ATP regulates cardiac Ca2+ channel activity via a mechanism independent of protein phosphorylation.
The role of adenosine triphosphate (ATP) in the regulation of L-type Ca2+ channel activity was investigated in inside-out patches from guinea-pig ventricular cells, in which the Ca2+ channel activity had been reprimed by application of cytoplasm from bovine heart. Passing the cytoplasm through a diethylaminoethyl (DEAE)-sepharose column or heating at 60 degrees C for 20 min attenuated the induction Ca2+ channel activity to 6-13% of that in the preceding cell-attached patch. Addition of 10 mM MgATP to the cytoplasm greatly improved the potency of cytoplasm in restoring Ca2+ channel activity (to 83 +/- 22%, mean +/- SE). This effect of MgATP was also produced, although with lower potency, by K2ATP (61 +/- 20%) or 5'-adenylylimidodiphosphate (AMP-PNP, 39 +/- 7%), a non-hydrolyzable ATP analogue, suggesting that hydrolysis of ATP is not required for the stimulatory effect on channel activity. A non-specific protein kinase inhibitor H8 (50-100 microM) did not inhibit the effect of cytoplasm + MgATP on channel activity, suggesting the involvement of a pathway independent of phosphorylation. We conclude that ATP regulates Ca2+ channel activity in dual pathways: one with, and the other without, protein phosphorylation.
Yazawa
K
K
Department of Pharmacology, Asahikawa Medical College, Asahikawa 078, Japan.
Kameyama
A
A
Yasui
K
K
Li
J M
JM
Kameyama
M
M
D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D002417:Cattle; D003593:Cytoplasm / Q000378:metabolism; D004983:Ethanolamines / Q000494:pharmacology; D006168:Guinea Pigs; D006358:Hot Temperature; D009206:Myocardium / Q000378:metabolism; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism*
D015220:Calcium Channels; D004983:Ethanolamines; D011506:Proteins; D000255:Adenosine Triphosphate; C007369:2-diethylaminoethanol