Regulation of renal cortical Na-HCO3 cotransporter. II. Role of G proteins.
We examined the regulation of the renal cortical basolateral Na-HCO3 cotransporter by G proteins. Na-HCO3 cotransporter activity was measured in highly purified rabbit renal cortical basolateral membranes (BLMV) as the difference in 22Na uptake in presence of HCO3- and gluconate. HCO(3-)-dependent 22Na uptake was significantly inhibited by 10 microM guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), a G protein activator. In contrast, addition of 50 microM guanosine 5'-O-(2-thiodiphosphate) (GDP beta S), an inhibitor of G protein, prevented the inhibition of the Na-HCO3 cotransporter activity by GTP gamma S. AlF4-, another G protein activator, also inhibited the activity of the Na-HCO3 cotransporter. This inhibitory effect of G protein on the Na-HCO3 cotransporter activity was not prevented by dideoxyadenosine, an adenylate cyclase inhibitor, or by the protein kinase A inhibitor, suggesting a direct effect of G protein on the cotransporter. To identify the G proteins that mediate the regulation of the Na-HCO3 cotransporter, purified BLMV were ADP ribosylated in presence of cholera toxin or pertussis toxin. Autoradiograms of BLMV incubated with [32P]NAD showed that cholera and pertussis toxins caused ADP ribosylation of 42- and 41-kDa G proteins, respectively. To determine whether the ADP ribosylation by cholera or pertussis toxin was associated with alterations of the Na-HCO3 cotransporter activity, we measured HCO(3-)-dependent 22Na uptake in BLMV treated with 20 micrograms/ml cholera toxin or with 100 ng/ml pertussis toxin. Na-HCO3 cotransporter activity was significantly decreased by both cholera and pertussis toxins.(ABSTRACT TRUNCATED AT 250 WORDS)
Ruiz
O S
OS
Section of Nephrology, University of Illinois at Chicago.
Qiu
Y Y
YY
Wang
L J
LJ
Arruda
J A
JA
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D037361:Adenylate Cyclase Toxin; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002772:Cholera Toxin / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism*; D037342:Pertussis Toxin; D011487:Protein Conformation; D011817:Rabbits; D012964:Sodium / Q000378:metabolism; D027982:Sodium-Bicarbonate Symporters; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D001639:Bicarbonates; D002352:Carrier Proteins; D027982:Sodium-Bicarbonate Symporters; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002772:Cholera Toxin; D012964:Sodium; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins