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Personalized Treatment for Infantile Ascending Hereditary Spastic Paralysis Based on In Silico Strategies
Matteo Rossi Sebastiano1, Giuseppe Ermondi1, Kai Sato2
1Molecular Biotechnology and Health Sciences Department, University of Torino, Quarello 15, 10135 Torino, Italy.
Insights
Infantile onset hereditary spastic paralysis (IAHSP) is a rare neurological disorder caused by ALS2 gene mutations. A new drug candidate, MK4, was identified to restore alsin tetramer formation, offering potential treatment for patients with specific ALS2 mutations.
Area of Science:
- Neuroscience
- Genetics
- Drug Discovery
Background:
- Infantile onset hereditary spastic paralysis (IAHSP) is a rare, recessively inherited neurodevelopmental disorder.
- Mutations in the *ALS2* gene, encoding the protein alsin, cause IAHSP by affecting upper motoneuron development.
- Alsin functions as an active tetramer, with dimerization mediated by its C-terminal VPS9 domain.
Purpose of the Study:
- To investigate the pathogenic mechanisms of *ALS2* mutations in IAHSP.
- To identify a therapeutic strategy for IAHSP by targeting alsin's abnormal dimerization.
- To discover a drug candidate capable of restoring functional alsin tetramers.
Main Methods:
- Protein modeling to analyze the R1611W mutation's impact on VPS9 domain stability and flexibility.
- In vitro assays to assess alsin homo-dimerization and tetramer formation.
- Virtual screening to identify compounds that can rescue the mutant alsin phenotype.
- Cellular assays in HeLa cells to validate the drug candidate's efficacy.
Main Results:
- The R1611W mutation disrupts alsin homo-dimerization, preventing the formation of active tetramers.
- Virtual screening identified MK4, a known therapeutic compound, as a potential masker of the R1611W mutation.
- MK4 successfully re-established alsin tetramer formation in HeLa cells harboring the R1611W mutation.
Conclusions:
- The R1611W mutation in the *ALS2* gene impairs alsin function through abnormal dimerization.
- MK4 demonstrates potential as a therapeutic agent for IAHSP by restoring alsin tetramer assembly.
- This study highlights an innovative drug discovery approach for rare neurodevelopmental diseases.
Abstract:
Infantile onset hereditary spastic paralysis (IAHSP) is a rare neurological disease diagnosed in less than 50 children worldwide. It is transmitted with a recessive pattern and originates from mutations of the ALS2 gene, encoding for the protein alsin and involved in differentiation and maintenance of the upper motoneuron. The exact pathogenic mechanisms of IAHSP and other neurodevelopmental diseases are still largely unknown. However, previous studies revealed that, in the cytosolic compartment, alsin is present as an active tetramer, first assembled from dimer pairs. The C-terminal VPS9 domain is a key interaction site for alsin dimerization. Here, we present an innovative drug discovery strategy, which identified a drug candidate to potentially treat a patient harboring two ALS2 mutations: one truncation at lysine 1457 (not considered) and the substitution of arginine 1611 with a tryptophan (R1611W) in the C-terminus VPS9. With a protein modeling approach, we obtained a R1611W mutant model and characterized the impact of the mutation on the stability and flexibility of VPS9. Furthermore, we showed how arginine 1611 is essential for alsin's homo-dimerization and how, when mutated to tryptophan, it leads to an abnormal dimerization pattern, disrupting the formation of active tetramers. Finally, we performed a virtual screening, individuating an already therapy-approved compound (MK4) able to mask the mutant residue and re-establishing the alsin tetramers in HeLa cells. MK4 has now been approved for compassionate use.
