TREM2-complement-amyloid axis as therapeutic target for protein aggregation disorders

The TREM2-complement-amyloid signaling axis identified in Alzheimer's disease (where TREM2 activation on microglia promotes amyloid clearance via complement-mediated synaptic pruning regulation) shares structural homology with the protein aggregation pathology in the target unknown disease. Specifically, TREM2-mediated complement activation represents a conserved microglial mechanism for regulating protein aggregate clearance that may be transferable. In AD, loss-of-function TREM2 variants impair this clearance pathway; we predict that enhancing TREM2 signaling in the unknown disease context will similarly enhance protein aggregate clearance via complement-dependent mechanisms.

The TREM2-complement-amyloid signaling axis identified in Alzheimer's disease (where TREM2 activation on microglia promotes amyloid clearance via complement-mediated synaptic pruning regulation) shares structural homology with the protein aggregation pathology in the target unknown disease. Specifically, TREM2-mediated complement activation represents a conserved microglial mechanism for regulating protein aggregate clearance that may be transferable. In AD, loss-of-function TREM2 variants impair this clearance pathway; we predict that enhancing TREM2 signaling in the unknown disease context will similarly enhance protein aggregate clearance via complement-dependent mechanisms. This predicts a measurable increase in aggregate clearance rate and restoration of complement homeostasis when TREM2 is pharmacologically enhanced or genetically overexpressed.

Analogy rationale: The TREM2-complement-protein aggregate mechanism represents a conserved microglial pathway: TREM2 senses lipid changes associated with protein aggregates, activates complement to target aggregates for phagocytosis, and promotes clearance. This molecular logic (sensor → complement amplifier → effector clearance) transfers because the underlying biochemistry of TREM2 lipid binding and complement recruitment is disease-independent.

Disanalogies: Critical disanalogies include: (1) Different aggregate proteins (Aβ42 vs. α-synuclein/tau/TDP-43) have distinct proteostasis vulnerabilities; (2) TREM2 polymorphisms show differential effect sizes across diseases; (3) Microglial cell states and regional distributions vary significantly; (4) The blood-brain barrier integrity and age-related changes differ; (5) Non-amyloid diseases may lack the specific lipid signatures (gangliosides, cholesterol) that optimize TREM2 binding to Aβ.

Falsifiable prediction: If TREM2 enhances amyloid clearance in the target disease via complement, then in a mouse model of the target disease (e.g., transgenic line with disease-relevant protein aggregate expression), TREM2 overexpression or TREM2-agonist treatment will produce a ≥30% reduction in SDS-insoluble aggregate load (measured by ELISA or filter trap assay) and increased complement C1q/C3 deposition on aggregates at 3 months post-treatment, compared to vehicle controls. Failure to observe aggregate reduction would falsify the analogy.
This hypothesis was generated from `h-var-e95d2d1d86` in `Alzheimer's disease` — judge it on its own merits but acknowledge the source.