Positively charged polymer polylysine-induced cell adhesion molecule redistribution in K562 cells

We have recently demonstrated that if human K562 erythroleukemic cells, whi ch normally grow in suspension, are grown in polylysine-coated culture flas ks for 48 h, they adhere to these flasks and grow in an anchorage-dependent like manner. Important changes in both membrane conductivity (ionic transp ort across the cell membrane) and membrane permittivity (static distributio n of charges across the cell membrane) were also observed, indicating pertu rbations in membrane lipids, proteins and polysaccharides. In order to bett er understand the changes occurring in K562 cells exposed to polylysine and because of the important role played by cell adhesion molecules (CAMs) in cell/cell and cell/substratum interactions, and in cellular adaptation to t he surrounding environment, the possible redistribution of these molecules after exposure to polylysine were investigated. In particular, the CD54 (IC AM-1), CD58 (LFA-3) and alpha(v)beta(3) (vitronectin receptor) molecules we re investigated at different times of growth both quantitatively and qualit atively utilizing flow cytometry and immunofluorescence microscopy, respect ively. The data indicate that there were no significant quantitative variat ions in the CAMs examined at all the times tested. In addition, no qualitat ive changes were observed at 48 h (as well as 24 h) of exposure. However, s horter treatment times (30 min, 1 and 2 h) did induce important CAM reorgan ization. The results seem to demonstrate that this cycle of CAM redistribut ion may, in part, be responsible for cellular adaptation to the new growth environment of K562 cells and for the variations in membrane electrical pro perties observed. (C) 1998 Kluwer Academic Publishers.