DEPTOR Deficiency-Mediated mTORc1 Hyperactivation in Vascular Endothelial Cells Promotes Angiogenesis

Abstract

Background/Aims: The mechanistic target of rapamycin (mTOR) signaling pathway is essential for angiogenesis and embryonic development. DEP domain-containing mTOR-interacting protein (DEPTOR) is an mTOR binding protein that functions to inhibit the mTOR pathway In vitro experiments suggest that DEPTOR is crucial for vascular endothelial cell (EC) activation and angiogenic responses. However, knowledge of the effects of DEPTOR on angiogenesis in vivo is limited. This study aimed to determine the role of DEPTOR in tissue angiogenesis and to elucidate the molecular mechanisms. Methods: Cre/loxP conditional gene knockout strategy was used to delete the Deptor gene in mouse vascular ECs. The expression or distribution of cluster of differentiation 31 (CD31), vascular endothelial growth factor (VEGF) and hypoxia inducible factor-1 alpha (HIF-1α) were detected by immunohistochemical staining or western blot. Tube formation assay was used to measure angiogenesis in vitro. Results: Deptor knockdown led to increased expression of CD31, VEGF and HIF-1α in heart, liver, kidney and aorta. After treatment with rapamycin, their expression was significantly down regulated. In vitro, human umbilical vein endothelial cells (HUVECs) were transfected with DEPTOR-specific small interfering RNA (siRNA), which resulted in a significant increase in endothelial tube formation and migration rates. In contrast, DEPTOR overexpression markedly reduced the expression of CD31, VEGF and HIF-1α. Conclusions: Our findings demonstrated that deletion of the Deptor gene in vascular ECs resulted in upregulated expression of CD31 and HIF-1α, and further stimulated the expression of VEGF which promoted angiogenesis, indicating that disruption of normal angiogenic pathways may occur through hyperactivation of the mTORC1/HIF-1α/VEGF signaling pathway.

Amino acid transporter LAT1 in tumor-associated vascular endothelium promotes angiogenesis by regulating cell proliferation and VEGF-A-dependent mTORC1 activation

“…In this study, we demonstrated that LAT1 is indispensable for VEGF-A-dependent activation of mTORC1 (Fig. 7), which plays key roles in the cellular processes such as migration and tube formation in vitro as well as in in vivo angiogenesis [50][51][52][53]. Our results suggest that the roles of LAT1 in the activation of mTORC1 is mediated by Ragulator-Rag complex that is independent of RTK-PI3K-Akt axis.…”

Revisiting PI3-kinase signalling in angiogenesis

“…The generation of constitutive knockout mice of several components of mTORC1 and mTORC2 have contributed in establishing a central role of this hub in a regulation of fundamental organismal functions, including angiogenesis ( 24 ). Indeed, endothelial-specific deletion of several components of mTORC has shed light onto the autonomous role of mTOR cell in the vessel growth ( 25 , 26 ). However, this is still insufficient to fully understand how and in which contexts mTOR regulates angiogenesis.…”

The SWELL1-LRRC8 complex regulates endothelial AKT-eNOS-mTOR signaling and vascular function

“…Supplementary Table 1&2). Also, notable are statistically significant increases in VEGFA (1.6fold) and CD31 (2.0-fold) expression in SWELL1 KD HUVECs, both of which are pro-angiogenic and associated with mTORC1 hyperactivation (47). Pathways linked to cell adhesion and reninangiotensin signaling are also enriched -both pathways and processes that are known to be altered in vasculature in the setting of atherosclerosis and Type 2 diabetes (T2D).…”