Posted - December 2019 in Research Highlights
Same gene & mechanism causes another disorder
Diminished ability in folding mitochondrial proteins results in impaired aerobic respiration in the hsp60 (heat shock protein) gene.
This mechanism is proposed as the cause of SPG13 as well as a mitochondrial disorder.
The human mitochondrial heat shock protein 60 (hsp60) is a tetradecameric chaperonin that folds proteins in the mitochondrial matrix. An hsp60 D3G mutation leads to MitCHAP-60, an early onset neurodegenerative disease while hsp60 V72I has been linked to SPG13, a form of hereditary spastic paraplegia.
Previous studies have suggested that these mutations impair the protein folding activity of hsp60 complexes but the detailed mechanism by which these mutations lead to the neuromuscular diseases remains unknown. It is known, is that the β-subunit of the human mitochondrial ATP synthase co-immunoprecipitates with hsp60 indicating that the β-subunit is likely a substrate for the chaperonin. Therefore, we hypothesized that hsp60 mutations cause misfolding of proteins that are critical for aerobic respiration.
Negative-stain electron microscopy and DLS results suggest that the D3G and V72I complexes fall apart when treated with ATP or ADP and are therefore unable to fold denatured substrates such as α-lactalbumin, malate dehydrogenase (MDH), and the β-subunit of ATP synthase in in-vitro protein-folding assays. These data suggests that hsp60 plays a crucial role in folding important players in aerobic respiration such as the β-subunit of the ATP synthase. The hsp60 mutations D3G and V72I impair its ability to fold mitochondrial substrates leading to abnormal ATP synthesis and the development of the MitCHAP-60 and SPG13 neuromuscular degenerative disorders.
SOURCE: Sci Rep. 2019 Aug 23;9(1):12300. doi: 10.1038/s41598-019-48762-5. PMID: 31444388
MitCHAP-60 and Hereditary Spastic Paraplegia SPG-13 Arise from an Inactive hsp60 Chaperonin that Fails to Fold the ATP Synthase β-Subunit.
1 University of Texas at El Paso, Department of Chemistry and Biochemistry, 500 West University Ave., El Paso, Texas, 79968, USA.
2 University of Texas at El Paso, Department of Chemistry and Biochemistry, 500 West University Ave., El Paso, Texas, 79968, USA.
3 University of Texas at El Paso, Department of Chemistry and Biochemistry, 500 West University Ave., El Paso, Texas, 79968, USA.