Isoform-selective HSP90 inhibition as a precision therapeutic strategy for neurodegenerative and metabolic diseases.

Heat shock protein 90 (HSP90) is a central regulator of cellular proteostasis, coordinating the folding, stabilization, and turnover of a wide range of client proteins in the cytosol, endoplasmic reticulum, and mitochondria. Accumulating evidence indicates that the four HSP90 paralogs HSP90α, HSP90β, GRP94, and TRAP1 have distinct pathological roles in neurodegenerative and metabolic diseases. In neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis, aberrant HSP90 activity contributes to the persistence of toxic protein conformers, defective autophagy, mitochondrial dysfunction, and chronic neuroinflammation. In metabolic disorders such as obesity, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease, GRP94- and TRAP1-dependent signaling promotes endoplasmic reticulum stress, impaired mitochondrial metabolism, insulin resistance, and inflammatory remodeling. These mechanistic insights have accelerated the development of a new generation of HSP90 inhibitors with improved selectivity, tissue targeting, and brain penetration. Unlike earlier pan-HSP90 inhibitors, these compounds are designed to exploit paralog-specific vulnerabilities and may enable safer long-term modulation of disease-relevant chaperone networks. This review summarizes current advances in the biology and pharmacology of HSP90 paralogs and proposes isoform-selective HSP90 targeting as a promising therapeutic strategy at the intersection of neurodegeneration and metabolic dysfunction.