3 research outputs found
The Hsp60-(p.V98I) Mutation Associated with Hereditary Spastic Paraplegia SPG13 Compromises Chaperonin Function Both in Vitro and in Vivo*Sâ
We have previously reported the association of a mutation (c.292G >
A/p.V98I) in the human HSPD1 gene that encodes the mitochondrial
Hsp60 chaperonin with a dominantly inherited form of hereditary spastic
paraplegia. Here, we show that the purified Hsp60-(p.V98I) chaperonin displays
decreased ATPase activity and exhibits a strongly reduced capacity to promote
folding of denatured malate dehydrogenase in vitro. To test its
in vivo functions, we engineered a bacterial model system that lacks
the endogenous chaperonin genes and harbors two plasmids carrying
differentially inducible operons with human Hsp10 and wild-type Hsp60 or Hsp10
and Hsp60-(p.V98I), respectively. Ten hours after shutdown of the wild-type
chaperonin operon and induction of the Hsp60-(p.V98I)/Hsp10 mutant operon,
bacterial cell growth was strongly inhibited. No globally increased protein
aggregation was observed, and microarray analyses showed that a number of
genes involved in metabolic pathways, some of which are essential for robust
aerobic growth, were strongly up-regulated in Hsp60-(p.V98I)-expressing
bacteria, suggesting that the growth arrest was caused by defective folding of
some essential proteins. Co-expression of Hsp60-(p.V98I) and wild-type Hsp60
exerted a dominant negative effect only when the chaperonin genes were
expressed at relatively low levels. Based on our in vivo and in
vitro data, we propose that the major effect of heterozygosity for the
Hsp60-(p.V98I) mutation is a moderately decreased activity of chaperonin
complexes composed of mixed wild-type and Hsp60-(p.V98I) mutant subunits