ATP Sensitive Potassium Channel Guo Wei Zhejiang University School of Medicine

1. ATP Sensitive Potassium Channel Guo Wei Zhejiang University School of Medicine

2. Structure • inward-rectifying potassium channel subunit (Kir) :a pore • sulfonylurea receptor (SUR) : a regulatory Kir6.1 Kir6.2 SUR1 SUR2

3. Structure

4. Regulation • the KATP channels are inhibited by direct ATP binding to the Kir pore-forming subunit, preventing K+ flux across the membrane • ATP、Mg2+-ATP、ADP、 Mg2+-ADP

5. Pharmacologic Regulation • Openers :Pinacidil, cromakalim , nicorandil, diazoxide • Blockers :glibenclamide , 5-hydroxy decanoate

6. ATP-sensitive potassium channel subtypes in the myocardium • sarcolemma (sarcKATP) membrane • the inner membrane of the mitochondria(mitoKATP)

7. sarcKATP It’s unnecessary Shortening of the action potential Inhibition of Ca2+ overloading

8. sarcKATP Diazoxide K1/2=840 µmol/L K1/2= 0.8µmol/L mitoKATP

9. It was indeed not the surface but themitoKATPchannelthat was involved in cardioprotection ！

10. ? Cardioprotection mechanism Opening the mitoKATP channel

11. Possible Mechanism • Mitochondrial swelling • Resistant to Ca2+ entry • Release of ROS • Apoptosis

12. mKATP and reactive oxygen species N-acetylcysteine Preconditioning of chick cardiomyocytes with the ACh MPG a small burst of free radicals Blocked Diazoxide’s protection

13. mKATP and reactive oxygen species • 2',7'-dichlorofluorescein diacetate (DCFH) which fluoresces when oxidized by free radicals • This burst could be blocked bymyxothiazol(inhibitor of site III of theelectron transport chain) and5-HD

15. [Ca2+]i  K+ influx the release of free radicals mitochondria membrane depolarization. ? ? ? the release of free radicals the release of free radicals

16. mKATP and downstream kinases • Ashraf’s group showed that the PKC blockerchelerythrinecould blockprotection from a pulse of diazoxide in the isolated rat heart.

17. mKATP and downstream kinases While Pain et al. could not show a similar result in the rabbit heart, they were able to block the diazoxide’s protection with thetyrosine kinase blocker genistein

18. Receptors that couple to the mKATP • It is well known that surface receptors such as adenosine,bradykinin, opioid,a-adrenergic, and muscarinic participate in IPC • Muscarinic receptors coupled to Gi

19. an increase in fluorescence that was not different from by diazoxide phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin muscarinic receptor antagonists including atropine 3-phosphoinositides carry the signal to the interior of the cell ACh Studies using A7r5 vascular smooth muscle cells

20. an increase in fluorescence that was not different from by diazoxide genistein muscarinic receptor antagonists including atropine suggesting that there is also at least one tyrosine kinase in this pathway. ACh

21. Possible Signal transduction pathway • More importantly neither wortmannin nor genistein could block the increased flourescence from diazoxide, again showing PI3-K and tyrosine kinase in this signaling are upstream of mK ATP channels

22. Possible Signal transduction pathway • the PKC blocker chelerythrine did not block the diazoxide-induced increase in fluorescence • Thus data to show PKC must be downstream of KATP and presumably of ROS production

23. G receptor Possible Signal transduction pathway PKC PLC PLD PI3 kinase ROS↑ end effector Tyrosine kinase MitoKATP

24. Thank you !