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- Title
Palytoxin Acts on Na<sup>+</sup>,K<sup>+</sup>-ATPase but not Nongastric H<sup>+</sup>,K<sup>+</sup>-ATPase.
- Authors
Guennoun-Lehmann, Saida; Fonseca, James E.; Horisberger, Jean-Daniel; Rakowski, Robert F.
- Abstract
Palytoxin (PTX) opens a pathway for ions to pass through Na,K-ATPase. We investigate here whether PTX also acts on nongastric H,K-ATPases. The following combinations of cRNA were expressed in Xenopus laevis oocytes: Bufo marinus bladder H,K-ATPase α2- and Na,K-ATPase β2-subunits; Bufo Na,K-ATPase α1- and Na,K-ATPase β2-subunits; and Bufo Na,K-ATPase β2-subunit alone. The response to PTX was measured after blocking endogenous Xenopus Na,K-ATPase with 10 μ m ouabain. Functional expression was confirmed by measuring 86Rb uptake. PTX (5 n m) produced a large increase of membrane conductance in oocytes expressing Bufo Na,K-ATPase, but no significant increase occurred in oocytes expressing Bufo H,K-ATPase or in those injected with Bufo β2-subunit alone. Expression of the following combinations of cDNA was investigated in HeLa cells: rat colonic H,K-ATPase α1-subunit and Na,K-ATPase β1-subunit; rat Na,K-ATPase α2-subunit and Na,K-ATPase β2-subunit; and rat Na,K-ATPase β1- or Na,K-ATPase β2-subunit alone. Measurement of increases in 86Rb uptake confirmed that both rat Na,K and H,K pumps were functional in HeLa cells expressing rat colonic HKα1/NKβ1 and NKα2/NKβ2. Whole-cell patch-clamp measurements in HeLa cells expressing rat colonic HKα1/NKβ1 exposed to 100 n m PTX showed no significant increase of membrane current, and there was no membrane conductance increase in HeLa cells transfected with rat NKβ1- or rat NKβ2-subunit alone. However, in HeLa cells expressing rat NKα2/NKβ2, outward current was observed after pump activation by 20 m m K+ and a large membrane conductance increase occurred after 100 n m PTX. We conclude that nongastric H,K-ATPases are not sensitive to PTX when expressed in these cells, whereas PTX does act on Na,K-ATPase.
- Publication
Journal of Membrane Biology, 2007, Vol 216, Issue 2/3, p107
- ISSN
0022-2631
- Publication type
Academic Journal
- DOI
10.1007/s00232-007-9040-1