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Vitamin K-dependent carboxylation regulates calcium flux and adaptation to metabolic stress in β-cells

Lacombe, J.; Guo, K.; Bonneau, J.; Faubert, D.; Gioanni, F.; Vivoli, A.; Muir, S. M.; Hezzaz, S.; Poitout, V.; Ferron, M.

2023-02-24 cell biology
10.1101/2022.05.13.491370 bioRxiv
Show abstract

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

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