We have characterized the integrins present on cultured tubule epithelial cells from human renal cortexes, enriched for proximal cells, using fluorescence microscopy, immunoprecipitation, and cell adhesion assays. By immunofluorescence, the α3-integrin subunit stained most intensely and was present on all cells predominantly at cell-cell contacts. The α6-subunit was present on all cells in a pattern consistent with extracellular matrix contacts. The α5-subunit was present on most cells in a cell-matrix contact pattern; α(V)-subunit was weakly positive and occasionally seen in cell- matrix contacts. The α2-subunit was present on clusters of distal tubule cells, predominantly at cell-cell contacts. Immunoprecipitation revealed the predominant integrin to be α3β1 with some α2β1, presumably contributed by distal cells. The α5β1-, α6β1-, α6β4-, and α(V)β3-integrins, as well as trace amounts of α1β1-integrins, were also present. The α4β1-integrin was not detected. Initial attachment to fibronectin was mediated by α(V)β3- and α5β1-integrins; initial attachment to laminin was mediated by the α6β1- and α3β1-integrins and, in some preparations, by an unidentified integrin; and initial attachment to collagen type IV was mediated by α(V)β3-integrin and an unidentified β1-integrin. After extensively immunodepleting membrane extracts with anti-α1, -α2, -α3, -α4, -α5, -α6, and -α(V) antibodies, an anti-β1 antibody still precipitated an integrin. Its electrophoretic mobility differs from the laminin-binding α7β1-integrin. Thus we have identified many of the integrins on cortical tubule cells and their role in mediating initial attachment to extracellular matrix. However, the cell adhesion assays and immunoprecipitations suggest the presence of an unidentified β1-integrin that may mediate renal tubule cell attachment to laminin and collagen.
|Journal||American Journal of Physiology - Renal Fluid and Electrolyte Physiology|
|Issue number||4 36-4|
|State||Published - 1994|
- extracellular matrix
- kidney tubules