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The gating of nucleotide-sensitive K+ channels in insulin-secreting cells can be modulated by changes in the ratio ATP4-/ADP3- and by nonhydrolyzable derivatives of both ATP and ADP.

Authors :
Dunne MJ
West-Jordan JA
Abraham RJ
Edwards RH
Petersen OH
Source :
The Journal of membrane biology [J Membr Biol] 1988 Sep; Vol. 104 (2), pp. 165-77.
Publication Year :
1988

Abstract

The 31P-NMR technique has been used to assess the intracellular ratios and concentrations of mobile ATP and ADP and the intracellular pH in an insulin-secreting cell line, RINm5F. The single-channel current-recording technique has been used to investigate the effects of changes in the concentrations of ATP and ADP on the gating of nucleotide-dependent K+ channels. Adding ATP to the membrane inside closes these channels. However, in the continued presence of ATP adding ADP invariably leads to the reactivation of ATP-inhibited K+ channels, even at ATP4-/ADP3- concentration ratios greater than 7:1. Interactions between ATP4- and ADP3- seem competitive. An increase in the concentration ratio ATP4-/ADP3- consistently evoked a decrease in the open-state probability of K+ channels; conversely, a decrease in ATP4-/ADP3- increased the frequency of K+ channel opening events. Channel gating was also influenced by changes in the absolute concentrations of ATP4- and ADP3-, at constant free concentration ratios. ADP-evoked stimulation of ATP-inhibited channels did not result from phosphorylation of the channel, as ADP-beta-S, a nonhydrolyzable analog of ADP, not only stimulated but enhanced ADP-induced activation of K+ channels, in the presence of ATP. Similarly, ADP was able to activate K+ channels in the presence of two nonhydrolyzable derivatives of ATP, AMP-PNP and beta gamma methylene ATP.

Details

Language :
English
ISSN :
0022-2631
Volume :
104
Issue :
2
Database :
MEDLINE
Journal :
The Journal of membrane biology
Publication Type :
Academic Journal
Accession number :
3057214
Full Text :
https://doi.org/10.1007/BF01870928