Faculty Collaboration Database

Autonomous conformational regulation of β₃ integrin and the conformation-dependent property of HPA-1a alloantibodies. Proc Natl Acad Sci U S A 2018 Sep 25;115(39):E9105-E9114

Date

09/14/2018

Pubmed ID

30209215

Pubmed Central ID

PMC6166792

DOI

10.1073/pnas.1806205115

Scopus ID

2-s2.0-85054028338 (requires institutional sign-in at Scopus site)   20 Citations

Abstract

Integrin α/β heterodimer adopts a compact bent conformation in the resting state, and upon activation undergoes a large-scale conformational rearrangement. During the inside-out activation, signals impinging on the cytoplasmic tail of β subunit induce the α/β separation at the transmembrane and cytoplasmic domains, leading to the extended conformation of the ectodomain with the separated leg and the opening headpiece that is required for the high-affinity ligand binding. It remains enigmatic which integrin subunit drives the bent-to-extended conformational rearrangement in the inside-out activation. The β₃ integrins, including α_IIbβ₃ and α_Vβ₃, are the prototypes for understanding integrin structural regulation. The Leu33Pro polymorphism located at the β₃ PSI domain defines the human platelet-specific alloantigen (HPA) 1a/b, which provokes the alloimmune response leading to clinically important bleeding disorders. Some, but not all, anti-HPA-1a alloantibodies can distinguish the α_IIbβ₃ from α_Vβ₃ and affect their functions with unknown mechanisms. Here we designed a single-chain β₃ subunit that mimics a separation of α/β heterodimer on inside-out activation. Our crystallographic and functional studies show that the single-chain β₃ integrin folds into a bent conformation in solution but spontaneously extends on the cell surface. This demonstrates that the β₃ subunit autonomously drives the membrane-dependent conformational rearrangement during integrin activation. Using the single-chain β₃ integrin, we identified the conformation-dependent property of anti-HPA-1a alloantibodies, which enables them to differently recognize the β₃ in the bent state vs. the extended state and in the complex with α_IIb vs. α_V This study provides deeper understandings of integrin conformational activation on the cell surface.

Author List

Thinn AMM, Wang Z, Zhou D, Zhao Y, Curtis BR, Zhu J

Authors

Brian Curtis PhD Director in the Platelet & Neutrophil Immunology Laboratory department at BloodCenter of Wisconsin
Jieqing Zhu PhD Assistant Professor, Associate Investigator in the Biochemistry department at BloodCenter of Wisconsin

MESH terms used to index this publication - Major topics in bold

Antibody Specificity
Crystallography, X-Ray
Glucuronidase
HEK293 Cells
Humans
Integrin alphaVbeta3
Integrin beta3
Isoantibodies
Platelet Glycoprotein GPIIb-IIIa Complex
Protein Domains
Protein Folding