Down syndrome candidate region 1-like 1 (DSCR1-L1) mimics the inhibitory effects of DSCR1 on calcineurin signaling in endothelial cells and inhibits angiogenesis

摘要

In endothelial cells, binding of vascular endothelial growth factor (VEGF) to VEGF receptor 2 (VEGFR-2) leads to the activation of the serine/threonine phosphatase calcineurin, dephosphorylation of the NF-AT transcription factors, translocation of NF-AT to the nucleus, and expression of angiogenesis-related genes such as Cox-2. Down syndrome candidate region 1 (DSCR1) is transactivated by NF-AT nuclear translocation, and in turn inhibits calcineurin activity, forming a negative feedback loop. While DSCR1 has a clearly defined role as an endogenous inhibitor of VEGF-calcineurin mediated angiogenesis in endothelial cells, the function of the DSCR1 family member, DSCR1-like1 (DSCR1-L1) has not yet been investigated in endothelial cells. Here we show that a panel of proangiogenic factors including VEGF, basic fibroblast growth factor (bFGF), angiopoietin 1 (Ang1), hepatocyte growth factor (HGF) as well as triiodo-L-thyronine (T3) does not induce DSCR1-L1 upregulation in endothelial cells while VEGF potently upregulates DSCR1. To investigate the effects of DSCR1-L1 on endothelial cell function, we cloned the gene into a lentiviral vector and over-expressed DSCR1-L1 in human umbilical vein endothelial cells (HUVEC). Constitutive DSCR1-L1 over-expression prevented the nuclear translocation of NF-ATc1 in response to VEGF, underscoring its role as a calcineurin inhibitor. Additionally, DSCR1-L1-transduced cells inhibited VEGF-induced endothelial cell migration, proliferation, and tube formation by 36%, 77%, and 39%, respectively, compared to cells infected with control virus. Over-expression of DSCR1-L1 in the transformed endothelial cell line SVR also resulted in decreased proliferation. Our findings demonstrate that DSCR1-L1 is constitutively expressed in endothelial cells and acts similar to DSCR1 in inhibiting calcineurin activity and restraining VEGF-mediated angiogenesis.