Neurodegenerative pathways (Parkinson’s, prion diseases) and proteasomal dysfunction link to mitochondrial stress and neurotrophin signaling, while viral infections (HIV-1, HSV-1, HCMV) exploit host ribosomes and lysosomes, underscoring complex host–pathogen interactions in disease pathogenesis (Figure 4B). The gene discussed is BDNF; the disease is viral infectious disease.