Endothelial CD146 is required for in vitro tumor-induced angiogenesis: the role of a disulfide bond in signaling and dimerization.
Tumor angiogenesis, induced by tumor-secreted pro-angiogenic factors, is an essential process for cancer development and metastasis. CD146 is identified as an endothelial cell adhesion molecule and implicated in blood vessel formation, however, its exact role in angiogenesis, particularly tumor angiogenesis, and its potential function of mediating downstream signaling are still unclear. In present study, we evidenced that silencing endogenous endothelial CD146 by RNAi significantly impaired hepatocarcinoma cell secretions-promoted tubular morphogenesis and -enhanced motility of endothelial cells. Biochemical studies revealed that CD146 was required for the activation of p38/IKK/NF kappaB signaling cascade and up-regulation of NF kappaB downstream pro-angiogenic genes, notably IL-8, ICAM-1 and MMP9, in response to tumor secretions. Interestingly, specific anti-CD146 mAb AA98, which bound a conformational epitope depending on C452-C499 disulfide bond, could abrogate NF kappaB activation and tumor angiogenesis, whereas another anti-CD146 mAb AA1 recognizing a linear epitope containing aa50-54 did not have such effects. Further structure-function analysis identified that C452-C499 disulfide bond within the fifth extracellular Ig domain was indispensible for CD146-mediated signaling and tube formation. Moreover, dimerization of CD146, which was enhanced by tumor secretions and suppressed by AA98 but not AA1, also relied on C452 and C499. Together, this study for the first time uncovered the pro-angiogenic role of CD146 and also pinpointed the key structural basis responsible for its signaling function and dimerization. These findings also suggested that CD146 might serve as not just a cell adhesion molecule but also a membrane signal receptor in tumor-induced angiogenesis.
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Chaogu
C
Zheng
Yijun
Y
Qiu
Qiqun
Q
Zeng
Ying
Y
Zhang
Di
D
Lu
Dongling
D
Yang
Jing
J
Feng
Xiyun
X
Yan
D043925:Angiogenesis Inducing Agents / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D051929:CD146 Antigen / Q000737:chemistry / Q000378:metabolism; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned / Q000494:pharmacology; D003545:Cysteine / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism*; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D018604:Epitope Mapping; D000939:Epitopes / Q000276:immunology; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D009024:Morphogenesis / Q000187:drug effects; D016328:NF-kappa B / Q000378:metabolism; D009369:Neoplasms / Q000098:blood supply* / Q000201:enzymology; D009389:Neovascularization, Pathologic / Q000378:metabolism*; D055503:Protein Multimerization / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013329:Structure-Activity Relationship; D015854:Up-Regulation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D043925:Angiogenesis Inducing Agents; D000911:Antibodies, Monoclonal; D051929:CD146 Antigen; D017077:Culture Media, Conditioned; D004220:Disulfides; D000939:Epitopes; C497902:MCAM protein, human; D016328:NF-kappa B; D051550:I-kappa B Kinase; D048051:p38 Mitogen-Activated Protein Kinases; D003545:Cysteine