Journal
AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY
Volume 285, Issue 5, Pages C1270-C1280Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpcell.00153.2003
Keywords
calcium puffs; gastrointestinal smooth muscle; colonic motility
Categories
Funding
- NIDDK NIH HHS [DK 41315] Funding Source: Medline
- NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES [P01DK041315] Funding Source: NIH RePORTER
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Colonic myocytes have spontaneous, localized, Ins (1,4,5) trisphosphate (IP3) receptor-dependent Ca2+ transients that couple to the activation of Ca2+-dependent K+ channels and spontaneous transient outward currents (STOCs). We previously reported that the coupling strength between spontaneous Ca2+ transients and large conductance Ca2+ activated K+ (BK) channels is regulated by Ca2+ influx through nonselective cation channels and activation of protein kinase C (PKC). Here, we used confocal microscopy and the patch-clamp technique to further investigate the coupling between localized Ca2+ transients and STOCs in colonic myocytes from animals lacking the regulatory beta(1)-subunit of BK channels. Myocytes from beta(1)-knockout (beta(1)(-/-)) animals loaded with fluo 4 showed typical localized Ca2+ transients, but the STOCs coupled to these events were of abnormally low amplitude. Reduction in external Ca2+ or application of inhibitors of nonselective cation channels (SKF-96365) caused no significant change in the amplitude or frequency of STOCs. Likewise, an inhibitor of PKC, GF 109203X, had no significant effect on STOCs. Single-channel recording from BK channels showed that application of an activator (PMA) and an inhibitor (GF 109203X) of PKC did not affect BK channel openings in myocytes of beta(1)(-/-) mice. These data show that PKC-dependent regulation of coupling strength between Ca2+ transients and STOCs in colonic myocytes depends upon the interaction between alpha- and beta(1)-subunits.
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