Fig. 7

Effects of LAT1 knockdown and inhibition on VEGF-A-dependent signaling pathways. a HUVECs starved for serum and growth factors were stimulated with VEGF-A (10 ng/mL) in the presence or absence of JPH203 (50 μM). b and c Effects of JPH203 and rapamycin, and LAT1 KD on mTORC1- and GAAC pathways under stimulation with VEGF-A. HUVECs starved for serum and growth factors were stimulated with VEGF-A (10 ng/mL) for 20 min in the presence or absence of JPH203 (50 μM) or rapamycin (10 nM) (b). HUVECs transfected with control siRNA (NC) or LAT1-targeting siRNA (LAT1 siRNA #1) were starved and stimulated with VEGF-A (10 ng/mL) for 20 min (c). d Proposed molecular mechanism for the essential role of endothelial LAT1 in the VEGF-A-dependent activation of mTORC1. The LAT1-mediated amino acid signaling is independent of the PI3K-Akt axis in the downstream of VEGFR2, and is possibly mediated by Ragulator-Rag GTPase heterodimer complex that recruits inactive mTORC1 onto lysosomal surface for its interaction with kinase activator Rheb. The input of amino acid signaling is indispensable for the pro-angiogenic VEGF-A signaling to induce activation mTORC1 and subsequent angiogenesis