title: Effects of the association between the α-subunit thigh and the β-Subunit EGF2 domains on integrin activation and signaling.
abstract: Integrin bidirectional signaling is mediated by conformational change. It has been shown that the separation of the α- and β-subunit transmembrane/cytoplasmic tails and the lower legs is required for transmitting integrin bidirectional signals across the plasma membrane. In this study, we address whether the separation of the αβ knee is critical for integrin activation and outside-in signaling. By introducing three disulfide bonds to restrict dissociation of the α-subunit thigh domain and β-subunit I-EGF2 domain, we found that two of them could completely abolish integrin inside-out activation, whereas the other could not. This disulfide-bonded mutant, in the context of the activation mutation of the cytoplasmic domain, had intermediate affinity for ligands and was able to mediate cell adhesion. Our data suggest that there exists rearrangement at the interface between the thigh domain and the I-EGF2 domain during integrin inside-out activation. None of the disulfide-bonded mutants could mediate cell spreading upon adhering to immobilized ligands, suggesting that dissociation of the integrin two knees is required for integrin outside-in signaling. Disrupting the interface by introducing a glycan chain into either subunit is sufficient for high affinity ligand binding and cell spreading.
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Yan
authors.initials: Y
authors.lastname: Jiang
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
authors.forename: Bing-Hao
authors.initials: BH
authors.lastname: Luo
mesh_terms: D002448:Cell Adhesion; D002460:Cell Line; D002465:Cell Movement; D015870:Gene Expression; D006801:Humans; D039001:Integrin alpha Chains / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D039641:Integrin beta Chains / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D015398:Signal Transduction
chemical_list: D039001:Integrin alpha Chains; D039641:Integrin beta Chains; D008024:Ligands