232-OR: STIM1 Interacts with G Protein–Coupled Estrogen Receptor Signaling to Maintain ß-Cell Identity in Female Mice

Abstract

Calcium (Ca2+) plays a vital role in normal β cell function, and the β cell endoplasmic reticulum (ER) serves as the dominant intracellular store of Ca2+. ER Ca2+ depletion triggers a rescue mechanism known as store-operated Ca2+ entry (SOCE), which replenishes ER Ca2+ stores through the ER-localized Ca2+ sensor stromal interaction molecule 1 (STIM1). We have demonstrated pathogenic reductions in β cell SOCE and loss of STIM1 expression in rodent and human models of type 2 diabetes (T2D) and shown that β cell-specific loss of STIM1 (STIM1Δβ) leads to obesity-induced glucose intolerance, decreased β cell and increased cell mass in female but not male STIM1Δβ mice. To test mechanisms underlying these findings, lineage tracing experiments were performed and revealed increased colocalization of tdTomato and glucagon in STIM1Δβ mice compared to control mice, suggesting dedifferentiation of β cells to ⍺ cells. RNA sequencing of islets isolated from female STIM1Δβ mice revealed reductions in G-protein coupled estrogen receptor (GPER) expression and a transcriptional signature indicative of reduced estradiol mediated signaling. To test whether GPER is required for the maintenance of β cell identity, INS-1 cells were transfected with siRNA targeted to Gper1 or treated with the GPER1 antagonist, G-15. RT-qPCR showed that markers of β cell identity were significantly reduced and Gcg expression was significantly increased in Gper1 knockdown and G-15-treated cells. Lastly, to explore the functional connection between SOCE and GPER, STIM1KO and GPER knockdown INS-1 cells were stimulated with glucose, and Ca2+ responses were evaluated. First and second phase Ca2+ responses after glucose treatment were impaired in both STIM1KO and GPER knockdown INS-1 cells compared to WT INS-1 cells, suggesting that STIM1 and GPER may be functionally linked through Ca2+ signaling. Together, these data identify a novel connection between β cell SOCE, GPER signaling, and β cell differentiation status. Disclosure M.Mclaughlin: None. P.Sohn: None. P.Krishnan: None. C.Lee: None. T.Kono: None. C.Evans-molina: Advisory Panel; Provention Bio, Inc., DiogenX, Avotres Inc., Neurodon, MaiCell Therapeutics, Other Relationship; Isla Technology, Bristol-Myers Squibb Company, Nimbus Therapeutics, Research Support; Lilly, Astellas Pharma Inc. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK093954, R01DK127236, U01DK127786, R01DK127308, UC4DK104166); U.S. Department of Veterans Affairs (I01BX001733)