HGF-mediated chemotaxis and tubulogenesis require activation of the phosphatidylinositol 3-kinase

Abstract

The association of hepatocyte growth factor (HGF) with its high-affinity receptor, c-met, has been shown to induce mitogenesis, motogenesis, and morphogenesis in renal epithelial cells (L. G. Cantley, E. J. G. Barros, M. Gandhi, M. Rauchman, and S. K. Nigam. Am. J. Physiol. 267 (Renal Fluid Electrolyte Physiol. 36): F271-F280, 1994), suggesting that HGF may be critical to the orchestration of both renal development and regeneration following injury. Although signal transduction pathways activated by c-met include the phosphatidylinositol 3-kinase (PI-3-kinase), phospholipase C gamma, ras, and others, the activation of PI-3-kinase has been the most striking in vivo. We therefore investigated whether the pathways that mediate phenotypic changes in inner medullary collecting duct cells are altered by inhibition of PI-3-kinase with the fungal metabolite, wortmannin. In these cells, the mean inhibitory concentration for in vitro wortmannin inhibition of PI-3-kinase was approximately 0.2 nM. At this low concentration, motogenesis (quantified by chemotaxis) and morphogenesis (by branching-process formation within collagen matrix) were inhibited in a striking and parallel fashion, while mitogenesis was inhibited to a lesser degree. These experiments suggest that activation of PI-3-kinase is critical for c-met-mediated chemotaxis and tubulogenesis.

An in vitro tubulogenesis system using cell lines derived from the embryonic kidney shows dependence on multiple soluble growth factors

“…1, UB cells were cytokeratin-positive, Ecadherin-positive, ZO-1-positive, and partially (5-30%, depending on passage) vimentin-positive, consistent with an epithelial character as previously described (25). In contrast, BSN cells (passage [4][5][6][7][8][9][10][11][12][13][14] were negative for cytokeratin, though strongly positive for vimentin, consistent with a mesenchymal character. No cell surface staining for E-cadherin or ZO-1 was observed, though some faint cytoplasmic staining of ZO-1, which has been reported for a number of mesenchymal cell lines (31), was observed.…”

“…Systems for branching tubulogenesis that have been employed previously utilize cell lines such as MDCK or mIMCD3 derived from the mature kidney (10)(11)(12)(13)(14)(15)(16)36). In these cell lines, the major factors capable of inducing early cellular process formation leading to branching tubulogenesis appear to be HGF and EGFR ligands (e.g., EGF, TGF-␣, heparin-binding EGF, amphiregulin, betacellulin) (10,11).…”

“…To the extent that this kind of approach reflects events occurring in vivo during development, it can be used to gain mechanistic insights into complex morphogenetic processes. One of the best-studied models employs kidney epithelial cell lines, such as Madin-Darby canine kidney (MDCK) and murine inner medullary collecting duct (mIMCD3), seeded in three-dimensional type I collagen gels to analyze mechanisms of epithelial tubulogenesis and branching morphogenesis (10)(11)(12)(13)(14)(15)(16)(17). In the mIMCD3 cellcollagen gel system, HGF and EGFR ligands induce branching tubulogenesis (10,11), whereas transforming growth factor (TGF)-␤ selectively inhibits branching events (14).…”

Differential phosphorylation of the docking protein Gab1 by c-Src and the hepatocyte growth factor receptor regulates different aspects of cell functions

“…On the other hand, phosphorylation of Gab1 by HGF receptor may allow Gab1 to bind to SHP2 and/or PI3K, which then contributes to HGFinduced cell motility (Figure 9b). Accordingly, Crk has been shown to enhance HGF-induced mitogenesis (Riordan et al, 2000), whereas PI3K has been shown to be important for HGF-induced chemotaxis (Derman et al, 1995;Machide et al, 2000).…”

Enhancement of in vitro human tubulogenesis by endothelial cell-derived factors: implications for in vivo tubular regeneration after injury

“…Using this model, various factors have been discovered to be involved in branching tubulogenesis. Murine inner medullary collecting duct (IMCD)-3 cells (1,5,7,26) or rat primary tubular cells (4) are also utilized for the study of tubulogenesis. These in vitro models, in which HGF has been shown to induce tubular formation, are well defined, practical, and contribute to an understanding of the mechanism of tubulogenesis.…”