Calcium-mediated modulation of microtubule assembly in human breast epithelial cells.
Normal human breast epithelial cells obtained from a reduction mammoplasty (S130) have been maintained in culture for up to a year in Ham's F12:Dulbecco's medium, with 5% equine serum and a low calcium concentration (0.04 mM). These cells undergo senescence and terminal differentiation if they are switched to high Ca2+ medium (1.05 mM). To clarify the mechanism by which Ca2+ regulates the growth of these cells, we studied the role of tubulin assembly-disassembly and the morphologic changes subsequent to high Ca2+ switch. An early Passage (9) of S130 breast epithelial cells growing in low Ca2+ medium was analyzed. Of a total of 785 counted cells, 720 (92%) were rounded and 65 (8%) were flat, elongated, and fibroblastlike. When the cells were switched to high Ca2+ medium, out of 553 cells, only 111 (20%) were rounded and the remaining 442 (80%) were elongated and fibroblastlike. Immunocytochemical localization of tubulin, using the immunogold silver enhancement technique, showed that the majority of low Ca2(+)-grown cells did not display a network of tubulin fibers, whereas high Ca2(+)-grown cells revealed extensive cytoplasmic network of polymerized tubulin, which seemed to stretch out the cells. Experiments designed to determine the mechanisms of tubulin polymerization in these cells revealed that: a) Cells grown in high Ca2+ medium containing 0.1 mM colchicine had a reduced proportion of elongated cells; b) treatment of the cells with the calcium ionophore A23187 in low calcium medium resulted in an increase in the number of elongated cells which had more polymerized tubulin; and d) treatment of the cells with cyclic-AMP in low Ca2+ medium had no observable effect on cell morphology. These results indicate that high levels of Ca2+ either favor tubulin polymerization or stabilize the polymerized state.
Ochieng
J
J
Department of Pathology, Michigan Cancer Foundation, Detroit 48201.
Tait
L
L
Russo
J
J
D001940:Breast / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D003994:Bucladesine / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D003078:Colchicine / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D014404:Tubulin / Q000378:metabolism
D014404:Tubulin; D000001:Calcimycin; D003994:Bucladesine; D000242:Cyclic AMP; D003078:Colchicine; D002118:Calcium