Fig. 4

TREM2 signaling and function. TREM2 has been proposed to bind to a variety of different ligands, categorized here by lipids, lipoproteins and ligands associated with damage- or pathogen-related molecular patterns. These ligands bind to the TREM2 receptor. Following ligand binding, TREM2 can associate with DAP12 homodimers or DAP12/DAP10 heterodimers to mediate downstream signaling. This signaling requires phosphorylation of the adaptor, following which activating (shown on left in green) or inhibitory (shown on right in red) signaling components can bind. These activating components have been shown to initiate different downstream pathways that lead to cell proliferation and differentiation, survival, phagocytosis, chemotaxis and inflammation. While many other signaling components are thought to play a role downstream of TREM2 activation, only those validated as part of the signaling pathway responsible for the listed functions have been included here. Association with inhibitory components is thought to prevent activation of these downstream pathways. Lipids: PE [254, 96], PS [96, 144, 196, 222, 254], PA [96, 222, 254], PG [254, 222, 96], PC [144, 196, 222, 96, 254], PI [196, 222, 96], CL [96, 254, 222], SM [196, 222, 96, 254], LA [254, 222], SA [144, 196, 222, 96], Apo-/lipoproteins: ApoE [95, 96, 94], ApoJ [94], ApoA-1 [94, 96], ApoA-II [94, 96], LDL, HDL [94, 144, 93], PAMP/DAMPs: [244, 245], (−) bacterial products (LPS, LTA) [244], Nucleic Acids [160], Heat Shock protien 60 [249], Apoptotic cells [95, 153, 160, 96, 222], Macropahages [252], Astrocytoma cells [244]