Friday 27 January 2006
SPG7 encodes a nuclear-encoded mitochondrial metalloprotease protein termed paraplegin.
germline SPG7 mutations in SPG7-associated hereditary spastic paraplegia
- autosomal recessive hereditary pure spastic paraplegia
- linkage and subsequent mutation analysis revealed large deletions in SPG7
Muscle biopsies from the autosomal recessive form of patients with hereditary spastic paraplegia revealed histochemical signs of a mitochondrial disorder, namely RRFs, COX-negative fibres and succinate dehydrogenase-positive hyperintense fibres.
Owing to the homology with a yeast mitochondrial ATPase with both proteolytic and chaperone-like activities, it has been suggested that this form of hereditary spastic paraplegia could be a neurodegenerative disorder due to OXPHOS deficiency, attributing a putative function in the assembly or import of respiratory chain subunits or cofactors to paraplegin.
An autosomal recessive form of the disease is caused by mutations in paraplegin, which is a conserved subunit of the ubiquitous and ATP-dependent m-AAA protease in mitochondria.
The m-AAA protease carries out protein quality control in the inner membrane of the mitochondria, suggesting a pathogenic role of misfolded proteins in HSP.
The m-AAA protease regulates ribosome assembly and translation within mitochondria by controlling proteolytic maturation of a ribosomal subunit. Here, we will discuss implications of the dual role of the m-AAA protease in protein activation and degradation for mitochondrial dysfunction and axonal degeneration.
hereditary spastic paraplegias
- SPG7-associated hereditary spastic paraplegia