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Positive allosteric modulators of VPAC1 receptor-mediated ERK activation
Abbott, Justin
Abbott, Justin
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Abstract
Vasoactive intestinal peptide (VIP) is a neuroendocrine peptide that has been implicated in a myriad of functions. VIP promotes neuronal survival during development and apoptotic challenges. Further, VIP has been shown to regulate hormonal release, circadian rhythms, vasodilation, and T cell proliferation in central and peripheral tissues. VIP binds with equally high affinity to VPAC1 and VPAC2 receptors, members of the Class B family of G protein-coupled receptors (GPCRs) that also include the PAC1, glucagon (GCGR), and CRH receptors. VIP binding has previously been shown to increase downstream MAPK signaling cascades, especially MEK/ERK. Given the structural similarities and functional overlap between VPAC1 and VPAC2 receptors, we sought to investigate whether there are small molecule modulators that can probe and identify the functional distinctions between the two receptor subtypes. For these studies, we used HEK-293 cells stably expressing the VPAC1-EGFP or the VPAC2-EGFP receptor. The cultures were treated with VIP with and without the addition of putative small molecule antagonists. Protein assays and western blotting analysis for phosphorylated ERK (pERK) were performed to define quantitative changes in ERK activation. Many compounds in the small molecule panel were non-selective antagonists at the VPAC1 and VPAC2 receptors. Interestingly, an acyl hydrazide compound, I48, and a previously described glucagon receptor antagonist, MK-0893, behaved as positive allosteric modulators at the VPAC1 receptor on ERK activation, but not at the VPAC2 receptor. Our results suggest that these compounds can uniquely restrict the conformational microstate of the VPAC1 receptor to amplify VIP-mediated ERK signaling.
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2018-01-01
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Neurological Sciences