Retinoic acid-induced differentiation of human neuroblastoma SH-SY5Y cells is associated with changes in the abundance of G proteins.
Western blot analysis, using subtype-specific anti-G protein antibodies, revealed the presence of the following G protein subunits in human neuroblastoma SH-SY5Y cells: Gs alpha, Gi alpha 1, Gi alpha 2, Go alpha, Gz alpha, and G beta. Differentiation of the cells by all-trans-retinoic acid (RA) treatment (10 mumol/L; 6 days) caused substantial alterations in the abundance of distinct G protein subunits. Concomitant with an enhanced expression of mu-opioid binding sites, the levels of the inhibitory G proteins Gi alpha 1 and Gi alpha 2 were found to be significantly increased. This coordinate up-regulation is accompanied by functional changes in mu-opioid receptor-stimulated low-Km GTPase, mu-receptor-mediated adenylate cyclase inhibition, and receptor-independent guanosine 5'-(beta gamma-imido)triphosphate [Gpp(NH)p; 10 nmol/L]-mediated attenuation of adenylate cyclase activity. In contrast, increased levels of inhibitory G proteins had no effect on muscarinic cholinergic receptor-mediated adenylate cyclase inhibition. With respect to stimulatory receptor systems, a reciprocal regulation was observed for prostaglandin E1 (PGE1) receptors and Gs alpha, the G protein subunit activating adenylate cyclase. RA treatment of SH-SY5Y cells increases both the number of PGE1 binding sites and PGE1-stimulated adenylate cyclase activity, but significantly reduced amounts of Gs alpha were found. This down-regulation is paralleled by a decrease in the stimulatory activity of Gs alpha as assessed in S49 cyc- reconstitution assays.(ABSTRACT TRUNCATED AT 250 WORDS)
Ammer
H
H
Institute of Pharmacology, Toxicology and Pharmacy, University of Munich, München, F.R.G.
Schulz
R
R
D000262:Adenylyl Cyclases / Q000378:metabolism; D000527:Alprostadil / Q000378:metabolism; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D009447:Neuroblastoma / Q000378:metabolism / Q000473:pathology*; D017450:Receptors, Opioid, mu / Q000187:drug effects / Q000502:physiology; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D017450:Receptors, Opioid, mu; D006165:Guanylyl Imidodiphosphate; D014212:Tretinoin; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D000527:Alprostadil