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GIP Regulates Pept1 via Akt and EPAC Signaling Pathways in Intestinal Epithelial Cells
Author(s) -
Coon Steven,
Schwartz John,
Singh Satish
Publication year - 2013
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.27.1_supplement.1162.3
Subject(s) - protein kinase b , signal transduction , incretin , medicine , endocrinology , chemistry , protein kinase a , g protein coupled receptor , phosphorylation , microbiology and biotechnology , kinase , biology , diabetes mellitus , type 2 diabetes
Background GIP, an incretin hormone, is important in the pathogenesis of obesity and diabetes. GIP increases dipeptide transport in both murine jejunum and intestinal cells grown in vitro. GIP activates both the cAMP and PI3 kinase pathways but the mechanism and intermediates involved in Pept1 regulation are not known. Objective To elucidate the intracellular signaling pathways that regulate GIP‐stimulated dipeptide transport. Methods Transport and signaling pathways for GIP were determined by growing IEC6 cells on filter inserts and measuring Pept1 uptake. 3 H‐GlySar (50 uM) and GIP (100 nM ) were added to the apical and basolateral side, respectively. Results Akt inhibitor 3 which inhibits Akt, a downstream intermediate of the PI3 kinase pathway, decreased Pept1 activity by 75% (110±10 compared to 486±39 pmol/min/mg‐protein for GIP stimulated control). To probe the cAMP pathway, we found that the EPAC agonist (8‐pCPT‐2′‐O‐Me‐cAMP‐AM, 20 nM) increased Pept1 activity (520±41 pmol/min/mg‐protein) while a PKA agonist (8‐brcAMP, 50 nM) failed to increase Pept1 activity when compared to untreated (no GIP) control (240±39 pmol/min/mg‐protein). Western blots documented significant increases in apical expression of Pept1 upon GIP stimulation. Conclusion GIP augmented Pept1 transport is consistent with a model where membrane targeting of the protein is induced by Akt and via EPAC activation by cAMP.