized compared to Crb3A vesicles.We assume that the mobility pattern within respectively towards the plasma membrane is important to achieve and maintain asymmetrically organized membranes in the kidney. On the other hand perturbations of the mobility or directed Crumbs movement could disrupt renal cell-cell contacts, e.g. in the slit diaphragm. This is especially important since it has recently been shown that certain mutations in the human CRB2 gene can come along with a disruption of the glomerular filtration barrier. Crb3A and Crb3B are expressed in all renal epithelia, but Crb2 preferentially in podocytes. Thus, we intend to analyze the mobility patterns of Crb2, Crb3A and Crb3B in podocyte cell membranes as well as in MDCK cell membranes, which represent cellular models for tubular apical epithelial membranes. In this manner the role of Crumbs mobility for influencing cell polarity, cell cell contacts, actin dynamics and signaling processes in renal cells shall be elucidated. In our cooperation project we will combine for the first time cell biological approaches with quantitative light microscopy techniques (single molecule/particle tracking and fluorescence photobleaching measurements) to uncover the movement of key molecules like Crb2 on the renal plasma membrane.