Introduction & Objective: MOTS-c is a mitochondrial DNA-encoded microprotein that improves impaired glucose metabolism caused by aging and high fat diet. The presence of a naturally occurring genetic variant of MOTS-c, K14Q MOTS-c, increases the susceptibility to type 2 diabetes (T2D) in East Asians. Nevertheless, the precise mechanism of MOTS-c action has not been fully elucidated. Here, we demonstrate that the protein kinase CK2 is a functional and direct target of MOTS-c and that the reduced binding of K14Q MOTS-c to CK2 increases the risk of T2D.
Methods: We performed in vitro experiments, including dot blot, kinase activity, and surface plasmon resonance assays, to investigate the direct interaction between MOTS-c and CK2. We also examined the impact of MOTS-c treatment on CK2 activity in skeletal muscle, as well as on muscle glucose uptake in young mice. Subsequently, we investigated the impact of a naturally occurring K14Q MOTS-c variant on the prevalence of T2D in 12,068 Japanese individuals.
Results: Dot blot and cell-free kinase activity assays demonstrated that MOTS-c activated CK2 by binding directly to its α subunit, and this binding was confirmed using a surface plasmon resonance assay. Importantly, the binding affinity of K14Q MOTS-c to CK2α was 16-fold less than that of the wild type MOTS-c, and K14Q MOTS-c did not activate CK2 in the cell-free kinase activity assay. Skeletal muscle CK2 activity was lower in old mice and higher after exercise, and was increased by MOTS-c administration, but not K14Q MOTS-c. MOTS-c administration, but not K14Q MOTS-c, significantly enhanced muscle glucose uptake, which was blunted by a CK2 inhibitor. In humans, the K14Q MOTS-c carriers exhibited an increased risk of type 2 diabetes, particularly among individuals aged 60 and above, while this increased risk was mitigated by daily physical activity.
Conclusion: Together, these findings provide evidence that CK2 is required for MOTS-c effects and that the MOTS-c/CK2 pathway is a potential therapeutic target for T2D.<u></u>
H. Kumagai: None. S. Kim: None. B. Miller: None. S. Lee: None. H. Zempo: None. T. Natsume: None. J. Wan: None. R. Ramirez II: None. H.H. Mehta: None. Y. Nishida: None. N. Fuku: None. S. Dobashi: None. E. Miyamoto-Mikami: None. H. Naito: None. M. Hara: None. C. Iwasaka: None. Y. Yamada: None. Y. Higaki: None. K. Tanaka: None. K. Yen: None. P. Cohen: None.
