Nitric oxide negatively regulates proliferation and promotes neuronal differentiation through N-Myc downregulation.
Nitric oxide (NO) has been found to act as an important negative regulator of cell proliferation in several systems. We report here that NO negatively regulates proliferation of neuronal cell precursors and promotes their differentiation by downregulating the oncogene N-Myc. We have studied this regulatory function of NO in neuroblastoma cell lines (SK-N-BE) and in primary cerebellar granule cell cultures. In a neuronal NO synthase (nNOS) overexpressing neuroblastoma cell line exposed to the differentiative action of retinoic acid, NO slowed down proliferation and accelerated differentiation towards a neuronal phenotype. This effect was accompanied by a parallel decrease of N-Myc expression. Similar results could be obtained in parental SK-N-BE cells by providing an exogenous source of NO. Pharmacological controls demonstrated that NO's regulatory actions on cell proliferation and N-Myc expression were mediated by cGMP as an intermediate messenger. Furthermore, NO was found to modulate the transcriptional activity of N-Myc gene promoter by acting on the E2F regulatory region, possibly through the control of Rb phosphorylation state, that we found to be negatively regulated by NO. In cerebellar granule cell cultures, NOS inhibition increased the division rate of neuronal precursors, in parallel with augmented N-Myc expression. Because a high N-Myc expression level is essential for neuroblastoma progression as well as for proliferation of neuronal precursors, its negative regulation by NO highlights a novel physiopathological function of this important messenger molecule.
Department of Human and General Physiology, University of Bologna, Piazza di Porta San Donato 2, 40127, Bologna, Italy. eciani@alma.unibo.it
Elisabetta
E
Ciani
Sabina
S
Severi
Andrea
A
Contestabile
Renata
R
Bartesaghi
Antonio
A
Contestabile
D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D015536:Down-Regulation; D005786:Gene Expression Regulation; D016259:Genes, myc; D006801:Humans; D019331:NG-Nitroarginine Methyl Ester / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D009447:Neuroblastoma; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D011401:Promoter Regions, Genetic; D051381:Rats; D017208:Rats, Wistar; D016160:Retinoblastoma Protein / Q000378:metabolism; D014158:Transcription, Genetic; D014212:Tretinoin / Q000494:pharmacology
D009419:Nerve Tissue Proteins; D016160:Retinoblastoma Protein; D009569:Nitric Oxide; D014212:Tretinoin; C496320:NOS1 protein, human; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D006152:Cyclic GMP; D019331:NG-Nitroarginine Methyl Ester