Protein kinase C-dependent and -independent activation of Na+/H+ exchanger by G alpha 12 class of G proteins.
Constitutively activated mutants of the G alpha 12 class of G proteins, G alpha 12(Q229L) and G alpha 13(Q226L), were transiently expressed in COS-1 cells, and the activity of amiloride-sensitive Na+/H+ exchanger was measured. The expression of either G alpha 12(Q229L) or G alpha 13(Q226L) increased the basal activity of the amiloride-sensitive exchanger by 2-5-fold. Regulation of this activation by other G protein signaling pathways was investigated by the transient expression of constitutively activated G protein mutants of G alpha s(Q227L), G alpha i2(Q205L), and G alpha q(Q209L) in COS-1 cells. Only G alpha q showed a similar activation of the exchanger. Chronic treatment of the transfected cells with 4 beta-phorbol 12-myristate 13-acetate to deplete the endogenous protein kinase C completely inhibited the activation of the antiporter by G alpha 12(Q229L), whereas activation by G alpha 13(Q226L) remained unaffected. These results indicated that both G alpha 12 and G alpha 13 can activate Na+/H+ exchanger by two distinct signaling pathways. G alpha 12 activation of the exchanger was dependent on protein kinase C pathway, whereas G alpha 13 activation was not. These studies define the involvement of G alpha 12 class of G proteins, for which no function has been assigned yet, in the activation of Na+/H+ exchanger.
Dhanasekaran
N
N
Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
Prasad
M V
MV
Wadsworth
S J
SJ
Dermott
J M
JM
van Rossum
G
G
D000584:Amiloride / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D015342:DNA Probes; D005452:Fluoresceins; D005456:Fluorescent Dyes; D019204:GTP-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011493:Protein Kinase C / Q000378:metabolism*; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
D015342:DNA Probes; D005452:Fluoresceins; D005456:Fluorescent Dyes; D017923:Sodium-Hydrogen Exchangers; C057433:2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester; D000584:Amiloride; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate