T. Nishizaki et K. Sumikawa, NICOTINIC RECEPTORS ARE REGULATED BY PROTEIN-KINASE-C ACTIVATED VIA ANICOTINIC RECEPTORS-MEDIATED SIGNALING PATHWAY, Molecular brain research, 61(1-2), 1998, pp. 211-218
The present study was conducted to examine the effect of protein kinas
e C (PKC) on nicotinic acetylcholine (ACh) receptors expressed in Xeno
pus oocytes by monitoring single-channel currents. In an outside-out p
atch-clamp configuration, ACh (1 mu M) elicited single channel current
s with a slope conductance of 31 pS (control) in normal Torpedo ACh re
ceptors. Activation of PKC via an endogenous phosphatidylinositol sign
aling pathway elevated the slope conductance to 41 pS, which effect wa
s blocked by the selective PKC inhibitor, staurosporine. Mutant ACh re
ceptor channels, which mimic PKC phosphorylation of the receptors, exh
ibited a slope conductance of 41 pS. Notably, pretreatment with a high
er concentration of ACh (100 mu M) caused an increase in the slope con
ductance of the channels for 1 mu M ACh (43 pS), which was the same le
vel as obtained with either PKC activation or mutant ACh receptors, an
d this effect was also inhibited by staurosporine. In addition, the co
ntrol slope conductance was reduced by PKC inhibitor peptide (24 pS),
which corresponded to that obtained with another mutant ACh receptors
lacking PKC phosphorylation sites (18 pS). Mouse muscle ACh receptors
were also regulated by the same mechanism. The results of the present
study suggest that ACh activates PKC via nicotinic ACh receptors, whic
h alternatively, modulates the properties of the receptor channels. (C
) 1998 Elsevier Science B.V. All rights reserved.