An adenylate kinase is involved in KATP channel regulation of mouse pancreatic beta cells.
OBJECTIVE
In a previous study, we demonstrated that a creatine kinase (CK) modulates K(ATP) channel activity in pancreatic beta cells. To explore phosphotransfer signalling pathways in more detail, we examined whether K(ATP) channel regulation in beta cells is determined by a metabolic interaction between adenylate kinase (AK) and CK.


METHODS
Single channel activity was measured with the patch-clamp technique in the inside-out (i/o) and open-cell attached (oca) configuration.


RESULTS
The ATP sensitivity of K(ATP) channels was higher in i/o patches than in permeabilised beta cells (oca). One reason for this observation could be that the local ATP:ADP ratio in the proximity of the channels is determined by factors not active in i/o patches. AMP (0.1 mmol/l) clearly increased open channel probability in the presence of ATP (0.125 mmol/l) in permeabilised cells but not in excised patches. This suggests that AK-catalysed ADP production in the vicinity of the channels is involved in K(ATP) channel regulation. The observation that the stimulatory effect of AMP on K(ATP) channels was prevented by the AK inhibitor P (1),P (5)-di(adenosine-5')pentaphosphate (Ap(5)A; 20 micromol/l) and abolished in the presence of the non-metabolisable ATP analogue adenosine 5'-(beta,gamma-imido)triphosphate tetralithium salt (AMP-PNP; 0.12 mmol/l) strengthens this idea. In beta cells from AK1 knockout mice, the effect of AMP was less pronounced, though not completely suppressed. The increase in K(ATP) channel activity induced by AMP in the presence of ATP was outweighed by phosphocreatine (1 mmol/l). We suggest that this is due to an elevation of the ATP concentration by CK.


CONCLUSIONS
We propose that phosphotransfer events mediated by AK and CK play an important role in determining the effective concentrations of ATP and ADP in the microenvironment of pancreatic beta cell K(ATP) channels. Thus, these enzymes determine the open probability of K(ATP) channels and eventually the actual rate of insulin secretion.
Schulze
D U
DU
Institute of Pharmacy, Department of Pharmacology, University of Tübingen, Auf der Morgenstelle 8, 72076, Tübingen, Germany.
Düfer
M
M
Wieringa
B
B
Krippeit-Drews
P
P
Drews
G
G
D000249:Adenosine Monophosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000502:physiology; D000263:Adenylate Kinase / Q000378:metabolism*; D000818:Animals; D004594:Electrophysiology / Q000379:methods; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000502:physiology*; D054086:KATP Channels / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D018408:Patch-Clamp Techniques
D054086:KATP Channels; D000249:Adenosine Monophosphate; D000255:Adenosine Triphosphate; D000263:Adenylate Kinase
FEBS Lett. 1986 Nov 10;208(1):63-6
2429869
Mol Cell Biochem. 2004 Jan-Feb;256-257(1-2):243-56
14977185
Diabetologia. 1979 May;16(5):331-41
37138
Proc Natl Acad Sci U S A. 1996 May 14;93(10):5161-5
8643546
Biochem Pharmacol. 1997 Jul 15;54(2):219-25
9271325
J Biol Chem. 1973 Feb 10;248(3):1121-3
4734335
J Physiol. 2002 Dec 1;545(Pt 2):501-7
12456829
Diabetes. 2004 Dec;53 Suppl 3:S63-6
15561924
FASEB J. 2002 Jan;16(1):102-4
11729098
Science. 1996 Jun 21;272(5269):1785-7
8650576
Biochim Biophys Acta. 1987 Feb 18;927(2):190-5
2434137
Mol Cell Endocrinol. 2005 Jan 31;230(1-2):51-8
15664451
EMBO J. 2000 Dec 1;19(23 ):6371-81
11101510
J Biol Chem. 1998 Nov 20;273(47):31395-400
9813050
Diabetes. 1980 Jan;29(1):1-14
6991311
J Biol Chem. 1991 Dec 5;266(34):22887-92
1744082
Nature. 1984 Sep 20-26;311(5983):271-3
6090930
J Biol Chem. 1996 Dec 13;271(50):31903-8
8943234
FEBS Lett. 1989 Nov 6;257(2):361-4
2555221
Biochem J. 2003 Oct 1;375(Pt 1):1-16
12839490
J Physiol. 1990 Apr;423:91-110
2388163
Diabetes. 2003 Oct;52(10):2630-5
14514649
Diabetes. 2006 Oct;55(10):2826-34
17003349
Diabetes. 1996 Oct;45(10):1431-4
8826982
Proc Natl Acad Sci U S A. 2001 Jun 19;98(13):7623-8
11390963
J Physiol. 1993 Apr;463:349-65
8246187
J Biol Chem. 1996 Jul 12;271(28):16544-52
8663240
Nucleic Acids Res. 2005 Jan 1;33(Database issue):D544-9
15608258
J Biol Chem. 1998 Dec 18;273(51):33905-8
9852040
Pflugers Arch. 2003 Feb;445(5):556-62
12634926
Diabetes. 1972;21(2 Suppl):555-69
4559920
J Membr Biol. 1988 Sep;104(2):165-77
3057214
J Biol Chem. 1998 Oct 9;273(41):26383-7
9756869
Science. 1998 Nov 6;282(5391):1141-4
9804555
J Physiol. 1985 Jun;363:441-62
2410608
J Biol Chem. 2006 Feb 3;281(5):3006-12
16332676
Diabetes. 2006 Sep;55(9):2446-54
16936192
Endocr Rev. 1999 Apr;20(2):101-35
10204114
J Physiol. 1988 Oct;404:731-47
2855352
Diabetes. 2005 Oct;54(10 ):2852-2858
16186385
FASEB J. 1998 May;12(7):523-9
9576479
Science. 1998 Nov 6;282(5391):1059-60
9841452
J Endocrinol. 1986 May;109(2):201-7
2423630
Science. 1998 Nov 6;282(5391):1138-41
9804554
Diabetes. 2002 Feb;51(2):376-84
11812744
Nature. 1997 May 8;387(6629):179-83
9144288
J Exp Biol. 2003 Jun;206(Pt 12):2039-47
12756286