title: A Conserved Ectodomain-Transmembrane Domain Linker Motif Tunes the Allosteric Regulation of Cell Surface Receptors.
abstract: In many families of cell surface receptors, a single transmembrane (TM) α-helix separates ecto- and cytosolic domains. A defined coupling of ecto- and TM domains must be essential to allosteric receptor regulation but remains little understood. Here, we characterize the linker structure, dynamics, and resulting ecto-TM domain coupling of integrin αIIb in model constructs and relate it to other integrin α subunits by mutagenesis. Cellular integrin activation assays subsequently validate the findings in intact receptors. Our results indicate a flexible yet carefully tuned ecto-TM coupling that modulates the signaling threshold of integrin receptors. Interestingly, a proline at the N-terminal TM helix border, termed NBP, is critical to linker flexibility in integrins. NBP is further predicted in 21% of human single-pass TM proteins and validated in cytokine receptors by the TM domain structure of the cytokine receptor common subunit β and its P441A-substituted variant. Thus, NBP is a conserved uncoupling motif of the ecto-TM domain transition and the degree of ecto-TM domain coupling represents an important parameter in the allosteric regulation of diverse cell surface receptors.
authors.affiliation: From the Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schmidt
authors.affiliation: the Department of Medicine, University of California San Diego, La Jolla, California 92093, and.
authors.forename: Feng
authors.initials: F
authors.lastname: Ye
authors.affiliation: From the Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Situ
authors.affiliation: the Department of Biochemistry & Molecular Biology and Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, California 90033.
authors.forename: Woojin
authors.initials: W
authors.lastname: An
authors.affiliation: the Department of Medicine, University of California San Diego, La Jolla, California 92093, and.
authors.forename: Mark H
authors.initials: MH
authors.lastname: Ginsberg
authors.affiliation: From the Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, tulmer@usc.edu.
authors.forename: Tobias S
authors.initials: TS
authors.lastname: Ulmer
mesh_terms: D000494:Allosteric Regulation / Q000502:physiology; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D053648:Cytokine Receptor Common beta Subunit / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D039641:Integrin beta Chains / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000072417:Protein Domains; D017433:Protein Structure, Secondary
chemical_list: D053648:Cytokine Receptor Common beta Subunit; D039641:Integrin beta Chains
keywords: allosteric regulation; cytokine; integrin; isothermal titration calorimetry (ITC); nuclear magnetic resonance (NMR); protein dynamics; receptor signaling; transmembrane cell surface receptors