Cytoskeletal rearrangement in K562 erythroleukaemic cells forced to grow on a positively charged polymer surface.
We have recently demonstrated that if human K562 erythroleukaemic cells, which normally grow in suspension, are grown on a positively-charged surface composed of polylysine, a transient reorganization of CD54 (ICAM-1), CD58 (LFA-3) and alphanubeta3 (vitronecin receptor), three important CAMs located on the cell membrane, takes place. In addition, changes of longer duration in membrane conductivity (ionic transport across the cell membrane) and membrane permittivity (static distribution of charges across the cell membrane), indicating more permanent structural as well as functional alterations in the cell membrane, were also observed [2]. Because of the close interrelationship which exists between the cell membrane, CAMs and the cytoskeleton, changes in this intracellular network as well as in the surface morphology of K562 cells grown on the positively-charged polymer, polylysine, were examined. In particular, actin and tubulin were investigated qualitatively and quantitatively by immunofluorescence microscopy and flow cytometry, respectively, while the cell surface was studied by scanning electron microscopy (SEM). The data indicate that when K562 cells are grown onto polylysine no quantitative changes occurred to the cytoskeletal elements even if these were rearranged and that the cell membrane surface is also greatly altered. These results are discussed in light of the pivotal role played by CAMs and the cell cytoskeleton in transducing environmental stimuli, in this case those provided by a positive charge, from the cell membrane to the inside of the cell.
Calcabrini
A
A
Laboratorio di Ultrastrutture, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
Rainaldi
G
G
Santini
M T
MT