Morphogenetic activity of extracellular matrices on cultured podocytes. Laminin accelerates podocyte process formation in vitro.

Morphogenetic effects of various extracellular matrix proteins on the renal podocyte were investigated using the conditionally immortalized podocyte cell line. Podocytes were plated on glass coverslips and coated with the following matrix proteins: laminin-10/11, laminin-1, fibronectin, collagen type IV, collagen type I. Three hours after plating, podocytes on laminins developed prominent processes, while those on other matrix proteins started to elongate processes after two days. Vinculin-immunolabeling showed that podocytes plated on laminins possessed thin rod-shaped focal contacts, whereas those on fibronectin showed large dot-shaped focal contacts. Inhibition of serine/threonine protein kinases induced podocyte process formation in an extracellular matrix-independent manner. The present study reveals the significance of laminin on podocyte morphogenesis in vitro, and shows that different extracellular matrix proteins trigger different intracellular signals governing podocyte morphogenesis. Taken together with our previous studies, podocyte process formation is thought to be regulated by protein Ser/Thr phosphorylation.