HTT and juvenile Huntington disease: I. Curli exhibits cross-seeding and colocalization with α-syn in both C. elegans neurons and human neuroblastoma cells.II. Curli-induced α-syn aggregations inhibit mitochondrial gene expression, leading to energy failure in neurons.III. Curli may promote neuropathologies caused by many aggregation-prone proteins, including Aβ in Alzheimer’s disease, Huntingtin in Huntington’s disease, and SOD1 in amyotrophic lateral sclerosis.