MODULATION OF ALPHA-5-BETA-1 AND ALPHA-V-BETA-3 INTEGRINS ON THE CELL-SURFACE DURING MITOSIS

One of the hallmarks of cells undergoing mitotic division is their rou nded morphology and reduced adhesion to the substratum. We have studie d and compared the attachment of interphase and mitotic cells to subst rata coated with fibronectin and vitronectin. We have found that adhes ion of mitotic cells, as compared to interphase cells, is significantl y reduced to fibronectin, but is higher to vitronectin. These results correlate well with the expression of alpha 5 beta 1 and alpha V beta 3 integrins, the respective receptors for fibronectin and vitronectin, on the cell surface. Mitotic cells show higher levels of alpha V beta 3 and very low levels of alpha 5 beta 1 proteins on the cell surface as compared to interphase cells. This difference in the levels of thes e integrins also reflects in the total amounts of fibronectin and vitr onectin present on the cell surface of these cells. We have further sh own, by flow cytometry, that binding of vitronectin, or the synthetic peptide -GRGDSP-, causes an increase in the intracellular levels of Ca 2+ in mitotic cells, but no change is seen in the interphase cells. Bi nding of fibronectin to either of these cells fails to elicit any resp onse. One interesting feature of our results is that the levels of tot al, i.e., cytoplasmic plus membrane bound, alpha 5 beta 1 and alpha V beta 3 integrins of mitotic and interphase cells remain the same, thus implying an alteration in the distribution of integrin chains between the plasma membrane and the cytoplasm during the conversion of interp hase cells into the mitotic phase. (C) 1996 Wiley-Liss, Inc.