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KMID : 0358619960300020209
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Korean Journal of Physiology
1996 Volume.30 No. 2 p.209 ~ p.218
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Modulatory Effect of the Tyrosine Kinase and Tyrosine Phosphatase on the ACh-activated Channel in Adult Rat Atrial Cells
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Chang Kyeong-Jae
Rhie Sang-Ho
Heo Ilo
Kim Yang-Mi
Haan Jae-Hee
Hong Seong-Geun
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Abstract
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Acetylcholine (ACh) activates the inwardly rectifying muscarinic channel in rat atrial cells via pertussis toxin (PTX)-sensitive G-protein () coupled with the muscarinic receptor (mAChR). Although this channel function has reported to be modulated by the phosphorylation process, a kinase and phosphatase involved in these processes are still unclear. Since either PKA or PKC was not effective on this ATP-modulation, the present study examined the possible involvement of the protein tyrosine kinase (PTK) and protein tyrosine phosphatase (PTP) in the function of the Channel. In the inside-out (I/O) patch preparation excised from the adult rat atrial cell, when activated by 10 ACh in the pipette and 100 GTP in the bath, the mean open time () and the channel activity () was 1.13 ms (n=5) and 0.19 (n=6), respectively. Following the application of 1 mM ATP into the bath, increased by 34% (1.54 ms, n=5) and by 66% (0.28, n=6). Channel function elevated by ATP was lasted after washout of ATP. However, this ATP-induced increase in the channel function did not occur in pretreated cells with genistein (), a selective PTK inhibitor, but occurred in pretreated cells with equimolar daidzein, a negative control of the genistein. On the contrary, PTP which acts on tyrosine residue conversely reversed both ATP-induced increased by 32% (1.20 ms, n=3) and by 41% (0.15, n=3), respectively. Taken together, these results suggest that channel may, at least partly, be regulated by the tyrosyl phosphorylation, although it is unclear where this process exerts on the muscarinic signal transduction pathway comprising the mAChR--the channel.
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KEYWORD
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ACh-activated $K^{+}\, (K_{ACh})$ channel, phosphorylation, tyrosine kinase, tyrosyl phosphatase, single channel study, Rat atrial cell
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