Deletion of CDKAL1 affects mitochondrial ATP generation and first-phase insulin exocytosis

• Published in: PloS one Vol. 5; no. 12; p. e15553
• Main Authors: Ohara-Imaizumi, Mica, Yoshida, Masashi, Aoyagi, Kyota, Saito, Taro, Okamura, Tadashi, Takenaka, Hitoshi, Akimoto, Yoshihiro, Nakamichi, Yoko, Takanashi-Yanobu, Rieko, Nishiwaki, Chiyono, Kawakami, Hayato, Kato, Norihiro, Hisanaga, Shin-ichi, Kakei, Masafumi, Nagamatsu, Shinya
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 09.12.2010; Public Library of Science (PLoS)
• Subjects: Adenosine Triphosphate - metabolism; Animals; ATP; B-Lymphocytes - metabolism; Behavior; Biochemistry; Biology; Brain research; Calcium channels; Channels; Clonal deletion; Cyclin-dependent kinase 5; Cyclin-Dependent Kinase 5 - genetics; Cyclin-Dependent Kinase 5 - metabolism; Cytosol - metabolism; Diabetes; Diabetes mellitus; Diabetes Mellitus, Type 2 - metabolism; Endocrinology; Exocytosis; Fluorescence; Genetic aspects; Genetic Variation; Genomes; Glucose; Glucose - metabolism; Homology; Infectious diseases; Insulin; Insulin - metabolism; Kinases; Medicine; Mice; Mice, Knockout; Microscopy; Mitochondria; Mitochondria - metabolism; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - physiology; Pancreas; Patch-Clamp Techniques; Phosphorylation; Potassium; Potassium - chemistry; Proteins; Regulation; Rodents; Type 2 diabetes
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0015553

A variant of the CDKAL1 gene was reported to be associated with type 2 diabetes and reduced insulin release in humans; however, the role of CDKAL1 in β cells is largely unknown. Therefore, to determine the role of CDKAL1 in insulin release from β cells, we studied insulin release profiles in CDKAL1 gene knockout (CDKAL1 KO) mice. Total internal reflection fluorescence imaging of CDKAL1 KO β cells showed that the number of fusion events during first-phase insulin release was reduced. However, there was no significant difference in the number of fusion events during second-phase release or high K(+)-induced release between WT and KO cells. CDKAL1 deletion resulted in a delayed and slow increase in cytosolic free Ca(2+) concentration during high glucose stimulation. Patch-clamp experiments revealed that the responsiveness of ATP-sensitive K(+) (K(ATP)) channels to glucose was blunted in KO cells. In addition, glucose-induced ATP generation was impaired. Although CDKAL1 is homologous to cyclin-dependent kinase 5 (CDK5) regulatory subunit-associated protein 1, there was no difference in the kinase activity of CDK5 between WT and CDKAL1 KO islets. We provide the first report describing the function of CDKAL1 in β cells. Our results indicate that CDKAL1 controls first-phase insulin exocytosis in β cells by facilitating ATP generation, K(ATP) channel responsiveness and the subsequent activity of Ca(2+) channels through pathways other than CDK5-mediated regulation.