Influence of cyclic AMP and serum factors upon expression of a retinoid-responsive gene in neuroblastoma cells.
Cyclic AMP can profoundly influence the growth and differentiation of neuronal cells in culture. In this study, the relationship between this second messenger signal transduction pathway, cell differentiation, and the expression of a retinoid-responsive, thymosin beta-10 gene was examined. Thymosin beta-10 and cognate mRNA were expressed at high levels in actively proliferating rat B104 neuroblastoma cells cultured in medium containing 10% FCS. These cells were induced to differentiate in the presence of the cAMP analog N6, 2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (Bt2-cAMP) (1 mM) and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) (100 microM). Expression of thymosin beta-10 mRNA was markedly inhibited (greater than 90% and 70%, respectively) by these compounds. Addition of sodium butyrate (NaB, 1 mM) indicated that at least part of the inhibitory actions of Bt2-cAMP were due to esterase-induced release of butyrate from this compound. Adenosine (50 microM), a metabolic precursor to endogenous cyclic AMP, also inhibited accumulation of thymosin beta-10 mRNA (to less than 70% of control levels). The inhibitory action of Bt2-cAMP upon thymosin beta-10 mRNA levels was time dependent; levels were inhibited by greater than 50% 24 hours after addition of the cAMP analog and by greater than 90% after 72 hours. Serum starvation (0.2% FCS for seven days) provoked a marked increase in neurite out-growth; this morphological change was also accompanied by a modest inhibition of thymosin beta-10 mRNA accumulation. These findings together with previous observations imply that both cyclic AMP-dependent and retinoid-responsive mechanisms coordinate thymosin beta-10 gene expression during neuroembryogenesis.
Hall
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Department of Surgery, University of Medicine and Dentistry, New Jersey Medical School, Newark 07103-2757.
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001790:Blood Physiological Phenomena; D003994:Bucladesine / Q000494:pharmacology; D002087:Butyrates / Q000494:pharmacology; D020148:Butyric Acid; D002454:Cell Differentiation / Q000187:drug effects; D002772:Cholera Toxin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D004247:DNA / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D015994:Incidence; D008969:Molecular Sequence Data; D009447:Neuroblastoma / Q000453:epidemiology / Q000473:pathology*; D051381:Rats; D012176:Retinoids / Q000494:pharmacology*; D015290:Second Messenger Systems; D013947:Thymosin / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000473:pathology
D002087:Butyrates; D012176:Retinoids; D020148:Butyric Acid; D013947:Thymosin; D003994:Bucladesine; C039302:thymosin beta(10); D004247:DNA; D002772:Cholera Toxin; D000242:Cyclic AMP; D000241:Adenosine; D015056:1-Methyl-3-isobutylxanthine