Overview
The regulatory mechanisms governing de novo purine biosynthesis remain poorly understood. Recent work has revealed that two enzymes in this pathway, FGAMS and PPAT, are clients of the molecular chaperone HSP90 and associate with its co-chaperone, HSP70. These findings point to a direct role for the cellular protein-folding machinery in controlling metabolic enzyme stability, activity, and spatial organization.
Disruption of chaperone function leads to decreased enzyme stability and enhanced degradation. Notably, loss of functional FGAMS perturbs the liquid-like properties of the purinosome, driving a transition toward assemblies that resemble insoluble aggregates, suggesting that chaperone-mediated folding is essential for maintaining both enzyme function and condensate integrity.
Research Strategy
We hypothesize that HSP70 stabilizes immature purine biosynthetic enzymes and facilitates their transfer to HSP90, where they undergo productive folding into catalytically active states. Inhibition of HSP90 disrupts these interactions, resulting in enzyme destabilization and impaired purinosome function.
Proteome-wide analyses of the HSP90 interactome suggest that specific co-chaperones and accessory proteins direct folding of distinct classes of clients, such as kinases and E3 ubiquitin ligases. In this project, we ask whether analogous, specialized chaperone networks exist for metabolic enzymes. Using a combination of protein proximity labeling, biochemical approaches, and cryo-electron microscopy, we aim to define how chaperone complexes recognize, fold, and regulate purine biosynthetic enzymes, and how this regulation shapes metabolic flux through the purinosome.
Outstanding Questions
- How do molecular chaperones regulate folding and stability of purine biosynthetic enzymes?
- Are specific co-chaperones required for recruitment and maturation of metabolic enzymes?
- How does chaperone-mediated folding influence purinosome material properties?
- Can disruption of chaperone–enzyme interactions alter metabolic flux in disease-relevant contexts?
Publications
- Binder, M.J. and Pedley, A.M., The Roles of Molecular Chaperones in Regulating Cell Metabolism. FEBS Lett 2023, 597(13), 1681-1701.
- Pedley, A. M.; Boylan, J. P.; Chan, C. Y.; Kennedy, E. L.; Kyoung, M.; Benkovic, S. J., Purine biosynthetic enzymes assemble into liquid-like condensates dependent on the activity of chaperone protein HSP90. J Biol Chem 2022, 298(5), 101845.
- Liu, C.*; Knudsen, G. M.*; Pedley, A. M.*; He, J.; Johnson, J. L.; Yaron, T. M.; Cantley, L. C.; Benkovic, S. J., Mapping Post-Translational Modifications of de Novo Purine Biosynthetic Enzymes: Implications for Pathway Regulation. J Proteome Res 2019, 18(5), 2078-2087.
- Pedley, A. M.; Karras, G. I.; Zhang, X.; Lindquist, S.; Benkovic, S. J., Role of HSP90 in the Regulation of de Novo Purine Biosynthesis. Biochemistry 2018, 57(23), 3217-3221.