Palytoxin modulates cytosolic pH in human osteoblast-like Saos-2 cells via an interaction with Na(+)-K(+)-ATPase.
Palytoxin (PTx) at nanomolar concentrations enhances the permeability of mammalian cell membranes to both Na+ and Ca2+. In basal human osteoblast-like Saos-2 cells, PTx (8 nM) caused a persistent decrease in cytosolic pH (pHi) of about 0.2 units, which required the presence of extracellular Ca2+ (Cae2+) and Na+ (Nae+). We acidified Saos-2 cells by incubation with nigericin to examine the action of PTx in cells with an activated Na+/H+ antiporter. Under these conditions, PTx increased the pHi without requiring Cae2+ or Nae+, and the alkalinization was unaffected by hexamethylene amiloride. We conclude that the PTx-induced rise in pHi did not involve the Na+/H+ antiporter. PTx increased the rate of 86Rb+ efflux. We propose that PTx induced alkalinization in nigericin-acidified cells by collapsing the K+ gradient. Exposure to ouabain had no effect on pHi, but it prevented the actions of PTx on PHi in both basal and nigericin-acidified cells. Ouabain-resistant mutant cells were less sensitive to PTx in extruding 86Rb+ than their ouabain-sensitive parents. We conclude that PTx interacts with the Na(+)-K(+)-adenosinetriphosphatase to regulate pHi in both basal and nigericin-acidified Saos-2 cells.
Monroe
J J
JJ
Department of Molecular and Cellular Toxicology, Harvard School of Public Health, Boston, Massachusetts, USA.
Tashjian
A H
AH
D000178:Acrylamides / Q000494:pharmacology*; D002460:Cell Line; D003064:Cnidarian Venoms / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D004351:Drug Resistance; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D012413:Rubidium / Q000493:pharmacokinetics; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D000095702:Polyether Toxins
D000178:Acrylamides; D003064:Cnidarian Venoms; D010042:Ouabain; D012413:Rubidium; D000254:Sodium-Potassium-Exchanging ATPase; C010272:palytoxin; D000095702:Polyether Toxins