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J. Biol. Chem., Vol. 265, Issue 8, 4218-4222, 03, 1990
I Teitelbaum
Studies were performed to examine a potential role for a guanine
nucleotide-binding protein in epidermal growth factor (EGF)-stimulated
phospholipase A2 (PLA2) activity. EGF increased prostaglandin E2 (PGE2)
production in intact or saponin-permeabilized rat inner medullary
collecting tubule (RIMCT) cells. Incubation of permeabilized cells with
guanosine 5'-O-(thiotriphosphate) (GTP gamma S) enhanced and with guanosine
5'-O-(2-thiodiphosphate) (GDP beta S) inhibited the response to EGF. GDP
beta S had no effect on ionomycin-stimulated PGE2 production. Exposure of
intact cells to 25 mM NaF + 10 microM AlCl3 enhanced both basal and
EGF-stimulated PGE2 production. Pertussis toxin ADP-ribosylated a 41-kDa
protein in RIMCT cell membranes. Pretreatment of cells with pertussis toxin
(100 ng/ml for 16 h) eliminated the response to EGF in intact cells and the
response to EGF + GTP gamma S in permeabilized cells. Pertussis toxin had
no effect on the response to ionomycin. The effect of pertussis toxin was
not due to alterations in cAMP as cellular cAMP levels were unaffected by
pertussis toxin both in the basal state and in the presence of EGF. PGE2
production in response to EGF was not transduced by a G protein coupled to
phospholipase C (PLC) as neomycin, which inhibited PLC, did not decrease
EGF-stimulated PGE2 production. Also, PGE2 production was not increased by
inositol trisphosphate and did not require the presence of extracellular
Ca2+. In contrast to EGF-stimulated PLC activity, stimulation of PLA2 by
EGF was not susceptible to inhibition by phorbol 12-myristate 13-acetate.
These results clearly demonstrate the existence of a PLA2-specific
pertussis toxin-inhibitable guanine nucleotide-binding protein coupled to
the EGF receptor in RIMCT cells.
The epidermal growth factor receptor is coupled to a phospholipase A2- specific pertussis toxin-inhibitable guanine nucleotide-binding regulatory protein in cultured rat inner medullary collecting tubule cells
Department of Medicine, University of Colorado School of Medicine, Denver 80262.
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