HAP/ClpP-mediated disaggregation and degradation of Mutant SOD1 aggregates: A potential therapeutic strategy for Amyotrophic lateral sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease marked by the accumulation of misfolded Cu/Zn superoxide dismutase (SOD1) protein aggregates in motor neurons, leading to progressive motor dysfunction and ultimately death. While the molecular chaperone heat shock protein 104 (Hsp104) has been shown to reduce protein misfolding by disaggregating protein aggregates, fully degrading these disaggregated proteins remains a significant challenge. In this study, we have investigated the effects of Hsp104 and its hyperactive variant, HAP, in combination with caseinolytic protease P (CIpP), on the disaggregation and degradation of SOD1 aggregates. Using laser confocal microscopy, fluorescence loss in photobleaching (FLIP), and biomolecular fluorescence complementation (BiFC)-fluorescence resonance energy transfer (FRET) assays, we demonstrate that Hsp104 effectively disaggregates SOD1 aggregates across 14 different G93 mutants, classified based on the properties of substituted amino acids, thus restoring protein mobility. Notably, the HAP/CIpP system not only disaggregates ALS-associated SOD1^G93A aggregates but also promotes their proteolytic degradation, as evidenced by a significant reduction in high-order oligomers observed through BiFC and FRET assays. This dual mechanism of action presents. the HAP/CIpP system holds significant therapeutic potential for ALS and other neurodegenerative diseases characterized by protein aggregates, as it enables both effective disaggregation and degradation of toxic protein aggregates, thereby maintaining protein homeostasis.