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SERCA2 regulates proinsulin processing and processing enzyme maturation in the pancreatic β cell

Iida, H.; Kono, T. M.; Lee, C.-C.; Krishnan, P.; Arvin, M. C.; Weaver, S. A.; Jarvela, T. S.; Bone, R. N.; Tong, X.; Arvan, P.; Lindberg, I.; Evans-Molina, C.

2022-06-17 physiology
10.1101/2022.06.13.495980 bioRxiv
Show abstract

Increased circulating levels of incompletely processed insulin (i.e. proinsulin) are observed clinically in both type 1 and type 2 diabetes; however, the mechanisms underlying impaired proinsulin processing remain incompletely understood. Here, we identify the sarcoendoplasmic reticulum Ca2+ ATPase-2 (SERCA2) pump and {beta} cell ER Ca2+ as key regulators of systemic glucose tolerance and proinsulin processing. We generated mice with a {beta} cell-specific SERCA2 deletion ({beta}S2KO) and SERCA2 deficient INS-1 cells to show that SERCA2 loss increases systemic and pancreatic levels of proinsulin protein and leads to aberrant localization of proinsulin within the proximal {beta} cell secretory pathway. These defects in proinsulin processing were linked to reduced maturation of the proinsulin processing enzymes PC1/3 and PC2, suggesting a model whereby chronic ER Ca2+ depletion in the {beta} cell, which is observed in many pathological conditions, impairs the spatial regulation of prohormone trafficking, processing, and maturation within the {beta} cell secretory pathway.

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