TY - JOUR
T1 - Critical roles for the COOH-terminal NITY and RGT sequences of the integrin β3 cytoplasmic domain in inside-out and outside-in signaling
AU - Xi, Xiaodong
AU - Bodnar, Richard J.
AU - Li, Zhenyu
AU - Lam, Stephen C.T.
AU - Du, Xiaoping
PY - 2003/7/21
Y1 - 2003/7/21
N2 - Bidirectional signaling of integrin αIIbβ3 requires the β3 cytoplasmic domain. To determine the sequence in the β3 cytoplasmic domain that is critical to integrin signaling, cell lines were established that coexpress the platelet receptor for von Willebrand factor (vWF), glycoprotein Ib-IX, integrin αIIb, and mutants of β3 with truncations at sites COOH terminal to T741, Y747, F754, and Y759. Truncation at Y759 did not affect integrin activation, as indicated by vWF-induced fibrinogen binding, but affected cell spreading and stable adhesion. Thus, the COOH-terminal RGT sequence of β3 is important for outside-in signaling but not inside-out signaling. In contrast, truncation at F754, Y747, or T741 completely abolished integrin activation. A point mutation replacing Y759 with alanine also abolished integrin activation. Thus, the T755NITY759 sequence of β3, containing an NXXY motif, is critical to inside-out signaling, whereas the intact COOH terminus is important for outside-in signaling. In addition, we found that the calcium-dependent protease calpain preferentially cleaves at Y759 in a population of β3 during platelet aggregation and adhesion, suggesting that calpain may selectively regulate integrin outside-in signaling.
AB - Bidirectional signaling of integrin αIIbβ3 requires the β3 cytoplasmic domain. To determine the sequence in the β3 cytoplasmic domain that is critical to integrin signaling, cell lines were established that coexpress the platelet receptor for von Willebrand factor (vWF), glycoprotein Ib-IX, integrin αIIb, and mutants of β3 with truncations at sites COOH terminal to T741, Y747, F754, and Y759. Truncation at Y759 did not affect integrin activation, as indicated by vWF-induced fibrinogen binding, but affected cell spreading and stable adhesion. Thus, the COOH-terminal RGT sequence of β3 is important for outside-in signaling but not inside-out signaling. In contrast, truncation at F754, Y747, or T741 completely abolished integrin activation. A point mutation replacing Y759 with alanine also abolished integrin activation. Thus, the T755NITY759 sequence of β3, containing an NXXY motif, is critical to inside-out signaling, whereas the intact COOH terminus is important for outside-in signaling. In addition, we found that the calcium-dependent protease calpain preferentially cleaves at Y759 in a population of β3 during platelet aggregation and adhesion, suggesting that calpain may selectively regulate integrin outside-in signaling.
KW - Calpain
KW - Integrin
KW - Platelet
KW - Platelet activation
KW - Signaling
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UR - http://www.scopus.com/inward/citedby.url?scp=0042672885&partnerID=8YFLogxK
U2 - 10.1083/jcb.200303120
DO - 10.1083/jcb.200303120
M3 - Article
C2 - 12860973
AN - SCOPUS:0042672885
SN - 0021-9525
VL - 162
SP - 329
EP - 339
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 2
ER -