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bioRxiv · 10.64898/2026.07.30.741783

TRIM9 Determines Sex-Specific β-Amyloid/Cellular Prion Protein/mGluR5 Complex Formation and Pathological Signaling in Alzheimer's Disease Mice

Babaei, F.·Arasi, F. P.·Colson, T.-L. L.·Cheng, H.·Tiberi, M.·Chidiac, R.·Angers, S.·Gupton, S. L.·Abd-Elrahman, K. S.·Ferguson, S. S. G.
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Abstract

Biological sex is a major determinant of Alzheimers disease prevalence, yet the molecular mechanisms underlying sex-specific vulnerability remain largely unknown. Metabotropic glutamate receptor 5 (mGluR5) functions as a co-receptor for {beta}-amyloid (A{beta}42) oligomer/cellular prion protein (PrPC)-mediated pathogenic signaling in males but not females, establishing a sex-dimorphic node in {beta}-amyloid pathophysiology whose regulatory basis is undefined. Using quantitative proteomic analysis, we identify the E3 ubiquitin ligase TRIM9 as a novel mGluR5-interacting protein and a previously unrecognized sex-specific regulator of the A{beta}42/PrPC/mGluR5 complex. TRIM9 selectively associates with mGluR5 in male but not female APP/PS1 mouse brain and is required for mGluR5 to serve as a co-receptor for PrPC-dependent A{beta}42 oligomer binding. Genetic deletion of TRIM9 abolishes A{beta}42/PrPC/mGluR5 complex assembly in male APP/PS1 mice demonstrating that TRIM9 is an essential scaffold for male-specific A{beta}42 signal transduction. Loss of TRIM9 in males further reduces {beta}-amyloid pathology by restoring Akt/GSK3{beta}/ZBTB16-dependent autophagic flux, linking disruption of this complex to a defined downstream proteostatic mechanism. Together, these findings establish TRIM9 as a critical molecular determinant coupling male-specific A{beta}42/PrPC/mGluR5 complex assembly to downstream neurodegenerative signaling and {beta}-amyloid pathology. They reveal an unappreciated layer of sex-dependent complexity in mGluR5 pharmacology and identify disruption of the TRIM9/mGluR5 interaction as a potential male-specific therapeutic strategy for Alzheimers disease. Significance StatementThe molecular basis of sex differences in Alzheimers disease vulnerability remains unresolved. We show that mGluR5 functions as a male-specific co-receptor for pathogenic A{beta}42/PrPC signaling and identify the E3 ubiquitin ligase TRIM9 as the factor governing this dimorphism. TRIM9 selectively assembles the A{beta}42/PrPC/mGluR5 complex in male brain, and its genetic deletion disrupts complex formation while restoring Akt/GSK3{beta}-dependent autophagic clearance of amyloid. These findings define a sex-specific signaling axis underlying {beta}-amyloid pathogenesis and establish TRIM9 as a candidate target for sex-informed Alzheimers therapeutics.

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Babaei, F., Arasi, F. P., Colson, T.-L. L., Cheng, H., Tiberi, M., Chidiac, R., Angers, S., Gupton, S. L., Abd-Elrahman, K. S., Ferguson, S. S. G.. 2026-08-04. TRIM9 Determines Sex-Specific β-Amyloid/Cellular Prion Protein/mGluR5 Complex Formation and Pathological Signaling in Alzheimer's Disease Mice. https://doi.org/10.64898/2026.07.30.741783

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