Contribution of the cytoskeleton and the phospholipase C signaling pathway to fluid stream-induced membrane currents.
A fluid stream induced by a concentration clamp system evokes in Xenopus oocytes a deformation of the membrane which results in transient chloride currents of high amplitude (stream-evoked inward current, I(i,st)) during calcium-activated chloride current oscillations. The involvement of cytoskeleton elements and of components of the phospholipase C-dependent signaling pathway on the generation of the I(i,st) were investigated. Incubation of the oocytes with cytoskeleton-disrupting agents exerted no effects on generation of the I(i,st), suggesting that the mechanotransduction is not mediated by these structures. The fluid stream induced an elevation of the submembraneous calcium concentration, as measured by an increase of Fluo-4-mediated fluorescence after the stimulus. Lowering the intracellular calcium concentration by injection of calcium chelators or depleting inositol 1,4,5-triphosphate (InsP(3))-sensitive calcium stores by blockers of the calcium pumps suppressed the generation of the I(i,st) in most cases. Furthermore, the phospholipase C inhibitor U73122 reversibly blocked the I(i,st). The results suggest that the fluid stream leads to a membrane stretch which modulates directly or indirectly the activity of a membrane-bound phospholipase C. The phospholipase C transiently elevates the InsP(3) concentration, in turn releasing calcium from InsP(3)-sensitive internal calcium stores, thus evoking an enhanced calcium-sensitive chloride current.
Montag
Sebastian
S
Department of Medicine, Institute of Physiology, University of Muenster, Robert-Koch-Str. 27a, 48149 Muenster, Germany.
Krüger
Katharina
K
Madeja
Michael
M
Speckmann
Erwin-Josef
EJ
Musshoff
Ulrich
U
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology; D002614:Chelating Agents / Q000494:pharmacology; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology; D003599:Cytoskeleton / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007424:Intracellular Fluid / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002614:Chelating Agents; D018118:Chloride Channels; D004791:Enzyme Inhibitors; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D002118:Calcium