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Leptin activation of ATP‐sensitive K + (K ATP ) channels in rat CRI‐G1 insulinoma cells involves disruption of the actin cytoskeleton
Author(s) -
Harvey J.,
Hardy S. C.,
Irving A. J.,
Ashford M. L. J.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00095.x
Subject(s) - phalloidin , cytochalasin b , nocodazole , cytoskeleton , actin , microbiology and biotechnology , biology , biophysics , chemistry , biochemistry , cell
1 The role of the cytoskeleton in leptin‐induced activation of ATP‐sensitive K + (K ATP ) channels was examined in rat CRI‐G1 insulin‐secreting cells using patch clamp and fluorescence imaging techniques. 2 In whole cell recordings, dialysis with the actin filament stabiliser phalloidin (10 μ m ) prevented K ATP channel activation by leptin. 3 Application of the actin filament destabilising agents deoxyribonuclease type 1 (DNase 1; 50 μg ml −1 ) or cytochalasin B (10 μ m ) to intact cells or inside‐out membrane patches also increased K ATP channel activity in a phalloidin‐dependent manner. 4 The anti‐microtubule agents nocodazole (10 μ m ) and colchicine (100 μ m ) had no effect on K ATP channel activity. 5 Fluorescence staining of the cells with rhodamine‐conjugated phalloidin revealed rapid disassembly of actin filaments by cytochalasin B and leptin, the latter action being prevented by the phosphoinositide 3 (PI 3)‐kinase inhibitor LY 294002. 6 Activation of K ATP channels by the PI 3‐kinase product phosphatidylinositol 3,4,5‐trisphosphate (PtdIns(3,4,5) P 3 ) was also prevented by phalloidin. This is consistent with the notion that leptin activates K ATP channels in these cells by an increase in PtdIns(3,4,5) P 3 or a similar 3‐phosphorylated phosphoinositol lipid, resulting in actin filament disruption.