Directed membrane transport is involved in process formation in cultured podocytes

Mature glomerular visceral epithelial cells, or podocytes, are unique cells with a complex cell architecture. Characteristically, they possess a highl y branched array of major processes and foot processes, which are essential for glomerular filtration in the kidney. A podocyte cell line with the pot ential to exhibit many features of differentiated podocytes, particularly t he formation of cell processes, was recently established. In this study, it is shown that directed membrane transport is involved in process formation in cultured podocytes. The well-characterized vesicular stomatitis virus G was used as a marker protein for the biosynthetic pathway in these cells. It seems that newly synthesized vesicular stomatitis virus G is preferentia lly delivered into the cell processes of the podocytes. where it is colocal ized with known regulators of vesicular transport from the Golgi apparatus to the plasma membrane, such as the small GTPase rab8 and the sec6/sec8 com plex. To determine the rule of vesicular transport in process formation, ce lls were treated with brefeldin A, a drug that disrupts the trafficking of post-Golgi transport vesicles. As a result, the podocytes reversibly lost t heir ability to form processes. These findings suggest that podocytes are d ependent on a constant fresh source of lipids and proteins to form their pr ocesses.