GTP‐binding proteins in luminal and basolateral membranes from pars convoluta and pars recta of rabbit kidney proximal tubule

Abstract

The GTP-binding proteins on luminal and basolateral membrane vesicles from outer cortex (pars convoluta) and outer medulla (pars recta) of rabbit proximal tubule have b~n examined. The membrane vesicles were highly purified, as ascertained by electron microscopy, by measurements of marker enzymes, and by investigating seganental-specifie transport systems. The [~SJGTP~,S binding to vesicles, and to sodium cholatc-cxtracted proteins from vesicles, indicated that the total content of GTP-binding proteins were equally distributed on pars convoluta, pars recta luminal and basolateral membranes. The m~mbranes were ADP-ribosylated with [~:P]NAD" in the presence of pertussis toxin and cholera toxin. Gel elec~ro-phoresis revealed, for all preparations, the presence of cholera toxin [~ZP]ADP.ribosylated 42 and 45 kDa Gct, proteins, and pertussis toxin [~:P]ADP-ribosylated 41 kDa G~, 40 kDa G0::. and 41 kDa G~ proteins. The 2D electrophoresis indicated that G,,'s were not present in luminal nor in basolateral membranes of pars convoluta or pars recta of rabbit proximal tubule. G-protein; Proximal tubule

P2 Receptor-mediated Inhibition of Vasopressin-stimulated Fluid Transport and cAMP Responses in AQP2-transfected MDCK Cells

“…It has been reported that activation of Gi protein might be an important target for several hormones and autacoids that antagonize the Gs protein-coupled effects of AVP. Gαi1, Gαi2 and Gαi3 are known to be present in the nephron cells (Buhl et al, 1992). It seems, therefore, very likely that these pertussis toxin-sensitive species constitute underlying desensitization mechanism of ATP-stimulated cAMP reponses.…”