Phosphatidylinositol 4,5-bisphosphate is acting as a signal molecule in alpha(1)-adrenergic pathway via the modulation of acetylcholine-activated K+ channels in mouse atrial myocytes
H. Cho et al., Phosphatidylinositol 4,5-bisphosphate is acting as a signal molecule in alpha(1)-adrenergic pathway via the modulation of acetylcholine-activated K+ channels in mouse atrial myocytes, J BIOL CHEM, 276(1), 2001, pp. 159-164
We have investigated the effect of alpha (1)-adrenergic agonist phenylephri
ne (PE) on acetylcholine-activated K+ currents (I-KACh). I-KACh was recorde
d in mouse atrial myocytes using the patch clamp technique. I-KACh was acti
vated by 10 muM ACh and the current decreased by 44.27 +/- 2.38% (n = 12) d
uring 4 min due to ACh-induced desensitization. When PE was applied with AC
h, the extent of desensitization was markedly increased to 69.34 +/- 2.22%
(n = 9), indicating the presence of PE-induced desensitization, I-KACh was
fully recovered from desensitization after a 6-min washout. PE-induced dese
nsitization of I-KACh was not affected by protein kinase C inhibitor, calph
ostin C, but abolished by phospholipase C (PLC) inhibitor, neomycin, When p
hophatidylinositol 4,5-bisphosphate (PIP2) replenishment was blocked by wor
tmannin (an inhibitor of phophatidylinositol 3-kinase and phophatidylinosit
ol 4-kinase), desensitization of I,,, in the presence of PE was further inc
reased (97.25 +/- 7.63%, n = 6), Furthermore, the recovery from PE-induced
desensitization was inhibited, and the amplitude of I,, at the second expos
ure after washout was reduced to 19.65 +/- 2.61% (n = 6) of the preceding l
evel. These data suggest that the K-ACh, channel is modulated by PE through
PLC stimulation and depletion of PIP2.