Choe, Y.-J. | bioRxiv Science

bioRxiv2024

FDA approved PDE4 inhibitors reduce the dominant toxicity of ALS/FTD associated CHCHD10S59L

Mutations in coiled-coil-helix-coiled-coil-helix domain containing 10(CHCHD10) have been identified as a genetic cause of amyotrophic lateral sclerosis and/or frontotemporal dementia(ALS-FTD). In our previous studies using in vivo Drosophila model expressing C2C10HS81L, and human cell models expressing CHCHD10S59L, we have identified that the PINK1/Parkin pathway is activated and causes cellular toxicity. Furthermore, we demonstrated that pseudo-substrate inhibitors for PINK1 and mitofusin2 agonists mitigated the cellular toxicity of CHCHD10S59L. Evidences using in vitro/ in vivo genetic and chemical tools indicate that inhibiting PINK1 would be the most promising treatment for CHCHD10S59L-induced diseases. Therefore, we have investigated cellular pathways that can modulate the PINK1/Parkin pathway and reduce CHCHD10S59L-induced cytotoxicity. Here, we report that FDA-approved PDE4 inhibitors reduced CHCHD10S59L-induced morphological and functional mitochondrial defects in human cells and an in vivo Drosophila model expressing C2C10HS81L. Multiple PDE4 inhibitors decreased PINK1 accumulation and downstream mitophagy induced by CHCHD10S59L. These findings suggest that PDE4 inhibitors currently available in the market may be repositioned to treat CHCHD10S59L-induced ALS-FTD and possibly other related diseases.

neuroscience↗

bioRxiv2023

The 21-base pair deletion mutant Calpain 3 does not inhibit wild-type Calpain 3 activity

IntroductionCalpain 3 is one of the calpain protease family members, which is a calcium-dependent proteolytic enzyme predominantly expressed in skeletal muscle. Loss-of-function mutations in the Calpain 3 gene have been related to autosomal recessive Limb-Girdle Muscular Dystrophy 1 (LGMDR1), a common form of muscular dystrophy. Recently, the heterozygous 21-bp deletion mutation of the Calpain 3 gene has been reported to cause autosomal dominant Limb-Girdle Muscular Dystrophy 4 (LGMDD4). According to its dominant inheritance pattern, it has been suggested that the deletion mutant proteins act in a dominant-negative manner. Therefore, we examined whether the mutant protein can suppress the activity of wild-type Calpain 3 and has any dominant toxicity in cell culture and in vivo Drosophila models. MethodsA human cell culture (HeLa cells) model with the transient transfection of human wild-type and mutant Calpain 3 and in vivo Drosophila models overexpressing wild-type and mutant Drosophila Calpain A and B were utilized in this study to assess dominant effects of Calpain 3 21-bp deletion mutant. Western blot analysis was used to determine protein stability and catalytic activity in cell culture. External eye morphology and muscle integrity were examined to observe dominant toxicity in Drosophila models. ResultsThe 21-bp deletion mutation of Calpain 3 resulted in catalytic inactivation, which did not inhibit wild-type Calpain 3 autolytic and catalytic activity against Calpastatin in HeLa cells. In addition, the mutant protein was normally processed by wild-type Calpain 3. Overexpression of wild-type and deletion mutant Calpain 3 in the Drosophila eye and muscles did not exhibit significant developmental and age-related dominant toxicity. DiscussionWe provide evidence that mutant Calpain 3 does not suppress wild-type Calpain 3 activity. Rather, it is a mutant lacking autocatalytic processing activity like many other loss-of-function Calpain 3 mutants causing LGMDR1. Our results implicate that the stability of the heteromeric mutant and wild-type Calpain 3 complexes may be affected without inhibiting the wild-type activity per se. However, a more thorough investigation is necessary to understand the molecular mechanism and dominant inheritance of the heterozygous 21-bp deletion mutation in LGMDD4.

cell biology↗