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The 5TM VPAC1 Isoform Blocks cAMP Signaling Evoked from the Full‐Length 7TM receptor
Author(s) -
Wilkerson Erich Raymond,
Hermann Rebecca J,
Branch Donald R,
Dorsam Glenn
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.815.2
Subject(s) - vasoactive intestinal peptide , heterotrimeric g protein , gene isoform , gs alpha subunit , receptor , g protein coupled receptor , intracellular , gene knockdown , adenylate kinase , microbiology and biotechnology , pertussis toxin , adenylyl cyclase , camp dependent pathway , gi alpha subunit , biology , signal transduction , g protein , chemistry , medicine , neuropeptide , biochemistry , gene
Vasoactive intestinal peptide receptor 1 (VPAC1) couples heterotrimeric G proteins, Gαs and Gαi, that activate and inhibit adenylate cyclase cAMP production. The 7 transmembrane (TM) VPAC1 isoform, increases intracellular cAMP ([cAMP]i) upon binding its ligand, vasoactive intestinal peptide (VIP). In contrast, the 5TM VPAC1 isoform fails to increase [cAMP]i over a range of 10‐6‐10‐12 M VIP. Our hypothesis is that the dual expression of both the 5 and 7TM isoforms cause a lack of [cAMP]i elevation due to an antagonist effect by the 5TM on 7TM signaling. To investigate this, human HuT 78 cells, a malignant T cell, which express both 5 and 7TM VPAC1 isoforms. Levels of [cAMP]i were measured by a competitive ELISA after treating with increasing concentrations of VIP. Interesting, we show a VIP dependent decrease in [cAMP]i, suggesting that the 5TM VPAC1 isoform coexpressed in HuT 78 cells suppress 7 TM induced [cAMP]i levels. The ratio of the 5 and 7TM receptors on the cell membrane may explain the unique level of [cAMP]i upon VIP binding. Future studies will inhibit Gαi coupling with pertussis toxin and RNAi to knockdown the 5TM VPAC1 to measure [cAMP]i response evoked by the 7TM VPAC‐1 receptor in coexpressing cells. Research supported by NIH‐KO1 1KO1DK664828 and COBRE 2P20RR015566.