TorsinA negatively controls neurite outgrowth of SH-SY5Y human neuronal cell line

Early onset generalized dystonia is a severe form of primary dystonia linked to a mutation of the DYT1(TOR1A) gene on chromosome 9q34. DYT1 gene codifies for human torsinA, an AAA+ ATPase associated with the membranes of endoplasmic reticulum (ER) and the synaptic vesicles and proposed to be involved in trafficking of tubular-vesicular membrane through neuronal processes. In this study, the presence and the intracellular distribution of torsinA protein in SH-SY5Y neuroblastoma cells were evaluated by immunofluorescence and Western blot analysis following differentiation with retinoic acid and BDNF. Protein expression was then inhibited by transient antisense transfection and the possible effect on neurite outgrowth was observed. In SH-SY5Y cells torsinA, with an apparent MW of 38 kDa, is endogenously present and distributed, with a punctate pattern, in the cytosol and along the neurites. The protein showed high intensity of immunoreactivity in the neurite varicosities and was partially co-localized with vesicles markers. Terminally differentiated cells showed an increase of protein expression. Oligonucleotide antisense treatment induced a significant response to differentiating stimuli, lead to sprouting of longer neurites and increase in growth cone areas. A relationship between torsinA and tau protein, which is involved in axon elongation and establishment of neuronal polarity, was demonstrated by co-immunoprecipitation experiments. These findings suggest that torsinA, throughout the interaction with microtubule associated proteins, may contribute to control neurite outgrowth and could be involved in maintaining cell polarity. (C) 2004 Elsevier B.V. All rights reserved.