ALPHA-TUBULIN ACETYLATION AS CRUCIAL REGULATOR OF CYTOSKELETAL FUNCTIONS IN MOTOR NEURONS

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disorder marked by selective loss of motor neurons, ultimately resulting in paralysis and respiratory failure. Due to their elongated axons, motor neurons rely heavily on cytoskeletal functions to maintain cargo transport from the soma to the neuromuscular junction. Indeed, early axonal transport and neurite outgrowth defects are a common hallmark in models for familial and sporadic ALS. Interestingly, inhibition of histone deacetylase 6 (HDAC6) has been shown to alleviate these defects but the underlying molecular mechanism remains unknown. However, one of its substrates is the deacetylation of alpha-tubulin, previously suggested to be implicated in cytoskeletal functions. To gain molecular substrates into the modulation of this therapeutic substrate, we assessed the impact of modulated alpha-tubulin acetylation levels using commercial compounds on different cytoskeletal functions in healthy iPSC-derived motor neurons. Interestingly, increased alpha-tubulin acetylation through HDAC6 inhibition had no impact on axonal transport or neurite outgrowth in healthy motor neurons. In contrast, reduced alpha-tubulin acetylation through inhibition of aTAT1 resulted in dose-dependent axonal transport defects and neurite collapsing, highlighting the importance of this modification in cytoskeletal functions specifically. In conclusion, our findings show that while increased alpha-tubulin acetylation via HDAC6 inhibition does not influence cytoskeletal functions in healthy motor neurons, a reduction in alpha-tubulin acetylation via aTAT1 inhibition, leads to axonal transport defects and neurite collapse, emphasizing the critical role of alpha-tubulin acetylation in maintaining cytoskeletal functions and highlighting the potential therapeutic implications of targeting this pathway in ALS.