Glucose-dependent insulinotropic polypeptide-mediated signaling pathways enhance apical PepT1 expression in intestinal epithelial cells
| Autor: | John H. Schwartz, Steven Coon, Satish K. Singh, Vazhaikkurichi M. Rajendran |
|---|---|
| Rok vydání: | 2015 |
| Předmět: |
medicine.medical_specialty
Physiology Hormones and Signaling Gastric Inhibitory Polypeptide Transfection Peptide Transporter 1 Intestinal absorption Cell Line Receptors Gastrointestinal Hormone Wortmannin chemistry.chemical_compound Physiology (medical) Internal medicine Cyclic AMP medicine Animals Guanine Nucleotide Exchange Factors Intestinal Mucosa Protein Kinase Inhibitors Protein kinase B PI3K/AKT/mTOR pathway Protein kinase C Phosphoinositide-3 Kinase Inhibitors Homeodomain Proteins Dose-Response Relationship Drug Symporters Hepatology biology Peptide transporter 1 Gastroenterology Epithelial Cells Dipeptides Apical membrane Molecular biology Rats Up-Regulation Intestines Protein Transport Endocrinology Calphostin C Intestinal Absorption chemistry biology.protein Phosphatidylinositol 3-Kinase Proto-Oncogene Proteins c-akt hormones hormone substitutes and hormone antagonists Signal Transduction |
| Zdroj: | American Journal of Physiology-Gastrointestinal and Liver Physiology. 308:G56-G62 |
| ISSN: | 1522-1547 0193-1857 |
| DOI: | 10.1152/ajpgi.00168.2014 |
| Popis: | We have shown recently that glucose-dependent insulinotropic polypeptide (GIP), but not glucagon-like peptide 1 (GLP-1) augments H+ peptide cotransporter (PepT1)-mediated peptide absorption in murine jejunum. While we observed that inhibiting cAMP production decreased this augmentation of PepT1 activity by GIP, it was unclear whether PKA and/or other regulators of cAMP signaling pathway(s) were involved. This study utilized tritiated glycyl-sarcosine [3H-glycyl-sarcosine (Gly-Sar), a relatively nonhydrolyzable dipeptide] uptake to measure PepT1 activity in CDX2-transfected IEC-6 (IEC-6/CDX2) cells, an absorptive intestinal epithelial cell model. Similar to our earlier observations with mouse jejunum, GIP but not GLP-1 augmented Gly-Sar uptake (control vs. +GIP: 154 ± 22 vs. 454 ± 39 pmol/mg protein; P < 0.001) in IEC-6/CDX2 cells. Rp-cAMP (a PKA inhibitor) and wortmannin [phosophoinositide-3-kinase (PI3K) inhibitor] pretreatment completely blocked, whereas neither calphostin C (a potent PKC inhibitor) nor BAPTA (an intracellular Ca2+ chelator) pretreatment affected the GIP-augmented Gly-Sar uptake in IEC-6/CDX2 cells. The downstream metabolites Epac (control vs. Epac agonist: 287 ± 22 vs. 711 ± 80 pmol/mg protein) and AKT (control vs. AKT inhibitor: 720 ± 50 vs. 75 ± 19 pmol/mg protein) were shown to be involved in GIP-augmented PepT1 activity as well. Western blot analyses revealed that both GIP and Epac agonist pretreatment enhance the PepT1 expression on the apical membranes, which is completely blocked by wortmannin in IEC-6/CDX2 cells. These observations demonstrate that both cAMP and PI3K signaling pathways augment GIP-induced peptide uptake through Epac and AKT-mediated pathways in intestinal epithelial cells, respectively. In addition, these observations also indicate that both Epac and AKT-mediated signaling pathways increase apical membrane expression of PepT1 in intestinal absorptive epithelial cells. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|