1. ¹Unidad de Investigación, Hospital Universitario de Salamanca, Instituto de Estudios de Ciencias de la Salud de Castilla y León, Salamanca, Spain
2. ²Departamento de Bioquímica y Biología Molecular, Instituto de Neurociencias de Castilla y León, Universidad de Salamanca, Salamanca, Spain
3. ³Instituto de Biología Molecular y Celular del Cancer, Consejo Superior de Investigaciones Científicas, Universidad de Salamanca, Salamanca, Spain

Correspondence: Dr A Almeida, Unidad de Investigación, Hospital Universitario de Salamanca, Instituto de Estudios de Ciencias de la Salud de Castilla y León, Paseo San Vicente, 58-182, Salamanca 37007, Spain. E-mail: aaparra@usal.es

Received 26 July 2007; Revised 19 October 2007; Accepted 14 November 2007; Published online 21 January 2008.

Abstract

In neuroblastoma cells, retinoic acid induces cell cycle arrest and differentiation through degradation of the F-box protein, Skp2, and stabilization of cyclin-dependent kinase inhibitor, p27. However, the mechanism responsible for retinoic acid-mediated Skp2 destabilization is unknown. Since Skp2 is degraded by anaphase-promoting complex (APC)^Cdh1, here we studied whether retinoic acid promotes differentiation of human SH-SY5Y neuroblastoma cells by modulating Cdh1. We found that retinoic acid induced the nuclear accumulation of Cdh1 that paralleled Skp2 destabilization and p27 accumulation. The mRNA and protein abundance of Rae1—a nuclear export factor that limits APC^Cdh1 activity in mitosis—decreased upon retinoic acid-induced inhibition of neuroblastoma cell proliferation. Furthermore, either Rae1 overexpression or Cdh1 inhibition promoted Skp2 accumulation, p27 destabilization and prevented retinoic acid-induced cell cycle arrest and differentiation. Conversely, inhibition of Rae1 accelerated retinoic acid-induced differentiation. Thus, retinoic acid downregulates Rae1, hence facilitating APC^Cdh1-mediated Skp2 degradation leading to the arrest of cell cycle progression and neuroblastoma differentiation.