Inhibition of endothelial cell activation by bHLH protein E2-2 and its impairment of angiogenesis

• Published in: Blood 2010-05, Vol.115 (20), p.4138-4147
• Main Authors: Tanaka, Aya, Itoh, Fumiko, Nishiyama, Koichi, Takezawa, Toshiaki, Kurihara, Hiroki, Itoh, Susumu, Kato, Mitsuyasu
• Format: Article
• Language: English
• Subjects: Animals; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors - genetics; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors - metabolism; Biological and medical sciences; Blotting, Western; Cells, Cultured; Chlorocebus aethiops; COS Cells; Embryo, Mammalian - cytology; Embryo, Mammalian - metabolism; Endothelium, Vascular - physiology; Fluorescent Antibody Technique, Indirect; Hematologic and hematopoietic diseases; Humans; Immunoprecipitation; Inhibitor of Differentiation Protein 1 - genetics; Inhibitor of Differentiation Protein 1 - metabolism; Medical sciences; Mice; Neovascularization, Pathologic - metabolism; Neovascularization, Pathologic - prevention & control; Promoter Regions, Genetic; Reverse Transcriptase Polymerase Chain Reaction; RNA, Small Interfering - pharmacology; TCF Transcription Factors - antagonists & inhibitors; TCF Transcription Factors - genetics; TCF Transcription Factors - metabolism; Transcription Factor 4; Transcription Factor 7-Like 2 Protein; Transcription, Genetic; Two-Hybrid System Techniques; Vascular Endothelial Growth Factor Receptor-2 - genetics; Vascular Endothelial Growth Factor Receptor-2 - metabolism
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2009-05-223057

E2-2 belongs to the basic helix-loop-helix (bHLH) family of transcription factors. E2-2 associates with inhibitor of DNA binding (Id) 1, which is involved in angiogenesis. In this paper, we demonstrate that E2-2 interacts with Id1 and provide evidence that this interaction potentiates angiogenesis. Mutational analysis revealed that the HLH domain of E2-2 is required for the interaction with Id1 and vice versa. In addition, Id1 interfered with E2-2–mediated effects on luciferase reporter activities. Interestingly, injection of E2-2–expressing adenoviruses into Matrigel plugs implanted under the skin blocked in vivo angiogenesis. In contrast, the injection of Id1-expressing adenoviruses rescued E2-2–mediated inhibition of in vivo angiogenic reaction. Consistent with the results of the Matrigel plug assay, E2-2 could inhibit endothelial cell (EC) migration, network formation, and proliferation. On the other hand, knockdown of E2-2 in ECs increased EC migration. The blockade of EC migration by E2-2 was relieved by exogenous expression of Id1. We also demonstrated that E2-2 can perturb VEGFR2 expression via inhibition of VEGFR2 promoter activity. This study suggests that E2-2 can maintain EC quiescence and that Id1 can counter this effect.