Regulation of Chka expression during RA-induced neuronal differentiation.

DOMIZI, P. AND BANCHIO, C.

Ciudad Autonoma de Buenos Aires

Congreso; 2º Simposio Franco-Argentino de Neurociencias.; 2012

Neuritogenesis is a dynamic process, involving the extension of long protrusions called neurites, and is critically dependent on membrane biosynthesis. As Phosphatidylcholine (PtdCho) is the major phospholipid building block of membranes, its biosynthesis is coordinately regulated during neuronal differentiation. We demonstrated that during Retinoic acid (RA) induced differentiation of Neuro-2a cells, PtdCho biosynthesis is induced by enhanced expression of the Chka gene, which encoded Choline Kinase alpha, the first enzyme in the CDP-choline pathway. Choline Kinase is a critical enzyme as it conducts the choline entering the cell toward the synthesis of new PtdCho, in detriment of the production of the neurotransmitter acetylcholine. Taking into account that neurite outgrowth is important for neuronal plasticity as well as for neuronal regeneration after injuries or neuropathological conditions; we are interested in understanding the mechanism by which RA induces the expression of Chka gene. Using promoter reporter assay, electromobility gel shift assay, analysis of point mutations and overexpression of different transcription factors we demonstrated that the region between -953 and -901 bp of Ckha promoter is essential for RA induction. This region contains two C/EBP and Egr binding sites which are implicated in Chka transcriptional induction. We demonstrated that C/EBPb overexpression promote Chka expression and stimulates neuronal differentiation even in the absence of RA, and we also observed that Egr is necessary for Chka response to RA. In summary, these results suggest that Chka regulation by RA is a complex mechanism in which the transcription factors C/EBPb and Egr participate together to induce expression of Chka.