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Retinoic Acid‐Induced Differentiation of Human Neuroblastoma SH‐SY5Y Cells Is Associated with Changes in the Abundance of G Proteins
Author(s) -
Ammer Hermann,
Schulz Rüdiger
Publication year - 1994
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1994.62041310.x
Subject(s) - sh sy5y , retinoic acid , neuroblastoma , abundance (ecology) , tretinoin , biology , chemistry , microbiology and biotechnology , biochemistry , genetics , ecology , cell culture , gene
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: Gaα, G i α1, G j α2, G c α, G z α, and Gβ. Differentiation of the cells by all‐ trans ‐retinoic acid (RA) treatment (10 μmol/L; 6 days) caused substantial alterations in the abundance of distinct G protein subunits. Concomitant with an enhanced expression of μ‐opioid binding sites, the levels of the inhibitory G proteins G i α1 and G j α1 were found to be significantly increased. This coordinate up‐reg‐ ulation is accompanied by functional changes in μ‐opioid receptor‐stimulated Iow‐ K m GTPase, μ‐receptor‐mediated adenylate cyclase inhibition, and receptor‐independent guanosine 5′‐(βγ‐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 prosta‐ glandin E 1 (PGE 1 ) receptors and G s α, the G protein subunit activating adenylate cyclase. RA treatment of SH‐SY5Y cells increases both the number of PGE 1 binding sites and PGE 1 stimulated adenylate cyclase activity, but significantly reduced amounts of G z α were found. This down‐ regulation is paralleled by a decrease in the stimulatory activity of G z α as assessed in S49 cyc ‐ reconstitution assays. However, the reduction in G a α levels had no effect on both intrinsic and receptor‐independent‐activated [Gpp(NH)p or forskolin; 100 μtmol/L each] adenylate cyclase, suggesting that the amount of G z α is in excess over the functional capacity of adenylate cyclase in SH‐SY5Y cell membranes. Additional quantitative changes were found for G z α, G c α, and Gβ subunits. In contrast, neuronal differentiation in the presence of 12‐O‐tetradecanoylphor‐ bol 13‐acetate (16 nmol/L; 6 days) failed to affect G protein abundance. Our results provide evidence for a specific RA effect on the abundance of distinct G protein sub‐ units in human SH‐SY5Y neuroblastoma cells. These alterations might contribute to functional changes in transmembrane signaling pathways associated with RA‐in‐ duced neuronal differentiation of the cells.