Adhesion-induced unclasping of cytoplasmic tails of integrin α IIbβ 3

Nataly Podolnikova, Timothy E. O'Toole, Thomas A. Haas, Stephen C T Lam, Joan E B Fox, Tatiana Ugarova

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Integrin α IIbβ 3 plays a pivotal role in hemostasis and thrombosis by mediating adhesive interactions of platelets. Binding of α IIbβ 3 to its physiological ligands, immobilized fibrinogen and fibrin, induces outside-in signaling in platelets, leading to their adhesion and spreading even without prior stimulation by agonists. Implicit in these phenomena is a requirement for the linkage between integrins' cytoplasmic tails and intracellular proteins. However, the nature of the initiating signal has not been established. In this study, we examined whether binding of α IIbβ 3 to immobilized fibrin(ogen), per se, triggers interaction of the integrin with cytoplasmic proteins. Using the integrin-binding skelemin fragment as a marker of exposure of residues involved in the clasp between α IIb and β 3 cytoplasmic tails, we showed that its binding site in the membrane-proximal β 3 715-730 segment is cryptic and becomes exposed as a result of binding of isolated α IIbβ 3 to immobilized ligands. Furthermore, the skelemin-like protein present in platelets and CHO cells does not associate with α IIbβ 3 in resting platelets or suspended α IIbβ 3-expressing CHO cells but is recruited to integrin during cell adhesion. In addition, not only β 3 but also the membrane-proximal 989-1000 segment of the α IIb cytoplasmic tail binds the skelemin fragment. Finally, the same residues, α 3 Val 990, α IIb Arg 995, and β 3 His 722, involved in the formation of the clasp between the tails are also required for skelemin binding. These studies suggest that ligation of α IIbβ 3 by immobilized ligands during platelet adhesion induces a transmembrane conformation change in the integrin, resulting in unclasping of the complex between the membrane-proximal parts of cytoplasmic tails, thereby unmasking residues involved in binding the skelemin-like protein. Thus, the junction between α IIb and β 3 cytoplasmic tails may contain the critical structural information for the initiation of outside-in signaling.

Original languageEnglish (US)
Pages (from-to)617-629
Number of pages13
JournalBiochemistry
Volume48
Issue number3
DOIs
StatePublished - Jan 27 2009

Fingerprint

Connectin
Integrins
Platelets
Adhesion
Blood Platelets
CHO Cells
Ligands
Fibrin
Membranes
Proteins
Cell adhesion
Hemostasis
Cell Adhesion
Adhesives
Fibrinogen
Ligation
Conformations
Thrombosis
Binding Sites

ASJC Scopus subject areas

  • Biochemistry

Cite this

Adhesion-induced unclasping of cytoplasmic tails of integrin α IIbβ 3 . / Podolnikova, Nataly; O'Toole, Timothy E.; Haas, Thomas A.; Lam, Stephen C T; Fox, Joan E B; Ugarova, Tatiana.

In: Biochemistry, Vol. 48, No. 3, 27.01.2009, p. 617-629.

Research output: Contribution to journalArticle

Podolnikova, Nataly ; O'Toole, Timothy E. ; Haas, Thomas A. ; Lam, Stephen C T ; Fox, Joan E B ; Ugarova, Tatiana. / Adhesion-induced unclasping of cytoplasmic tails of integrin α IIbβ 3 In: Biochemistry. 2009 ; Vol. 48, No. 3. pp. 617-629.
@article{0a2bee3d81b54cacb6993d530af88c3f,
title = "Adhesion-induced unclasping of cytoplasmic tails of integrin α IIbβ 3",
abstract = "Integrin α IIbβ 3 plays a pivotal role in hemostasis and thrombosis by mediating adhesive interactions of platelets. Binding of α IIbβ 3 to its physiological ligands, immobilized fibrinogen and fibrin, induces outside-in signaling in platelets, leading to their adhesion and spreading even without prior stimulation by agonists. Implicit in these phenomena is a requirement for the linkage between integrins' cytoplasmic tails and intracellular proteins. However, the nature of the initiating signal has not been established. In this study, we examined whether binding of α IIbβ 3 to immobilized fibrin(ogen), per se, triggers interaction of the integrin with cytoplasmic proteins. Using the integrin-binding skelemin fragment as a marker of exposure of residues involved in the clasp between α IIb and β 3 cytoplasmic tails, we showed that its binding site in the membrane-proximal β 3 715-730 segment is cryptic and becomes exposed as a result of binding of isolated α IIbβ 3 to immobilized ligands. Furthermore, the skelemin-like protein present in platelets and CHO cells does not associate with α IIbβ 3 in resting platelets or suspended α IIbβ 3-expressing CHO cells but is recruited to integrin during cell adhesion. In addition, not only β 3 but also the membrane-proximal 989-1000 segment of the α IIb cytoplasmic tail binds the skelemin fragment. Finally, the same residues, α 3 Val 990, α IIb Arg 995, and β 3 His 722, involved in the formation of the clasp between the tails are also required for skelemin binding. These studies suggest that ligation of α IIbβ 3 by immobilized ligands during platelet adhesion induces a transmembrane conformation change in the integrin, resulting in unclasping of the complex between the membrane-proximal parts of cytoplasmic tails, thereby unmasking residues involved in binding the skelemin-like protein. Thus, the junction between α IIb and β 3 cytoplasmic tails may contain the critical structural information for the initiation of outside-in signaling.",
author = "Nataly Podolnikova and O'Toole, {Timothy E.} and Haas, {Thomas A.} and Lam, {Stephen C T} and Fox, {Joan E B} and Tatiana Ugarova",
year = "2009",
month = "1",
day = "27",
doi = "10.1021/bi801751s",
language = "English (US)",
volume = "48",
pages = "617--629",
journal = "Biochemistry",
issn = "0006-2960",
publisher = "American Chemical Society",
number = "3",

}

TY - JOUR

T1 - Adhesion-induced unclasping of cytoplasmic tails of integrin α IIbβ 3

AU - Podolnikova, Nataly

AU - O'Toole, Timothy E.

AU - Haas, Thomas A.

AU - Lam, Stephen C T

AU - Fox, Joan E B

AU - Ugarova, Tatiana

PY - 2009/1/27

Y1 - 2009/1/27

N2 - Integrin α IIbβ 3 plays a pivotal role in hemostasis and thrombosis by mediating adhesive interactions of platelets. Binding of α IIbβ 3 to its physiological ligands, immobilized fibrinogen and fibrin, induces outside-in signaling in platelets, leading to their adhesion and spreading even without prior stimulation by agonists. Implicit in these phenomena is a requirement for the linkage between integrins' cytoplasmic tails and intracellular proteins. However, the nature of the initiating signal has not been established. In this study, we examined whether binding of α IIbβ 3 to immobilized fibrin(ogen), per se, triggers interaction of the integrin with cytoplasmic proteins. Using the integrin-binding skelemin fragment as a marker of exposure of residues involved in the clasp between α IIb and β 3 cytoplasmic tails, we showed that its binding site in the membrane-proximal β 3 715-730 segment is cryptic and becomes exposed as a result of binding of isolated α IIbβ 3 to immobilized ligands. Furthermore, the skelemin-like protein present in platelets and CHO cells does not associate with α IIbβ 3 in resting platelets or suspended α IIbβ 3-expressing CHO cells but is recruited to integrin during cell adhesion. In addition, not only β 3 but also the membrane-proximal 989-1000 segment of the α IIb cytoplasmic tail binds the skelemin fragment. Finally, the same residues, α 3 Val 990, α IIb Arg 995, and β 3 His 722, involved in the formation of the clasp between the tails are also required for skelemin binding. These studies suggest that ligation of α IIbβ 3 by immobilized ligands during platelet adhesion induces a transmembrane conformation change in the integrin, resulting in unclasping of the complex between the membrane-proximal parts of cytoplasmic tails, thereby unmasking residues involved in binding the skelemin-like protein. Thus, the junction between α IIb and β 3 cytoplasmic tails may contain the critical structural information for the initiation of outside-in signaling.

AB - Integrin α IIbβ 3 plays a pivotal role in hemostasis and thrombosis by mediating adhesive interactions of platelets. Binding of α IIbβ 3 to its physiological ligands, immobilized fibrinogen and fibrin, induces outside-in signaling in platelets, leading to their adhesion and spreading even without prior stimulation by agonists. Implicit in these phenomena is a requirement for the linkage between integrins' cytoplasmic tails and intracellular proteins. However, the nature of the initiating signal has not been established. In this study, we examined whether binding of α IIbβ 3 to immobilized fibrin(ogen), per se, triggers interaction of the integrin with cytoplasmic proteins. Using the integrin-binding skelemin fragment as a marker of exposure of residues involved in the clasp between α IIb and β 3 cytoplasmic tails, we showed that its binding site in the membrane-proximal β 3 715-730 segment is cryptic and becomes exposed as a result of binding of isolated α IIbβ 3 to immobilized ligands. Furthermore, the skelemin-like protein present in platelets and CHO cells does not associate with α IIbβ 3 in resting platelets or suspended α IIbβ 3-expressing CHO cells but is recruited to integrin during cell adhesion. In addition, not only β 3 but also the membrane-proximal 989-1000 segment of the α IIb cytoplasmic tail binds the skelemin fragment. Finally, the same residues, α 3 Val 990, α IIb Arg 995, and β 3 His 722, involved in the formation of the clasp between the tails are also required for skelemin binding. These studies suggest that ligation of α IIbβ 3 by immobilized ligands during platelet adhesion induces a transmembrane conformation change in the integrin, resulting in unclasping of the complex between the membrane-proximal parts of cytoplasmic tails, thereby unmasking residues involved in binding the skelemin-like protein. Thus, the junction between α IIb and β 3 cytoplasmic tails may contain the critical structural information for the initiation of outside-in signaling.

UR - http://www.scopus.com/inward/record.url?scp=59249105293&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=59249105293&partnerID=8YFLogxK

U2 - 10.1021/bi801751s

DO - 10.1021/bi801751s

M3 - Article

C2 - 19117493

AN - SCOPUS:59249105293

VL - 48

SP - 617

EP - 629

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 3

ER -