Vitamin K-dependent carboxylation regulates Ca²⁺ flux and adaptation to metabolic stress in β cells.

ABSTRACT: Vitamin K is a micronutrient necessary for γ-carboxylation of glutamic acids. This post-translational modification occurs in the endoplasmic reticulum (ER) and affects secreted proteins. Recent clinical studies implicate vitamin K in the pathophysiology of diabetes, but the underlying molecular mechanism remains unknown. Here, we show that mouse β cells lacking γ-carboxylation fail to adapt their insulin secretion in the context of age-related insulin resistance or diet-induced β cell stress. In human islets, γ-carboxylase expression positively correlates with improved insulin secretion in response to glucose. We identify endoplasmic reticulum Gla protein (ERGP) as a γ-carboxylated ER-resident Ca²⁺-binding protein expressed in β cells. Mechanistically, γ-carboxylation of ERGP protects cells against Ca²⁺ overfilling by diminishing STIM1 and Orai1 interaction and restraining store-operated Ca²⁺ entry. These results reveal a critical role of vitamin K-dependent carboxylation in regulation of Ca²⁺ flux in β cells and in their capacity to adapt to metabolic stress.

SUBMITTER: Lacombe J 

PROVIDER: S-EPMC10305719 | biostudies-literature | 2023 May

REPOSITORIES: biostudies-literature