Spastin recovery in hereditary spastic paraplegia by preventing neddylation-dependent degradation

ABSTRACT: Hereditary Spastic Paraplegia (HSP) is a neurodegenerative disease most commonly caused by autosomal dominant mutations in the SPG4 gene encoding the microtubule severing protein spastin. We hypothesise that SPG4-HSP is attributable to reduced spastin function due to haploinsufficiency, thus therapeutic approaches which elevate levels of the wild type spastin allele may be an effective therapy. However until now, how spastin levels are regulated is largely unknown. Here, we show that the kinase HIPK2 regulates spastin protein levels in proliferating cells, in differentiated neurons and in vivo. Our work reveals that HIPK2-mediated phosphorylation of spastin at S268 inhibits spastin K48-poly-ubiquitination at K554 and prevents its neddylation-dependent proteasomal degradation. In a spastin RNAi neuronal cell model, overexpression of HIPK2, or inhibition of neddylation, restores spastin levels and rescues neurite defects. Notably, we demonstrate that spastin levels can be restored pharmacologically by inhibiting its neddylation-mediated degradation in neurons derived from a spastin mouse model of HSP and in patient derived cells, thus revealing novel therapeutic targets for the treatment of SPG4-HSP. We do not know how S268 phosphorylation prevents spastin ubiquitination at K554; we hypothesised that phosphorylation can protect spastin from polyubiquitination by impairing the recruitment of proteins belonging to ubiquitination pathway or by promoting the interactions with factors that mask spastin region necessary for efficient ubiquitination/degradation. To have insight about these hypotheses, we analysed by mass spectrometry (MS) the interactome of spastin-S268A and -S268D upon overexpression in HeLa cells.

INSTRUMENT(S): LTQ

ORGANISM(S): Homo Sapiens (human) Bos Taurus (bovine)

TISSUE(S): Cell Culture

SUBMITTER: Marialuisa Casella  

LAB HEAD: Marco Crescenzi

PROVIDER: PXD021945 | Pride | 2020-10-22

REPOSITORIES: Pride