Involvement of nm23-M2 in dopaminergic neuronal differentiation and cell cycle arrest

Abstract

Nm23 genes which encode nucleoside diphosphate kinases are ubiquitous metabolic enzymes, responsible for the synthesis of nonadenine nucleoside triphosphates from the corresponding diphosphates, with ATP as phosphoryl donor. In our previous study, nm23-M2 was one of the candidate genes which was found to be up-regulated upon n-butyric acid-induced MN9D differentiation through subtractive library screening and micro-array analysis. This study aims to elucidate the role of nm23-M2 in dopaminergic neuronal differentiation. Overexpression of nm23-M2 in MN9D cell line resulted in significant increase in the number of cells bearing neurites and an alteration of the cell cycle, increased G1-phase. Analysis of immunoblots revealed that this morphological differentiation was accompanied by increased expression of a marker of maturation, synaptosomal protein SNAP-25 and decreased expression of a cell cycle marker, cyclin D1. n-butyric acid-induced neurite outgrowth in MN9D cells was also abolished by nm23-M2 siRNA treatment and the level of SNAP-25 and cyclin D1 remained unaltered by siRNA interference. These data support the idea that nm23-M2 plays a role in dopaminergic neuronal differentiation.