Compromised ATP binding as a mechanism of phosphoinositide modulation of ATP-sensitive K+ channels.
Inhibition of ATP-sensitive K(+) (K(ATP)) channels by ATP, a process presumably initiated by binding of ATP to the pore-forming subunit, Kir6.2, is reduced in the presence of phosphoinositides (PPIs). Previous studies led to the hypothesis that PPIs compromise ATP binding. Here, this hypothesis was tested using purified Kir6.2. We show that PPIs bind purified Kir6.2 in an isomer-specific manner, that biotinylated ATP analogs photoaffinity label purified Kir6.2, and that this labeling is weakened in the presence of PPIs. Patch-clamp measurements confirmed that these ATP analogs inhibited Kir6.2 channels, and that PPIs decreased the level of inhibition. These results indicate that interaction of PPIs with Kir6.2 impedes ATP-binding activity. The PPI regulation of ATP binding revealed in this study provides a putative molecular mechanism that is potentially pivotal to the nucleotide sensitivity of K(ATP) channels.
Wang
Congmiao
C
Department of Physiology, The University of Tennessee Health Science Center, 894 Union Avenue, Memphis, TN 38163, USA.
Wang
Kun
K
Wang
Wenxia
W
Cui
Yijun
Y
Fan
Zheng
Z
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D004553:Electric Conductivity; D007536:Isomerism; D018408:Patch-Clamp Techniques; D010716:Phosphatidylinositols / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D019920:Photoaffinity Labels / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024661:Potassium Channels, Inwardly Rectifying / Q000302:isolation & purification / Q000378:metabolism* / Q000502:physiology
D010716:Phosphatidylinositols; D019920:Photoaffinity Labels; D026902:Potassium Channel Blockers; D024661:Potassium Channels, Inwardly Rectifying; D000255:Adenosine Triphosphate