Proximal tubular epithelial cells possess a novel 42-kilodalton guanine nucleotide-binding regulatory protein.
The proximal tubule of the kidney represents an important location where adenylate cyclase regulates salt and water transport; yet a detailed characterization of the distribution and classification of guanine nucleotide-binding protein (G protein) and adenylate cyclase is lacking. We used purified brush border (20-fold) and basolateral membranes (14-fold) to characterize parathyroid hormone- and G protein-regulated adenylate cyclase and G-protein distribution. Adenylate cyclase was predominantly localized to basolateral membranes, while the 46-kDa alpha subunit of the stimulatory G protein (Gs) was 2-fold higher in brush border membranes than in basolateral membranes. The alpha subunit of the inhibitory G protein (Gi; 41 kDa) was equally distributed on immunoblotting but was 2-fold higher in brush border membranes than in basolateral membranes on radiolabeling with pertussis toxin. A 42-kDa cholera toxin substrate that cross-reacted with antisera to the common alpha subunit of G proteins and to Gs on immunoblotting and that was not immunoprecipitated with two Gi antisera was the most abundant alpha subunit and comprised approximately 1% of the total membrane proteins. These observations suggest that G proteins are important regulators of proximal tubular transport independent of adenylate cyclase.
Zhou
J
J
Department of Medicine, Case Western Reserve University, Cleveland, OH.
Sims
C
C
Chang
C H
CH
Berti-Mattera
L
L
Hopfer
U
U
Douglas
J
J
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D037361:Adenylate Cyclase Toxin; D000535:Aluminum / Q000494:pharmacology; D017607:Aluminum Compounds; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism; D005459:Fluorides; D005461:Fluorine / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000378:metabolism; D008970:Molecular Weight; D009243:NAD / Q000378:metabolism; D010281:Parathyroid Hormone / Q000494:pharmacology; D037342:Pertussis Toxin; D011817:Rabbits; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D017607:Aluminum Compounds; D010281:Parathyroid Hormone; D010566:Virulence Factors, Bordetella; D009243:NAD; D005576:Colforsin; D000246:Adenosine Diphosphate Ribose; C050992:tetrafluoroaluminate; D005461:Fluorine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002772:Cholera Toxin; D000535:Aluminum; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D005459:Fluorides