Vasopressin-mediated mitogenic signaling in intestinal epithelial cells.

The role of G protein-coupled receptors and their ligands in intestinal epithelial cell signaling and proliferation is poorly understood. Here, we demonstrate that arginine vasopressin (AVP) induces multiple intracellular signal transduction pathways in rat intestinal epithelial IEC-18 cells via a V_1A receptor. Addition of AVP to these cells induces a rapid and transient increase in cytosolic Ca²⁺ concentration and promotes protein kinase D (PKD) activation through a protein kinase C (PKC)-dependent pathway, as revealed by in vitro kinase assays and immunoblotting with an antibody that recognizes autophosphorylated PKD at Ser⁹¹⁶. AVP also stimulates the tyrosine phosphorylation of the nonreceptor tyrosine kinase proline-rich tyrosine kinase 2 (Pyk2) and promotes Src family kinase phosphorylation at Tyr⁴¹⁸, indicative of Src activation. AVP induces extracellular signal-related kinase (ERK)-1 (p44^mapk) and ERK-2 (p42^mapk) activation, a response prevented by treatment with mitogen-activated protein kinase kinase (MEK) inhibitors (PD-98059 and U-0126), specific PKC inhibitors (GF-I and Ro-31-8220), depletion of Ca²⁺ (EGTA and thapsigargin), selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (tyrphostin AG-1478, compound 56), or the selective Src family kinase inhibitor PP-2. Furthermore, AVP acts as a potent growth factor for IEC-18 cells, inducing DNA synthesis and cell proliferation through ERK-, Ca²⁺-, PKC-, EGFR tyrosine kinase-, and Src-dependent pathways. [ABSTRACT FROM AUTHOR]