Diabetes & Metabolism Journal

Original Article

A Differential Effect of Intracellular ATP on Skeletal-and Smooth Muscle-Type KATP Channel Activities.: Oh Dae Kwon, Jeong Geun Lim, Haeng Gyun Kim, Dae Kwang Kim, Jae Seok Hwang, Keun Gyu Park, Sung Hee Park, Chi Heum Cho, In Kyu Lee, Dae Kyu Song; Korean Diabetes J. 2003;27(4):332-342. Published online August 1, 2003

Abstract PDF: BACKGROUND
The ATP-sensitive potassium (KATP) channel comprises an inwardly- rectifying K+ channel (Kir) and a sulfonylurea receptor(SUR). This study investigated the mechanism of different ATP sensitivity between skeletal-(Kir6.2/SUR2A) and smooth muscle- (Kir6.2/SUR2B) type KATP channels. METHODS: Messenger RNAs encoding mouse Kir6.2, and rat SUR2A or 2B were co-injected into Xenopus Laevis oocytes to express each type of KATP channel. Using the inside-out patch clamp technique, the channel currents for MgATP sensitivity were measured and analyzed. RESULTS: By addition of 100 microM of MgATP, the current initially decreased and then slowly increased in Kir6.2/SUR2A. This gradual, ATP sensitivity decrease during prolonged MgATP application was totally blocked by LY 294002, a pho- sphatidylinositol-3 and -4 kinase inhibitor. In contrast, a rather rapid sensitivity decrease after initial inhibition was observed in Kir6.2/SUR2B by 100 microM of ATP, which was not blocked by LY 294002. This channel activation was Mg2+- dependent, suggesting that ATP hydrolysis is critical. CONCLUSION: This result supports the idea that the ability of MgATP to stimulate Kir6.2/SUR2B channels reflects a faster rate of ATP hydrolysis at NBD2 of SUR2B.

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