Disrupting proteasomal and autophagic degradation systems of misfolded
alpha-sarcoglycan protein by bortezomib and givinostat combination
Abstract
Background and Purpose: Limb-girdle muscular dystrophy type R3 (LGMD R3)
is a rare genetic disorder characterized by a progressive proximal
muscle weakness and caused by mutations in the SGCA gene encoding
alpha-sarcoglycan (α-SG). Here, we report the results of a mechanistic
screening ascertaining the molecular mechanisms involved in the
degradation of the most prevalent misfolded R77C-α-SG protein.
Experimental Approach: We performed a combinatorial study to identify
drugs potentializing the effect of a low dose of the proteasome
inhibitor bortezomib on the R77C-α-SG degradation inhibition. Key
Results: Analysis of the screening associated to artificial
intelligence-based predictive ADMET characterization of the hits led to
identification of the HDAC inhibitor givinostat as potential
therapeutical candidate. Functional characterization revealed that
givinostat effect was related to autophagic pathway inhibition,
unveiling new theories concerning degradation pathways of misfolded SG
proteins. Conclusion and Implications: Beyond the identification of a
new therapeutic option for LGMD R3 patients, our results shed light on
the potential repurposing of givinostat for the treatment of other
genetic diseases sharing similar protein degradation defects such as
LGMD R5 and cystic fibrosis.