Diabetologie und Stoffwechsel 2019; 14(S 01): S3
DOI: 10.1055/s-0039-1688110
ePoster
Beta-Zelle I
Georg Thieme Verlag KG Stuttgart · New York

ATP triggers Katp channel opening without hydrolysis

J Sikimic
1   Universität Tübingen, Pharmazeutisches Institut für Pharmakologie, Toxikologie und Klinische Pharmazie, Tübingen, Germany
,
J Bryan
2   Pacific Northwest Research Institute, Pacific Northwest Research Institute, Seattle, United States
,
P Krippeit-Drews
3   University of Tübingen, Institute of Pharmacy, Department of Pharmacology, Toxicology and Clinical Chemistry, Tübingen, Germany
,
G Drews
3   University of Tübingen, Institute of Pharmacy, Department of Pharmacology, Toxicology and Clinical Chemistry, Tübingen, Germany
› Author Affiliations
Further Information

Publication History

Publication Date:
07 May 2019 (online)

Also available at
 

Objective:

KATP channels, (SUR1/Kir6.2)4, couple the membrane potential of neuroendocrine cells to their metabolic state. Channel activity is regulated positively by ATP and ADP binding to SUR1 and negatively by nucleotide binding to Kir6.2. It is hypothesized that channel opening requires MgATP hydrolysis by SUR1.

The aim of the study was to test whether solely ATP binding, without hydrolisis, is sufficient for channel activation.

Methods:

Stable transfected HEK-293 cells coexpressing wildtype or mutant hamster Abcc8/SUR1 and wildtype or mutant human Kcnj11/Kir6.2 were used. Channel activity was tested between 24 – 72 hours after activation with doxicyclin (300µM) using the inside/out configuration of the patch clamp technnique.

Results:

To test the hypothesis we used recombinant KATP channels whose Kir6.2G334D pore subunits are poorly inhibited by ATP and whose regulatory SUR1Q1178R or SUR1E1507Q subunits have increased affinities for ATP. Additionally, the E1507Q substitution replaces the catalytic glutamate needed for efficient hydrolysis. Both channels were significantly activated by 10mM ATP4-(open probability (NPo) increased from 0.22 ± 0.14 to 0.99 ± 0.53 (n = 6) and from 0.08 ± 0.03 to 0.99 ± 0.53 (n = 6), respectively). 10mM GTP4 significantly elevated NPo for SUR1 Q1178R/Kir6.2G334D (from 0.33 ± 0.12 to 0.86 ± 0.25 (n = 6)). In addition, diazoxide which is thought to act only with ATP hydrolysis, opened channels expressing wildtype Kir6.2 and SUR1E1507K in the presence of ATP4-.

Conclusion:

Our findings show that ATP acts as a KATP channel agonist probably by switching SUR1 from inward to outward facing conformation which triggers channel openings.