title: Domain and functional analysis of a novel platelet-endothelial cell surface protein, SCUBE1.
abstract: SCUBE1 (signal peptide-CUB-EGF domain-containing protein 1) is a novel, secreted, cell surface glycoprotein expressed during early embryogenesis and found in platelet and endothelial cells. This protein is composed of an N-terminal signal peptide sequence followed by nine tandemly arranged epidermal growth factor (EGF)-like repeats, a spacer region, three cysteine-rich repeat motifs, and one CUB domain at the C terminus. However, little is known about its domain and biological function. Here, we generated a comprehensive panel of domain deletion constructs and a new genetic mouse model with targeted disruption of Scube1 (Scube1(Delta cub/Delta cub)) to investigate the domain function and biological significance. A number of cell-based assays were utilized to define the critical role of the spacer region for membrane association and establish that the EGF-like repeats 7-9 are sufficient for the formation of SCUBE1-mediated homophilic adhesions in a calcium-dependent fashion. Biochemical and molecular analyses showed that the C-terminal cysteine-rich motifs and CUB domain could directly bind and antagonize the bone morphogenetic protein activity. Furthermore, genetic ablation of this C-terminal region resulted in brain malformation in the Scube1(Delta cub/Delta cub) embryos. Together, our results support the dual roles of SCUBE1 on brain morphogenesis and cell-cell adhesions through its distinct domain function.
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, 128 Academia Road, Sec. 2, Taipei 115.
authors.forename: Cheng-Fen
authors.initials: CF
authors.lastname: Tu
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Yan
authors.forename: Szu-Yao
authors.initials: SY
authors.lastname: Wu
authors.forename: Bambang
authors.initials: B
authors.lastname: Djoko
authors.forename: Ming-Tzu
authors.initials: MT
authors.lastname: Tsai
authors.forename: Chien-Jui
authors.initials: CJ
authors.lastname: Cheng
authors.forename: Ruey-Bing
authors.initials: RB
authors.lastname: Yang
mesh_terms: D020816:Amino Acid Motifs; D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism*; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors; D002135:Calcium-Binding Proteins; D002449:Cell Aggregation; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D042783:Endothelial Cells / Q000166:cytology* / Q000378:metabolism*; D018390:Gene Targeting; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism*; D008636:Mesencephalon / Q000473:pathology; D009436:Neural Tube Defects / Q000473:pathology; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D020449:Repetitive Sequences, Amino Acid; D017384:Sequence Deletion; D013329:Structure-Activity Relationship
chemical_list: D019485:Bone Morphogenetic Proteins; D002135:Calcium-Binding Proteins; D036341:Intercellular Signaling Peptides and Proteins; C417547:Scube1 protein, mouse