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Structural characterisation of a novel GPVI nanobody-complex reveals a biologically active domain-swapped GPVI dimer

DOI: 10.1182/blood.2020009440 DOI Help

Authors: Alexandre Slater (University of Birmingham) , Ying Di (University of Birmingham) , Joanne C Clark (Centre of Membrane Proteins and Receptors (COMPARE)) , Natalie Jasmin Jooss (Maastricht University) , Eleyna M Martin (University of Birmingham) , Fawaz Obaidullah Alenazy (University of Birmingham) , Mark R. Thomas (University of Birmingham) , Robert A. S. Ariƫns (University of Leeds) , Andrew B. Herr (Cincinnati Children's Hospital Medical Center) , Natalie S. Poulter (Centre of Membrane Proteins and Receptors (COMPARE)) , Jonas Emsley (Centre of Membrane Proteins and Receptors (COMPARE)) , Stephen P. Watson (Centre of Membrane Proteins and Receptors (COMPARE)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Blood

State: Published (Approved)
Published: January 2021
Diamond Proposal Number(s): 19880

Abstract: GPVI is the major signalling receptor for collagen on platelets. We have raised 54 nanobodies (Nb), grouped into 33 structural classes based on their complementary determining region 3 (CDR3) loops, against recombinant GPVI-Fc (dimeric GPVI) and have characterised their ability to bind recombinant GPVI, resting and activated platelets, and to inhibit platelet activation by collagen. Nanobodies from six different binding classes showed the strongest binding to recombinant GPVI-Fc suggesting that there was not a single dominant class. The most potent three, Nb2, 21 and 35, inhibited collagen-induced platelet aggregation with nanomolar IC50 values and inhibited platelet aggregation under flow. The binding KD of the most potent Nb, Nb2, against recombinant monomeric and dimeric GPVI was 0.6 and 0.7 nM, respectively. The crystal structure of monomeric GPVI in complex with Nb2 revealed a binding epitope adjacent to the CRP binding groove within the D1 domain. In addition, a novel conformation of GPVI involving a domain swap between the D2 domains was observed. The domain swap is facilitated by the outward extension of the C-C' loop which forms the domain swap hinge. The functional significance of this conformation was tested by truncating the hinge region so that the domain swap cannot occur. Nb2 was still able to displace collagen and CRP binding to the mutant, but signalling was abolished in a cell-based NFAT-reporter assay. This demonstrates that the C-C' loop region is important for GPVI signalling but not ligand binding and suggests the domain-swapped structure may represent an active GPVI conformation.

Journal Keywords: binding (molecular function); blood platelets; collagen; communication-and-resolution programs; c-reactive protein; crystal structure; cyclic amp receptor protein; dimers; epitopes; epley maneuver

Subject Areas: Biology and Bio-materials

Instruments: I04-Macromolecular Crystallography

Added On: 03/02/2021 08:39

Discipline Tags:

Biochemistry Chemistry Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Macromolecular Crystallography (MX)