Mapping the chaperonin TRiC/CCT interactome in mouse photoreceptors reveals functional significance for energy metabolism

Brooks, C.; Salcedo Tacuma, D.; Mascari, I.; Eminhizer, M.; Ngo, T.; Kolson, D.; Sechrest, E.; Guan, T.; Billington, N.; Deng, W. T.; Smith, D.; Du, J.; Skiba, N.; Sokolov, M.

doi:10.64898/2026.03.12.711399

bioRxiv · 10.64898/2026.03.12.711399

Mapping the chaperonin TRiC/CCT interactome in mouse photoreceptors reveals functional significance for energy metabolism

Brooks, C.·Salcedo Tacuma, D.·Mascari, I.·Eminhizer, M.·Ngo, T.·Kolson, D.·Sechrest, E.·Guan, T.·Billington, N.·Deng, W. T.·Smith, D.·Du, J.·Skiba, N.·Sokolov, M.

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Abstract

The eukaryotic chaperonin TRiC/CCT is essential for folding a diverse set of proteins, yet its interactome and functional roles in specialized neurons remain incompletely understood. To investigate TRiC-mediated folding in rod photoreceptors, we generated a transgenic mouse line expressing an epitope-tagged Tcp-1 subunit, enabling purification of intact TRiC complexes from retinal tissue. Mass spectrometry identified 226 TRiC-interacting proteins, including known TRiC substrates and co-chaperones as well as numerous novel candidates enriched in RNA processing, cytoskeletal organization, and cell-cycle regulation. Using a TRiC loss-of-function model in which expression of a short splice isoform of phosducin-like protein (PhLPs) competitively inhibits TRiC activity, we observed marked reductions in canonical TRiC substrates, including tubulins, transducin {beta} subunits, and triosephosphate isomerase, as well as secondary alterations in proteins involved in cytoskeletal stability, membrane trafficking, energy metabolism, and phototransduction. Quantitative metabolomic profiling revealed that TRiC deficiency induces a metabolic "energy crisis" characterized by reduced glycolytic- and tricarboxylic acid cycle intermediates, acylcarnitines, ATP, NAD, and NADH, implicating widespread impairment of glucose utilization, mitochondrial bioenergetics, and fatty acid oxidation. Integrative proteomic-metabolomic analysis identified a small subset of proteins, including Rab10 and Anxa1, as potential drivers of these metabolic disruptions, with defective Rab10-dependent GLUT4 trafficking emerging as a plausible mechanism underlying impaired glucose uptake in TRiC-deficient rods. Finally, experiments using a perpetually unfolded G{beta}1 mutant and G{gamma}1-knockout mice demonstrated that substrate overload sequesters TRiC and competitively displaces other clients, exacerbating proteostasis imbalance. Together, our study provides a comprehensive in vivo mapping of the TRiC interactome in mammalian rods, reveals a connection between TRiC-dependent proteostasis and energy metabolism in rods, and indicates a mechanism by which misfolded TRiC substrates exacerbate a proteostasis imbalance that ultimately results in neurodegeneration.

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Brooks, C., Salcedo Tacuma, D., Mascari, I., Eminhizer, M., Ngo, T., Kolson, D., Sechrest, E., Guan, T., Billington, N., Deng, W. T., Smith, D., Du, J., Skiba, N., Sokolov, M.. 2026-03-15. Mapping the chaperonin TRiC/CCT interactome in mouse photoreceptors reveals functional significance for energy metabolism. https://doi.org/10.64898/2026.03.12.711399

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