Fig. 5
BCAAs and BCKAs suppress TREM2 activation through binding to TREM2. A Molecular docking results of L-Leucine and KICA binding to TREM2 extracellular domain. B Biolayer interferometry (BLI) analysis of interaction of BCAAs or BCKAs with TREM2. BCAAs and BCKAs was titrated from 15.63 to 500 μM and 31.25 to 500 μM, respectively. C LC–MS/MS spectra of TREM2 immunoprecipitated L-Leucine-13C of BV2 cells after BCAAs isotope treatment for 1 h. D Thermal stabilization of TREM2 protein evaluated by cellular thermal shift assay (CETSA) after treating BV2 cells with BCAAs/ BCKAs for 4 h (n = 3). E Representative images of binding of fluorescein labeled-Aβ to cell surface TREM2 in BV2 cells after treatment of BCAAs/ BCKAs for 2 h (n = 3, Scale bars, 40 μm). F Representative images of microglial phagocytosis of fluorescein labeled-Aβ in BV2 cells after treatment of BCAAs/ BCKAs in the presence or absence of S1P for 4 h (n = 3, Scale bars, 40 μm). G Western blot analysis of phosphorylation levels of SYK in BV2 cell after treatment of BCAAs/ BCKAs in the presence or absence of sphingosine-1-phosphate (S1P) for 4 h (n = 3). Data in D, E, F and G are means ± SEM. *P < 0.05,**P < 0.01 and ***P < 0.001, one-way ANOVA, followed by Tukey’s multiple comparisons test