Modulation of a volume-regulated chloride current by F-actin.
We have examined whether F-actin integrity is involved in activation of a volume-regulated Cl- current (VRChlC) in B-lymphocytes. VRChlC activation was initiated in response to establishing a whole cell recording in the presence of a hyposmotic gradient. Parallel confocal microscopy experiments using Rhodamine-Phalloidin (R-P) as a specific marker of F-actin showed that the submembrane actin ring is reversibly disrupted in response to an hyposmotic gradient. Disruptions of cortical F-actin integrity by 50 microM cytochalasin B (CB) does not trigger activation of VRChlC under isosmotic conditions or potentiate the rate of activation when the osmolarity of the extracellular solution was decreased by 75%. However, incubation with CB increased the rate of VRChlC activation in response to a 90% hyposmotic gradient. Phalloidin, a stabilizer of F-actin, decreases the rate of VRChlC activation in response to a 90% gradient, but has no effect in response to a 75% gradient. These observations suggest that disassembly of cortical F-actin is not critical for VRChlC activation in B-lymphocytes. The integrity of cortical F-actin, however, can exert a modulatory effect on the rate of VRChlC activation in the presence of a hyposmotic gradient.
Levitan
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Department of Physiology, Medical College of Pennsylvania, Philadelphia 19129, USA.
Almonte
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Mollard
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Garber
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D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D001402:B-Lymphocytes / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D003571:Cytochalasin B / Q000494:pharmacology; D006801:Humans; D017136:Ion Transport; D018613:Microscopy, Confocal; D009997:Osmotic Pressure; D010590:Phalloidine / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000199:Actins; D002712:Chlorides; D010590:Phalloidine; D003571:Cytochalasin B