The Pivotal Role of HDAC6 in Amyotrophic Lateral Sclerosis: Neuroprotective Protagonist or Degenerative Adversary?

The review specifically examines the pivotal role of HDAC6 in the pathophysiological pathway of Amyotrophic Lateral Sclerosis (ALS), an escalating neurodegenerative ailment marked by the discerning damage to motor neurons. Several lines of evidence implicate inadequate proteostasis in significantly influencing neuronal degeneration. The accumulation of misfolded proteins and proteotoxicity are highlighted as significant factors in ALS pathophysiology. Key pathological hallmarks include ubiquitin-positive inclusions, disrupted RNA metabolism, cytoskeletal perturbations, and compromised axonal transport systems. HDAC6 dysregulation disrupts axonal transport, impairing mitochondrial function and increasing oxidative stress, leading to rapid motor neuron damage and cell death. The enzyme's aberrant deacetylation of α-tubulin destabilizes microtubules and impairs intracellular trafficking. Despite HDAC6's participation in these unfavorable processes, it also exerts neuroprotective properties. It deacetylates tubulin, promoting efficient axonal transport and autophagic clearance. HDAC6 helps form aggresomes and stress granules, which are essential for cellular defence against proteotoxic stress. Through its zinc finger ubiquitin-binding domain, HDAC6 interacts with polyubiquitinated proteins, facilitating their autophagic degradation. HDAC6 inhibition can boost autophagic flux and reduce protein aggregation, while its activation may amplify the protective effects. This dichotomous behaviour of HDAC6 may pose an obstacle to the design of targeted therapy. Illuminating the complex mechanisms through which HDAC6 influences neurodegeneration and neuroprotection is important before constructing effective treatments for ALS. The review provides a clear understanding of the complex role of HDAC6 in ALS pathogenesis and highlights potential strategies to improve the prognosis of people affected by this neurological illness.