Neuronal cell line expressing full-length mutant huntingtin displays alteration of proteasome activity

Polyglutamine diseases are incurable genetic neurodegenerative disorders characterized by the accumulation of extended polyglutamine fragments-containing mutant proteins, which are prone to the formation of poorly soluble aggregates. The adequate cellular model is crucial in uncovering the pathological mechanisms responsible for neurotoxicity in HD, screening for therapeutic molecules and elucidation of the molecular mechanisms impacted by particular compound. In the present study, genetic constructs based on the Sleeping Beauty system were created for the stable inducible expression of full-length normal and mutant huntingtin (Htt) in eukaryotic cells. These constructs were then employed to develop model neuronal cells using Neuro-2a cell line. The expression of Htt as well as the accumulation of Htt immunopositive intracellular aggregates (most characteristic features of HD) was demonstrated, and these aggregates showed colocalization with the proteasome. The activation of the proteasome, as well as changes in the expression of proteasome regulators, components of the autophagy system, and the neuronal proteases cathepsins B and D, reflect the versatility of cellular responses to the mutant pathological forms of Htt.