期刊
JOURNAL OF PHYSIOLOGY-LONDON
卷 559, 期 1, 页码 67-84出版社
WILEY
DOI: 10.1113/jphysiol.2004.066944
关键词
-
资金
- NIDA NIH HHS [DA11322, R01 DA011322] Funding Source: Medline
- NINDS NIH HHS [R37 NS008174, NS08174, T32 NS007332, NS07332, R01 NS008174] Funding Source: Medline
We studied modulation of current in human embryonic kidney tsA-201 cells coexpressing rat erg1 channels with M-1 muscarinic receptors. Maximal current was inhibited 30% during muscarinic receptor stimulation, with a small positive shift of the midpoint of activation. Inhibition was attenuated by coexpression of the regulator of G-protein signalling RGS2 or of a dominant-negative protein, G(q), but not by N-ethylmaleimide or C3 toxin. Overexpression of a constitutively active form of G(q) (but not of G(13) or of G(s)) abolished the erg current. Hence it is likely that G(q/11), and not G(i/o) or G(13), mediates muscarinic inhibition. Muscarinic suppression of erg was attenuated by chelating intracellular Ca2+ to <1 nM free Ca2+ with 20 mM BAPTA in the pipette, but suppression was normal if internal Ca2+ was strongly clamped to a 129 nM free Ca2+ level with a BAPTA buffer and this was combined with numerous other measures to prevent intracellular Ca2+ transients (pentosan polysulphate, preincubation with thapsigargin, and removal of extracellular Ca2+). Hence a minimum amount of Ca2+ was necessary for the inhibition, but a Ca2+ elevation was not. The ATP analogue AMP-PCP did not prevent inhibition. The protein kinase C (PKC) blockers staurosporine and bisindolylmaleimide I did not prevent inhibition, and the PKC-activating phorbol ester PMA did not mimic it. Neither the tyrosine kinase inhibitor genistein nor the tyrosine phosphatase inhibitor dephostatin prevented inhibition by oxotremorine-M. Hence protein kinases are not needed. Experiments with a high concentration of wortmannin were consistent with recovery being partially dependent on PIP2 resynthesis. Wortmannin did not prevent muscarinic inhibition. Our studies of muscarinic inhibition of erg current suggest a role for phospholipase C, but not the classical downstream messengers, such as PKC or a calcium transient.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据