TREM2 Overexpression Lysate

HEK293T cells in 10-cm dishes were transiently transfected with a non-lipid polymer transfection reagent specially designed and manufactured for large volume DNA transfection. Transfected cells were cultured for 48hrs before collection. The cells were lysed in modified RIPA buffer (25mM Tris-HCl pH7.6, 150mM NaCl, 1% NP-40, 1mM EDTA, 1xProteinase inhibitor cocktail mix, 1mM PMSF and 1mM Na3VO4, and then centrifuged to clarify the lysate. Protein concentration was measured by BCA protein assay kit.

Triggering receptor expressed on myeloid cells-2 (TREM2) is a cell surface transmembrane glycoprotein receptor belonging to the immunoglobulin (Ig) subfamily that functions in pathology-induced immune system signaling (1). The TREM2 protein is encoded by the TREM2 gene located on chromosome 6p21.1 in humans and chromosome 17 in mouse (2). TREM2 is synthesized as a protein of 230 amino acids (aa) in length with a theoretic molecular weight (MW) of 25.4 kDa. TREM2 is comprised of a signaling peptide, an extracellular V-type Ig domain, a stalk region, a transmembrane helical domain, and a cytosolic tail (1-4). The receptor is expressed on cells of myeloid lineage including dendritic cells (DCs) and tissue-specific macrophages (e.g. microglia, osteoclasts) (2,3). There are several reported ligands for TREM2 such as bacterial components, lipoproteins, and apolipoproteins (1-3,5). Upon TREM2 receptor-ligand binding, the TREM2 protein interacts with adaptor proteins DNAX activation protein 12 (DAP12) and DAP10 (1-3,5). The TREM2-DAP12 complex leads to phosphorylation of DAP12's immunoreceptor tyrosine-based activation (ITAM) motif, followed by recruitment of Syk kinase, and activation of downstream signaling molecules such as phosphatidylinositol 3-kinase (PI3K), extracellular signal-regulated protein kinase (ERK), and phospholipase Cgamma (PLCgamma) (3,5). A soluble form of TREM2 (sTREM2) is generated by ectodomain shedding via a disintegrin and metalloproteinase 10 (ADAM10) and ADAM17, promoting survival and inflammation through the PI3K and nuclear factor kappa B (NFkappaB) pathways (2,5). TREM2 has been linked to myeloid maturation, proliferation, survival, phagocytosis, response to neurodegenerative cues, and regulation of inflammation (2,3).

TREM2 is upregulated under many pathological conditions and has been of particular interest in neurodegenerative disorders like Alzheimer's disease (AD) where it helps activate microglial responses (1-3,5). Studies have found that sTREM2 is typically elevated in the cerebral spinal fluid (CSF) of AD patients compared to healthy counterparts and may serve as a biomarker of AD (2). While TREM2-mediated microglial activation is considered beneficial in some disease contexts (e.g. demyelinating diseases, ischemia), it is detrimental in others (e.g. peripheral nerve injury) and may be dependent on disease stage, as observed in AD (2,5). Microglia promote amyloid-beta (Abeta) clearance, phagocytosis and reduce tau proliferation in the early stages of AD but can increase Abeta accumulation and tau propagation in late stages of AD (2). Recent studies have also suggested a role for TREM2 in cancer, where it supports an immune-suppressive tumor microenvironment such as reduced of T cell proliferation (1,6). Therapeutic targeting of the TREM2 pathway can be directed towards ligand binding to downstream signaling (1). Potential therapeutic strategies include using monoclonal antibodies or small molecules to either enhance or block signaling (1,6). While more work needs to be done, initial studies targeting TREM2 for cancer immunotherapy is promising (6).

References

1. Deczkowska A, Weiner A, Amit I. The Physiology, Pathology, and Potential Therapeutic Applications of the TREM2 Signaling Pathway. Cell. 2020; 181(6):1207-1217. https://doi.org/10.1016/j.cell.2020.05.003

2. Qin Q, Teng Z, Liu C, Li Q, Yin Y, Tang Y. TREM2, microglia, and Alzheimer's disease. Mech Ageing Dev. 2021; 195:111438. https://doi.org/10.1016/j.mad.2021.111438

3. Kober DL, Brett TJ. TREM2-Ligand Interactions in Health and Disease. J Mol Biol. 2017; 429(11):1607-1629. https://doi.org/10.1016/j.jmb.2017.04.004

4. Uniprot (Q9NZC2)

5. Konishi H, Kiyama H. Microglial TREM2/DAP12 Signaling: A Double-Edged Sword in Neural Diseases. Front Cell Neurosci. 2018; 12:206. https://doi.org/10.3389/fncel.2018.00206

This product is for research use only and is not approved for use in humans or in clinical diagnosis. Lysates are guaranteed for 6 months from date of receipt.

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