Protein misfolding and its dual role in neurodegeneration and cancer progression

Protein misfolding is a fundamental biological process with profound implications for human health and disease. Typically, proteins assume precise three-dimensional structures to perform their functions, a process safeguarded by the proteostasis network, which comprises molecular chaperones, the ubiquitin-proteasome system (UPS), and autophagy. However, genetic mutations, oxidative stress, and environmental insults can disrupt folding, leading to the accumulation of non-functional or toxic conformations. In neurodegenerative diseases such as Huntington's disease (HD), Parkinson's disease (PD), Alzheimer's disease (AD), Amyotrophic lateral Sclerosis (ALS), chronic misfolding results in toxic protein aggregates like amyloid-β, tau, and α-synuclein. These disrupt synaptic function, induce oxidative and nitrosative stress, and trigger apoptosis, ultimately leading to progressive neuronal loss. Dysregulation of the unfolded protein response (UPR) and weakened proteostasis with aging exacerbate disease pathology. In contrast, cancer cells utilize protein misfolding to enhance their survival and progression. Misfolded oncoproteins, such as mutant p53, not only evade degradation but also acquire oncogenic properties. Tumor cells hijack the UPR and chaperone networks, upregulate heat shock proteins, and manipulate oxidative stress responses to withstand hypoxia, nutrient deprivation, and rapid proliferation. Cancer stem cells (CSCs) further adapt to proteotoxic stress, contributing to tumor heterogeneity, therapy resistance, and immune evasion. The dual role of protein misfolding, driving degeneration in neurons while supporting proliferation in tumors, underscores its centrality in disease biology. Future research should focus on identifying early biomarkers of proteostasis imbalance and exploiting shared molecular pathways for the development of novel therapeutic interventions.