Suppression of Adenylate Kinase Catalyzed Phosphotransfer Precedes and Is Associated with Glucose-induced Insulin Secretion in Intact HIT-T15 Cells

• Published in: The Journal of biological chemistry Vol. 271; no. 28; pp. 16544 - 16552
• Main Authors: Olson, L. Karl, Schroeder, William, Robertson, R. Paul, Goldberg, Nelson D., Walseth, Timothy F.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 12-07-1996; American Society for Biochemistry and Molecular Biology
• Subjects: Adenosine Diphosphate - metabolism; Adenosine Triphosphate - metabolism; Adenylate Kinase - antagonists & inhibitors; Adenylate Kinase - metabolism; Animals; Calcium - metabolism; Catalysis; Cell Line; Cricetinae; Extracellular Space - metabolism; Glucose - pharmacology; Insulin - metabolism; Insulin Secretion; Islets of Langerhans - drug effects; Islets of Langerhans - metabolism; Lactates - biosynthesis; Lactic Acid; Membrane Potentials; Mesocricetus; Phosphorus Radioisotopes; Phosphorylation; Potassium Channels - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.271.28.16544

Adenine nucleotide metabolism was characterized in intact insulin secreting HIT-T15 cells during the transition from non-stimulated (i.e. 0.2 mM glucose) to the glucose-stimulated secretory state. Metabolic dynamics were monitored by assessing rates of appearance of 18O-labeled phosphoryls of endogenous nucleotides in cells incubated in medium enriched in [18O]water. Most prominent of the metabolic alterations associated with stimulated insulin secretion was the suppression in the rate of adenylate kinase (AK)-catalyzed phosphorylation of AMP by ATP. This was manifest as a graded decrease of up to 50% in the rate of appearance of β-18O-labeled species of ADP and ATP and corresponded to the magnitude of the secretory response elicited over a range of stimulatory glucose concentrations. The only nucleotide exhibiting a significant concentration change associated with suppression of AK activity was AMP, which decreased by about 50%, irrespective of the glucose concentration. Leucine-stimulated secretion also decreased the rate of AK-catalyzed phosphotransfer. This secretory stimulus-related suppression of AK-catalyzed phosphotransfer occurs within 45 s of glucose addition, precedes insulin secretion, depends on the internalization and metabolism of glucose, and is independent of membrane depolarization and the influx of extracellular calcium. The secretory stimulus-induced decrease in AK-catalyzed phosphotransfer, therefore occurs prior to or at the time of K+ATP channel closure but it is not associated with or a consequence of events occurring subsequent to K+ATP channel closure. These results indicate that AK-catalyzed phosphotransfer may be a determinant of ATP to ADP conversion rates in the K+ATP channel microenvironment; secretory stimuli-linked decreased rates of AK-catalyzed ADP generation from ATP (and AMP) would translate into an increased probability of ATP-liganded and, therefore, closed state of the channel.