Transformation of renal tubule epithelial cells by simian virus-40 is associated with emergence of Ca(2+)-insensitive K+ channels and altered mitogenic sensitivity to K+ channel blockers.
We compared the pattern of K+ channels and the mitogenic sensitivity to K+ channel blocking agents in primary cultures of rabbit proximal tubule cells (PC.RC) (Ronco et al., 1990) and two derived SV-40-transformed cell lines exhibiting specific functions of proximal (RC.SV1) and more distal (RC.SV2) tubule cells (Vandewalle et al., 1989). First, K+ channel equipment surveyed by the patch-clamp technique was modified after SV-40 transformation in both cell lines; although a high conductance Ca(2+)-activated K+ channel [K+200 (Ca2+)] remained the most frequently recorded K+ channel, the transformed state was characterized by emergence of three Ca(2+)-insensitive K+ channels (150, 50, and 30 pS), virtually absent from primary culture, contrasting with reduced frequency of two Ca(2+)-sensitive K+ channels (80 and 40 pS). Second, quinine (Q), tetraethylammonium ion (TEA) and charybdotoxin (CTX), at concentrations not affecting cell viability, all decreased 3H-TdR incorporation and cell growth in PC.RC cultures, but only TEA had similar effects in transformed cells. The latter were further characterized by paradoxical effects of Q that induced a marked increase in thymidine incorporation. Q also exerted contrasting effects on channel activity: it inhibited the [K+200 (Ca2+)] when the channel was highly active, with a Ki (0.2 mM) similar to that measured for 3H-TdR incorporation in PC.RC cells (0.3 mM), but increased the mean current through poorly active channels. TEA blocked all K+ channels with conductance greater than or equal to 50 pS, including the [K+200 (Ca2+)], in a range of concentrations that substantially affected cell proliferation. The unique effect of TEA on SV-40-transformed cells might be related to broad inhibition of K+ channels.
Teulon
J
J
INSERM U.323, Faculté de Médecine Necker-Enfants-Malades, Paris, France.
Ronco
P M
PM
Geniteau-Legendre
M
M
Baudouin
B
B
Estrade
S
S
Cassingena
R
R
Vandewalle
A
A
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral / Q000187:drug effects; D002478:Cells, Cultured; D018999:Charybdotoxin; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004342:Drug Hypersensitivity; D004847:Epithelial Cells; D004848:Epithelium / Q000502:physiology / Q000648:ultrastructure; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000502:physiology / Q000648:ultrastructure; D008934:Mitogens / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011803:Quinine / Q000494:pharmacology; D011817:Rabbits; D012604:Scorpion Venoms / Q000494:pharmacology; D013539:Simian virus 40 / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D014316:Tritium
D008934:Mitogens; D015221:Potassium Channels; D012604:Scorpion Venoms; D013757:Tetraethylammonium Compounds; D014316:Tritium; D018999:Charybdotoxin; D004247:DNA; D011803:Quinine; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium; D013936:Thymidine