Triggering receptor expressed on myeloid cells 2

Overview

Triggering receptor expressed on myeloid cells 2 (TREM2) is a myeloid-cell surface receptor encoded by the TREM2 gene. It is expressed prominently in cells of the innate immune system, including microglia and macrophage populations, where it participates in sensing tissue damage, regulating inflammatory responses, and supporting cell survival and differentiation. In biomedical research, TREM2 is widely studied as a disease-associated immune regulator rather than as a classical enzyme or structural protein target.

TREM2 has attracted substantial attention in neurodegeneration, especially Alzheimer’s disease, where genetic variants are associated with increased risk and altered microglial function. It is also increasingly implicated in metabolic and fibrotic disease states, including Metabolic dysfunction associated steatohepatitis and liver fibrosis, where TREM2-expressing macrophage subsets appear to contribute to disease-associated immune remodeling. Because of these roles, TREM2 is being explored both as a mechanistic biomarker and as a therapeutic target.

Recent Publications Focus

• Elamipretide (SS-31) and nicotinamide mononucleotide (NMN) combination therapy in post-ischemic brain injury: A 2026 study reported that this combination was evaluated for its ability to mitigate post-ischemic brain injury in mice, with a specific focus on modulation of TREM2-mediated neuroinflammatory and apoptotic pathways 42443448Jul. This places TREM2 within a broader neuroprotective framework involving mitochondrial support and injury-response signaling.

• Labile iron starvation in embryonic Kupffer cells and MASH: A 2026 Cell Death & Disease study found that Fe2+ deficiency blunts TREM2 expression, whereas restoring Fe2+ homeostasis elevates embryonic Kupffer cell TREM2 abundance in Metabolic dysfunction associated steatohepatitis (MASH) liver 42310295Jun. The findings connect iron availability to TREM2-linked macrophage function and suggest that impaired TREM2 expression may contribute to macrophage dysfunction and mitochondrial failure in the diseased liver.

• H4K12 lactylation and TREM2high macrophage differentiation in liver fibrosis: A 2026 Hepatology study reported that TREM2-expressing scar-associated macrophages are integral to the pathogenesis of hepatic fibrosis 42307631Jun. The work specifically focused on H4K12 lactylation as a driver of TREM2high macrophage differentiation, highlighting an epigenetic mechanism that promotes a fibrogenic macrophage state.

• Mechanisms of increased Alzheimer’s disease pathology with R47H and R62H TREM2 variants: A 2026 Acta Neuropathologica study examined how the R47H and R62H TREM2 variants influence Alzheimer’s disease pathology 42298074Jun. The publication emphasized that TREM2 plays multiple functional roles in microglia and that variants in this gene are associated with increased risk of Alzheimer’s disease, reinforcing its importance in microglial biology and disease susceptibility.

• Gene editing technologies and TREM2 in Alzheimer’s disease: A 2026 review in Current Aging Science discussed the potential of gene editing to target genetic risk factors associated with Alzheimer’s disease, including APOE4 and TREM2, and to improve the differentiation and functionality of induced pluripotent stem cells derived from Alzheimer’s disease patients 41926312Apr. In this context, TREM2 is presented as both a genetic risk factor and a candidate for experimental manipulation using CRISPR-Cas method-based approaches.

• High-throughput fragment screening for TREM2 modulators: A 2026 Bioorganic & Medicinal Chemistry study used high-throughput fragment screening to identify new small-molecule scaffolds that bind TREM2 41793968Mar. The authors described TREM2 as a relevant target in neurodegenerative diseases and cancer immunotherapy, indicating that direct pharmacologic modulation of TREM2 signaling remains an active area of drug discovery.

• Microglial efferocytosis dysfunction after chronic sleep deprivation: A 2026 Journal of Affective Disorders study found that chronic sleep deprivation markedly impaired microglial efferocytosis and was associated with selective downregulation of TREM2 expression in aged mice 41785918Mar. This supports a role for TREM2 in maintaining microglial clearance functions and suggests that reduced TREM2 may contribute to depression-like behaviors and cognitive impairment under chronic stress conditions.

What Changes, What Holds

1. TREM2 is being positioned as a modifiable node in post-ischemic neuroprotection
NEW DIRECTION Elamipretide plus NMN extends TREM2 beyond its established roles in innate immune sensing and neurodegeneration by tying it to injury-recovery signaling after brain ischemia 42443448Jul. The baseline already allows TREM2 in neuroinflammatory regulation, so this does not overturn the account; it instead suggests that TREM2-mediated pathways may be therapeutically leveraged in acute brain injury, though the evidence is preclinical and needs replication and mechanistic separation from broader mitochondrial effects.

2. Iron availability emerges as a constraint on TREM2-linked macrophage function in diseased liver
NEW DIRECTION Fe2+ dependence adds a metabolic layer to the liver-disease story without displacing the established view that TREM2 marks disease-associated macrophage remodeling in MASH 42310295Jun. What changes is the mechanism: TREM2 expression is not just a marker of macrophage state but may be limited by iron homeostasis, with consequences for mitochondrial competence and Kupffer-cell function. That makes iron biology a plausible upstream regulator, but it remains unsettled whether this is a driver, a consequence, or both.

3. Epigenetic lactylation strengthens the case that TREM2high macrophages are fibrogenic effectors
REINFORCES H4K12 lactylation does not alter the baseline claim that TREM2-expressing macrophage subsets contribute to liver fibrosis; it sharpens that account by offering a route into TREM2high differentiation 42307631Jun. The main implication is mechanistic: fibrogenic macrophage states may be actively programmed rather than merely recruited. This supports TREM2 as part of the scar-associated macrophage program, but it does not by itself establish whether targeting this axis would reverse fibrosis in patients.

4. Common TREM2 variants remain consistent with a microglial risk mechanism in Alzheimer’s disease
REINFORCES R47H and R62H fit squarely within the established Alzheimer’s disease association of TREM2 and its importance in microglial biology 42298074Jun. The new work strengthens the idea that multiple functional roles of TREM2 in microglia can be perturbed by risk variants, rather than introducing a different disease class or use. It reinforces the baseline risk-marker framing, while leaving open which microglial functions are most decisive and how variant effects translate into pathology.

5. TREM2 is moving from a genetic risk marker toward an experimental editing target in Alzheimer’s disease models
NEW DIRECTION Gene-editing discussion adds a use case not covered by the baseline: manipulating TREM2 itself as a therapeutic or experimental lever in Alzheimer’s disease 41926312Apr. That does not contradict its role as a risk-associated immune regulator, but it shifts attention from association to intervention, including iPSC-based modeling and CRISPR-Cas approaches. The practical meaning is still speculative, and the key unresolved issue is whether editing TREM2 can improve function without disrupting protective microglial responses.

6. Direct small-molecule targeting of TREM2 is becoming more plausible as a drug-discovery strategy
REINFORCES Fragment screening does not change what TREM2 is known to do; it supports the existing view that TREM2 is a therapeutic target by showing that it can be engaged chemically 41793968Mar. The baseline already says TREM2 is being explored as a target, so this is an extension of drug discovery rather than a new biological role. The important takeaway is feasibility, not efficacy: binding scaffolds are a starting point, but functional modulation and disease benefit remain to be demonstrated.

7. Reduced TREM2 may help explain impaired microglial clearance under chronic stress
NEW DIRECTION Chronic sleep deprivation links TREM2 to a context the baseline does not cover: stress-related impairment of microglial efferocytosis and behavioral outcomes 41785918Mar. This leaves the established neurodegeneration and liver-disease account intact while broadening TREM2’s relevance to aging, sleep loss, and depression-like phenotypes. The result suggests that loss of TREM2 can be functionally harmful outside classic inflammatory disease, but causality and reversibility still need direct testing.

Overview update candidates: iron-dependent regulation of TREM2 in MASH/Kupffer cells; epigenetic control of TREM2high macrophage differentiation in liver fibrosis; TREM2 as an experimental gene-editing target in Alzheimer’s disease; reduced TREM2 in chronic sleep deprivation-associated microglial dysfunction.