Binding of the renal epithelial cell line LLC-PK1 to laminin is regulated by protein kinase C

The alpha 6 beta 1 integrin heterodimer has been implicated in the mediatio n of renal epithelial cell binding to laminin, and it has been suggested th at this binding is important for renal morphogenesis and development. Studi es of nonrenal cells have suggested that the functional activity of alpha 6 beta 1 integrin is regulated by protein kinase C (PKC) activity. In this s tudy, the binding of a renal epithelial cell line, LLC-PK1, to laminin was characterized and the role of PKC activity in the modulation of binding was investigated. LLC-PK1 cells bound to laminin-coated surfaces in a time- an d laminin concentration-dependent manner. Binding was strongly inhibited by anti-beta 1 integrin antibodies and by anti-alpha 6 integrin antibodies. A ntibodies against alpha 2 integrin and alpha 3 integrin had little inhibito ry effect. Cells bound to both whole laminin and laminin fragment E8, i.e., the fragment to which the alpha 6 beta 1 integrin heterodimer binds. Expos ure of cells to PKC activators for as little as 2 h enhanced cell binding t o laminin approximately twofold, in a protein synthesis-dependent manner. P KC inhibitors antagonized this effect. PKC-stimulated binding was also inhi bited by anti-beta 1 integrin and anti-alpha 6 integrin antibodies. PKC act ivation did not alter expression of beta 1 integrin subunits at the cell su rface after short time periods (2 to 4 h), but expression was increased aft er longer time periods (24 h). These results indicate that the renal epithe lial cell line LLC-PK1 binds to laminin via the alpha 6 beta 1 integrin het erodimer and binding is enhanced by PKC activation. The PKC-mediated enhanc ement of binding requires protein synthesis and is mediated in part by acti vation of surface alpha 6 beta 1 integrin.