In neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD), the persistent accumulation of misfolded proteins, such as amyloid-β (Aβ), α-synuclein (αSyn), and mutant huntingtin (mHtt), overwhelms the folding capacity of the endoplasmic reticulum (ER), triggering a protective signaling network known as the unfolded protein response (UPR) [18]. This evidence concerns the gene HTT and Parkinson disease.