HORMONAL-REGULATION OF MAP KINASE IN CULTURED RAT INNER MEDULLARY COLLECTING TUBULE CELLS

Citation
Le. Heasley et al., HORMONAL-REGULATION OF MAP KINASE IN CULTURED RAT INNER MEDULLARY COLLECTING TUBULE CELLS, The American journal of physiology, 267(3), 1994, pp. 60000366-60000373
Citations number
22
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physiology
ISSN journal
0002-9513
Volume
267
Issue
3
Year of publication
1994
Part
2
Pages
60000366 - 60000373
Database
ISI
SICI code
0002-9513(1994)267:3<60000366:HOMKIC>2.0.ZU;2-Q
Abstract
Mitogen-activated protein (MAP) kinase is a widely expressed protein s erine/threonine kinase that serves as a convergence point for many sig naling pathways including receptor tyrosine kinases, G protein-coupled receptors, and protein kinase C (PKC). The hormonal regulation of MAP kinase was studied in cultured established rat inner medullary collec ting tubule (RIMCT) cells. Neither vasopressin nor beta-adrenergic ago nists stimulated MAP kinase, despite clear stimulation of adenosine 3' ,5'-cyclic monophosphate (cAMP)-dependent protein kinase. In contrast, carbachol, ATP, and epidermal growth factor (EGF), which are known to antagonize vasopressin action in the RIMCT, stimulated the MAP kinase pathway. This stimulation was mimicked by the phorbol ester, 12-O-tet radecanoylphorbol-13-acetate, which directly activates PKC. The potenc y with which EGF and carbachol activated MAP kinase was similar to the potency with which they inhibited vasopressin-stimulated cAMP accumul ation. To assess the role of G(i) proteins in these stimulatory events , RIMCT cells were pretreated with pertussis toxin to inhibit G(i)-med iated signaling. Pertussis toxin did not influence ATP- or EGF-stimula ted MAP kinase, but completely inhibited carbachol stimulation, sugges ting that G(i) proteins mediate muscarinic stimulation. Prolonged expo sure of RIMCT cells to high phorbol ester concentrations to downregula te PKC ablated carbachol- and ATP-stimulated MAP kinase, but not EGF-s timulated MAP kinase, suggesting that PKC is a component of the networ k involved in MAP kinase activation by purinergic and muscarinic agoni sts. Investigation of the sidedness of the hormonal stimulations indic ated that EGF-stimulated MAP kinase was highly polarized, occurring ex clusively from the basolateral surface, whereas carbachol stimulated M AP kinase similarly from either cell surface. Thus EGF, ATP, and carba chol, three hormones that negatively influence vasopressin-stimulated water transport in the collecting duct, signal MAP kinase activation t hrough distinct mechanisms. The findings highlight the MAP kinases and their upstream activators as a potential pathway, in addition to PKC, involved in hormonal regulation of vasopressin action in the collecti ng duct.