Mechanism Research Of GPS2 Regulation In Angiogenesis

Angiogenesis is not only an essential process during development, but also plays an indispensable role in pathological process such as wound healing, diabetic retinopathy, rheumatoid arthritis and tumorigenesis. This process is tightly regulated by a very sensitive interplay of growth factors and inhibitors, in which a number of signaling pathways are also involved. Identification of key regulators in angiogenesis may provide new possibility for pro- or anti-angiogenesis treatments.GPS2 is a suppressor of G protein – MAPK signaling pathway, which is highly conserved in different species, such as human, mouse, rat, and zebrafish. The protein sequences of GPS2 are highly similar in human and mouse, with a difference of only 8out of the 327 amino acids. GPS2 is mainly localized in the nucleus and there is also a small distribution in the cytoplasm. GPS2 is necessary for the assemble of NCOR/SMRT complex in the nucleus, inhibiting the activity of some transcription factors like NF-κB and AP1. However, GPS2 can also perform as a transcriptional co-activator through binding with p300, promoting the activity of p53 and HNF4α. In the cytoplasm, GPS2 can specifically suppress JNK activation through inhibiting TRAF2/Ubc13 enzymatic activity. GPS2 is widely expressed in many tissues and cells,participating in the regulation of several biological processes in a transcription-dependent or nondependent regulatory manner, such as inflammation, bile acid synthesis, obesity, cholesterol metabolism, insulin resistance and so on.However, the function of GPS2 in vascular development is still unclear.In this study, we constructed the GPS2 knockout mouse and did a systematical study on its phenotype, especially focusing on the angiogenesis. We found that about50% mice lacking GPS2 die at embryonic day 10.5(E10.5d), and no one can survival beyond E14.5d. At E9.5d and E10.5d,GPS2 was universally expressed in the whole embryo by in situ hybridization and whole mount immunostaining. Highly expressed GSP2 was detected in E9.5d yolk sac by real-time PCR. The GPS2 deficient embryos were developmentally retarded. Abnormal vascular development was observed in the yolk sac and the head of the mutant embryos. Major vitelline vessels were narrower and underdeveloped in the mutant, and mutant yolk sac microvessels were more primitive,comprising disorganized capillary plexuses with larger intercapillary spaces than in the controls. Similarly, head capillaries were more primitive, and the head veins were narrower compared with controls. Most key factors of the VEGF, PDGF, Notch, and ANG pathways were down regulated in the mutant embryos at E9.5d. In vitro studies were performed in human umbilical vein endothelial cells(HUVECs), with the observation that knockdown of GPS2 suppressed migration and tube formation of HUVEC. These results suggested that GPS2 has an essential role in angiogenesis.Taken together, mice lacking GPS2 died between E10.5d and E 14.5d, with severe vascular developmental disorders in yolk sac and head. GPS2 deficiency inhibited a variety of angiogenesis related signaling pathways. Knockdown of GPS2 suppressed migration and tube-formation capability of HUVEC. This study will broaden the knowledge of biological function of GPS2, as well as discover novel mechanisms in the regulation of vascular development.