OR34-06 Protein kinase A signaling fully rescues defective cyclic AMP production in pancreatic beta-cells in mice

Abstract Disclosure: A.J. Castro: None. J. Childress: None. M. Rios: None. M. Shehada: None. M.A. Hussain: None. The cyclic AMP (cAMP) intracellular signaling pathway is essential for regulating cellular and metabolic processes. In pancreatic beta-cells the incretin hormones Glucagon-like peptide-1, Glucose-dependent insulinotropic peptide (GIP) upon binding their cognate G-protein coupled receptors (GPCR) activate G-protein Gsα (Gnas) to potently stimulate cAMP synthesis. Cyclic AMP in turn activates protein kinase A signaling by primarily interacting with the regulatory PKA subunit 1a (Prkar1a), thereby releasing and disinhibiting PKA catalytic subunit (PKAc). Whether cAMP signaling in beta cells is solely mediated by PKA remains unknown. To address this question, we used the CRE-LoxP system to conditionally ablate Gsα in β-cells of mice to achieve diminished cAMP levels selectively in β-cells (β-ΔGsα). As expected, these mice exhibited elevated fasting glycemia and severely disturbed glycemic control during intraperitoneal glucose tolerance tests (ipGTT). To examine to what extent disinhibition of PKAc might functionally rescue the absence of cAMP production in β-cells we also ablated one or both alleles of the PKA regulatory subunit 1a (Prkar1a) in β-cells of β -ΔGsα mice to yield β-ΔGsα-ΔPrkar1ahet and β-ΔGsα-ΔPrkar1ahom mice. β-ΔGsα mice have severely defective glucose stimulated insulin secretion (GSIS). Surprisingly, in β-ΔGsα mice additional ablation of only one Prkar1a allele (β-ΔGsα-ΔPrkar1ahet) was sufficient to normalize glycemic control. Moreover, β-ΔGsα-ΔPrkar1ahom mice showed improved glycemic control owing to significantly augmented GSIS, thereby maintaining blood glucose near basal levels throughout ipGTT. In perifusion studies of islets isolated from β-ΔGsα, β-ΔGsα-ΔPrkar1ahet, β-ΔGsα-ΔPrkar1ahom, ablation of one Prkar1a allele restores cell function in even in absence of Gsα. Furthermore, inhibition of the IP3 receptor (Xestospongin, X) of perifused WT islets reverses GLP-1 effects on augmenting GSIS; and X treatment of β-ΔGsα-ΔPrkar1ahet reverses the effects of single allele Prkar1a ablation. In contrast, IP3R inhibition in β-ΔGsα-ΔPrkar1ahom islets had not influence on augmented GSIS. These findings highlight the importance of PKA signaling in regulating β-cell function where PKA mediates most if not all cAMP-dependent signaling. Our findings also highlight the interplay of PKA signaling and IP3R in regulating glucose-stimulated insulin release. Complete ablation of Prkar1a and disinhibition of PKA signaling has effects on GSIS that override IP3R inhibition, the mechanisms for which remain to be examined. Given that β-cell cAMP production is hampered in diabetes, we propose Prkar1a as an ideal therapeutic target to rescue β-cell function. Presentation: Monday, July 14, 2025