Role of alpha 3 beta 1 integrin in tubulogenesis of Madin-Darby canine kidney cells

Background. We isolated several Madin-Darby canine kidney: (MDCK) subclones that exhibit different degrees of branching tubulogenesis in lower concent rations of collagen gel. The M634 clone formed cell aggregates in 0.3% coll agen gel, but developed branching tubules vigorously in 0.1% collagen gel. In contrast, the Y224 clone formed cysts in 0.3% collagen gel and displayed fewer branching structures in 0.1% collagen eel. Morphologically, M634 cel ls exhibited higher levels of cell scattering as well as collagen-induced c ell migration than Y224. We conducted this study to delineate the underlyin g mechanism of branching tubulogenesis in M634 cells. Methods. Components of the focal contact machinery were analyzed in both ce ll lines, including the extracellular matrix glycoproteins fibronectin, lam inin, and vitronectin; cytoskeleton-associated elements a-actinin. talin, a nd vinculin: and receptors for extracellular matrix and alpha (2), alpha (3 ), alpha (5), alpha (8), beta (1), and beta (3) integrins. Furthermore, we established several stable transfectants of alpha (3) integrin antisense RN A in M634 cells to examine the role of alpha (3)beta (1), integrin in branc hing morphogenesis directly;. Results. There were no obvious differences in levels of the focal adhesion complex proteins between M634 and Y224 cells, except that the content of th e alpha (3) and beta (1) integrins were 1.2- and 0.6-fold higher in M634 ce lls, respectively. The expression of alpha (3) integrin antisense RNA signi ficantly lowered the levels of alpha (3) integrin mRNA and protein. The pot ential of cell scattering, migration, and branching tubulogenesis in M634 c ells was inhibited according to the decrease in alpha (3) integrin expressi on. Conclusion. Our data indicate that expression of alpha (3)beta (1) integrin regulates cell scattering. migration, and branching tubulogenesis of RIDGE ; cells. possibly via adhesion to or serving as a signaling molecule for ty pe I collagen.