Activation of kca channels in airway smooth muscle cells by endogenous protein kinase a. Wang, Zhao-Wen, and Michael I. Kotlikoff. Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104
APStracts 3:0038L, 1996.
The regulation of calcium-activated potassium (KCa ) channels by endogenous protein kinase A was examined in inside-out patches from equine tracheal myocytes. In the absence of exogenous protein kinases, ATP (500 [mu]M) significantly augmented KCa channel activity when applied to the cytosolic patch surface; open-state probability (nPo, mean +/- SE) increased from 0.010 +/- 0.001 to 0.034 +/- 0.005 (n = 24). The stimulatory effect of ATP was mimicked by ATP-[delta]-S but not by AMP-PNP. Rather, AMP-PNP significantly inhibited channel activity. The protein kinase A (PKA) inhibitory peptide (PKI) significantly reduced nPo, and prevented the augmenting effect of subsequent ATP. Ht 31, an inhibitory peptide for A-kinase anchoring proteins (AKAPs), but not its proline-substituted mutant, also blocked the stimulatory effect of ATP. These results suggest that: 1) ATP augments KCa channel activity through phosphorylation; 2) the phosphorylation is catalyzed by endogenous PKA; 3) anchoring via AKAP is required to maintain association of PKA with the membrane; and, 4) in a newly obtained patch, some of the KCa channels are probably already in a phosphorylated state. 

Received 21 September 1995; accepted in final form 1 March 1996.
APS Manuscript Number L278-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 20 March 96