Fig. 6: BIEGi-1 suppresses cancer cell growth.
From: Lysosomal EGFR acts as a Rheb-GEF independent of its kinase activity to activate mTORC1
a Chemical structure of BIEGi-1. b Structural model of EGFR-TKD complexed with BIEGi-1. EGFR-TKD is shown in surface representation and BIEGi-1 in ball-and-stick. The ATP-binding site (orange) and predicted Rheb-GEF interface (blue) of EGFR are indicated. c BIEGi-1 impairs the EGFR-mediated Rheb nucleotide exchange. An in vitro guanine nucleotide exchange assay was performed using purified Rheb and EGFR-TKD-WT with the addition of erlotinib, afatinib or BIEGi-1 and analyzed as described in Fig. 3f. d BIEGi-1 abolishes the interaction between EGFR and Rheb in cells. PC9 cells treated with or without 25 nM BIEGi-1 for 12 h were subjected to immunoprecipitation and analyzed by western blotting. e BIEGi-1 inhibits mTORC1 activation in EGFR-mutated cells. PC9 and HCC827 cells were treated with 25 nM erlotinib, afatinib, or BIEGi-1 for 12 h as indicated, and analyzed by western blotting. f CCK8 assays of PC-9 and HCC827 cells exposed to BIEGi-1. The IC50 values were 17 nM and 20 nM for PC9 and HCC827 cells, respectively. Data points represent the means ± SD (n = 3). g BIEGi-1 and afatinib, but not erlotinib, inhibit the activation of mTORC1 induced by LAMP2-V5-EGFR-TKD. HEK-293T cells stably expressing the indicated plasmids were serum-starved, treated with 200 nM BIEGi-1, erlotinib or afatinib for 24 h, and analyzed by western blotting. WT and KD refer to LAMP2-V5-EGFR-TKD-WT and LAMP2-V5-EGFR-TKD-KD, respectively. h Model illustrating that lysosomal EGFR acts as a GEF for Rheb, with Glu804 serving as a glutamic finger to activate mTORC1. Inhibition of both GEF and kinase activities of EGFR by BIEGi-1 restricts mTORC1 activity, leading to impaired cell growth.
