Mission cholesterol: Uncovering its hidden role in ALS neurodegeneration.

Cholesterol is a central determinant of membrane architecture, signaling, and cellular homeostasis in the central nervous system (CNS). While historically viewed as a structural component, emerging evidence highlights its dynamic regulatory role in neuronal function, particularly through its compartmentalized synthesis, trafficking, and turnover. This review examines the complex landscape of cholesterol metabolism in the CNS, emphasizing the cooperative roles of astrocytes and neurons, the partitioning of biosynthetic pathways, and the barriers that distinguish brain cholesterol pools from peripheral sources. We focus on mitochondria-associated endoplasmic reticulum membranes (MAMs) as key regulatory platforms for cholesterol sensing, esterification, and signaling, underscoring their emerging role in neurodegenerative diseases. Disruptions in MAM integrity, lipid raft composition, and transcriptional regulation of cholesterol-handling genes have been linked to pathologies such as amyotrophic lateral sclerosis (ALS), particularly through the actions of TDP-43. By consolidating recent findings from lipidomics, cell biology, and disease models, we propose that cholesterol dyshomeostasis constitutes a shared mechanistic axis across diverse neurodegenerative conditions. Understanding this axis offers novel insights into the metabolic vulnerability of neurons and highlights cholesterol metabolism as a promising target for therapeutic intervention.