HTT and Huntington disease: HD leads to impairment in proteasome activity as a consequence of the expression of polyglutamine-expanded huntingtin, compromises neuronal homeostasis by decreasing the transcription of essential genes in neurotransmission and signaling and enhances the JNK3 phosphorylation of kinesin heavy chain, which disrupts its binding to microtubules leading to impaired and slow axonal transport.