The Structure of a Full-length Membrane-embedded Integrin Bound to a Physiological Ligand

Dai, Aguang; Ye, Feng; Taylor, David; Hu, Guiqing; Ginsberg, Mark H.; Taylor, Kenneth A.

doi:10.1074/jbc.m115.682377

Cited by 34 publications

(34 citation statements)

References 53 publications

(89 reference statements)

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“…Upon activation, integrins extend into an elongated conformation in which the 2 subunits separate. 26 Growing evidence suggests that conformational changes in integrin require extracellular binding 27 in addition to cytoplasmic binders. For example, talin and kindlin binding to the integrin cytoplasmic domain was associated with an extended integrin conformation.…”

Section: Zooming Into Intact Platelets With Cryo-electron Tomographymentioning

confidence: 99%

Toward correlating structure and mechanics of platelets

Sorrentino

Studt

Horev

et al. 2016

Cell Adhesion & Migration

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The primary physiological function of blood platelets is to seal vascular lesions after injury and form hemostatic thrombi in order to prevent blood loss. This task relies on the formation of strong cellular-extracellular matrix interactions in the subendothelial lesions. The cytoskeleton of a platelet is key to all of its functions: its ability to spread, adhere and contract. Despite the medical significance of platelets, there is still no high-resolution structural information of their cytoskeleton. Here, we discuss and present 3-dimensional (3D) structural analysis of intact platelets by using cryoelectron tomography (cryo-ET) and atomic force microscopy (AFM). Cryo-ET provides in situ structural analysis and AFM gives stiffness maps of the platelets. In the future, combining highresolution structural and mechanical techniques will bring new understanding of how structural changes modulate platelet stiffness during activation and adhesion.

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Section: Zooming Into Intact Platelets With Cryo-electron Tomographymentioning

confidence: 99%

Toward correlating structure and mechanics of platelets

Sorrentino

Studt

Horev

et al. 2016

Cell Adhesion & Migration

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“…Models follow Ref. 59. B, sequence alignment of the ectodomain-linker-TM domain region of selected human integrin ␣ and ␤ subunits.…”

Section: Thermodynamic Description Of Ectodomain-tm Domainmentioning

confidence: 99%

A Conserved Ectodomain-Transmembrane Domain Linker Motif Tunes the Allosteric Regulation of Cell Surface Receptors

Schmidt

Situ

et al. 2016

Journal of Biological Chemistry

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In many families of cell surface receptors, a single transmembrane (TM) ␣-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 ␣IIb in model constructs and relate it to other integrin ␣ 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 ␤ 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.Cells sense their environment through transmembrane (TM) 3 surface receptors that transmit extracellular signals into the cell. With the exception of G-protein coupled receptors, these proteins are dimers composed of subunits that each typically exhibits an extracellular domain (ectodomain) containing the ligand-binding site, a single TM ␣-helix, and an intracellular effector domain. Integrins, which control vital cell-cell and cellmatrix adhesions (1-3), constitute one ubiquitous family of TM cell surface receptors. Receptor-tyrosine kinases represent another prominent family that activate upon the stabilization of dimeric receptor states by bound ligand (4, 5). However, rather than being simple binary switches, all these receptors have the potential for allosteric regulation (1, 5, 6), indicating a multistate coupling of ecto-and TM domains. This coupling and associated allosteric parameters must depend on the structural and dynamic properties of the linker between ecto-and TM domains. However, irrespective of detailed structural information on ecto-and TM domain in receptor-tyrosine kinases (4, 5), structural or dynamic information on linkers remains indirect and ambiguous (7-9). Similarly, structures of integrin ectodomains, TM domains, and cytosolic tails are available (10 -16) but little is known about their ecto-TM domain coupling. In support of a functionally relevant linker, integrin ␣M␤2 spontaneously activates when the TM domain is uncoupled from the ectodomain by insertion of a flexible (GGGGS) 2 linker (17).Integrins consist of heterodimeric, non-covalently associated ␣␤ subunits that each exhibits a large ectodomain, a single TM ␣-helix, and a short cytosolic tail (Fig. 1A). In addition to outside-in signaling, integrins also signal in the opposite direction (inside-out signaling) in relationship to their function as dynamic c...

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“…For many integrin members, a process of activation is required for them to be able to interact with soluble ligands, via conformational changes from a quiescent/bent state to an active/extended state, i.e. inside-out signaling (Dai et al, 2015;Ginsberg et al, 2005). The activation states of integrins are tightly controlled by interactions between α-and β-subunits at both the membrane-proximal cytoplasmic tails (CTs) and the transmembrane domains (Vinogradova et al, 2002;Yang et al, 2009;Zhu et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Kindlin supports platelet integrin αIIbβ3 activation by interacting with paxillin

Gao

Huang

Lai

et al. 2017

Journal of Cell Science

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Kindlins play an important role in supporting integrin activation by cooperating with talin; however, the mechanistic details remain unclear. Here, we show that kindlins interacted directly with paxillin and that this interaction could support integrin αIIbβ3 activation. An exposed loop in the N-terminal F 0 subdomain of kindlins was involved in mediating the interaction. Disruption of kindlin binding to paxillin by structure-based mutations significantly impaired the function of kindlins in supporting integrin αIIbβ3 activation. Both kindlin and talin were required for paxillin to enhance integrin activation. Interestingly, a direct interaction between paxillin and the talin head domain was also detectable. Mechanistically, paxillin, together with kindlin, was able to promote the binding of the talin head domain to integrin, suggesting that paxillin complexes with kindlin and talin to strengthen integrin activation. Specifically, we observed that crosstalk between kindlin-3 and the paxillin family in mouse platelets was involved in supporting integrin αIIbβ3 activation and in vivo platelet thrombus formation. Taken together, our findings uncover a novel mechanism by which kindlin supports integrin αIIbβ3 activation, which might be beneficial for developing safer anti-thrombotic therapies.

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The Structure of a Full-length Membrane-embedded Integrin Bound to a Physiological Ligand

Cited by 34 publications

References 53 publications

Toward correlating structure and mechanics of platelets

Toward correlating structure and mechanics of platelets

A Conserved Ectodomain-Transmembrane Domain Linker Motif Tunes the Allosteric Regulation of Cell Surface Receptors

Kindlin supports platelet integrin αIIbβ3 activation by interacting with paxillin

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