Down-regulation of angiotensin II receptor subtypes and desensitization of cyclic GMP production in neuroblastoma N1E-115 cells.
Murine neuroblastoma N1E-115 cells possess membranous receptors for the octapeptide angiotensin II (AngII) whose density is substantially increased by in vitro differentiation. Incubation of differentiated N1E-115 cells with AngII produced a rapid decrease in receptor density, but did not alter the affinity of these receptors for either 125I-AngII or the high-affinity antagonist 125I-[Sarc1,Ile8]-AngII. This apparent down-regulation was dose related with an ED50 of 1 nM, and maximal decreases of approximately 90% were obtained with 100 nM AngII. Receptor loss from differentiated cell membranes was unaffected by incubations of membranes obtained from agonist-exposed cells with non-hydrolyzable analogues of GTP for 60 min at 37 degrees C to ensure dissociation of the ligand. Partial loss of AngII receptors was apparent within 5 min of agonist exposure, whereas maximal declines were not observed until 30 min. This temporal pattern resulted from a preferential decrease in the AT1 receptor subtype during the first 5 min, followed by a decline in both AT1 and AT2 receptors with longer periods of agonist exposure. The loss of membranous receptors was reversible with partial recovery observed after 4 h, and with nearly full recovery observed 18 h after exposure of the cells to AngII. However, the long-term recovery of receptor density was blocked by the protein synthesis inhibitor, cycloheximide. The heptapeptide angiotensin III produced a similar down-regulation of receptors, and the high-affinity antagonist [Sarc1,Thr8]-AngII blocked agonist-induced down-regulation. Finally, the apparent loss of cell surface AngII receptors decreased the ability of AngII to stimulate cyclic GMP production within intact N1E-115 cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104.
L P
LP
Reagan
X
X
Ye
C H
CH
Maretzski
S J
SJ
Fluharty
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D006152:Cyclic GMP / Q000096:biosynthesis*; D015536:Down-Regulation; D051379:Mice; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D011945:Receptors, Angiotensin / Q000145:classification / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors; D014407:Tumor Cells, Cultured
D011945:Receptors, Angiotensin; D000804:Angiotensin II; D006152:Cyclic GMP