14-3-3 proteins and spinocerebellar ataxia type 1: from molecular interaction to human neuropathology.

This mini-review focuses on the possible relevance of 14-3-3 proteins in spinocerebellar ataxia type 1 (SCA1). 14-3-3 proteins are mainly localized in the synapses and neuronal cytoplasm, and seven isoforms have been identified in mammals. This family of proteins was initially identified as adaptor proteins which bind to phosphoserine-containing motifs. Binding motifs and potential functions of 14-3-3 proteins are now recognized to have a wide range of functional relevance. SCA1 is an autosomal-dominant neurodegenerative disorder and is linked to polyglutamine expansion (ataxin-1 protein). The Zoghbi and Orr group showed direct interaction of 14-3-3 proteins with ataxin-1 where nuclear recruitment of the ataxin-1 protein is dependent on its phosphorylation. This targeted binding of 14-3-3 protein to phosphorylated ataxin-1 to stabilize ataxin-1 in cellular models was corroborated by our double-labeling study for expanded polyglutamine and 14-3-3 proteins which demonstrated colocalization of these two epitopes in the neuronal nuclei in human autopsied brains with SCA1. Ataxin-1/14-3-3 protein interaction is a new potential target for therapeutic intervention in the treatment of SCA1.