Broken Balance: Emerging Cross-Talk Between Proteostasis and Lipostasis in Neurodegenerative Diseases.

Neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease, are characterized by progressive neuronal loss, leading to cognitive and motor impairments. Although these diseases have distinct clinical manifestations, they share pathological hallmarks such as protein aggregation and lysosomal dysfunction. The lysosome plays a vital role in maintaining cellular homeostasis by mediating the degradation and recycling of proteins, lipids, and other macromolecules. As such, it serves as a central hub for both proteostasis and lipostasis. This review outlines genetic and mechanistic parallels between rare lysosomal lipid storage diseases, such as Gaucher disease and Niemann-Pick disease, and more prevalent neurodegenerative diseases. We discuss how impaired lysosomal sphingolipid metabolism compromises lysosomal integrity, disrupts proteostasis, and contributes to neurodegeneration. Furthermore, we describe how age-related decline in lysosomal function may similarly drive neurodegeneration in the absence of overt genetic mutations. Taken together, this review highlights the lysosome as a central integrator of protein and lipid homeostasis and emphasizes the bidirectional relationship between lipostasis and proteostasis, whereby disruption of one adversely affects the other in the pathogenesis of multiple neurodegenerative diseases.