Structure of an integrin alphaIIb beta3 transmembrane-cytoplasmic heterocomplex provides insight into integrin activation.
Heterodimeric integrin adhesion receptors regulate diverse biological processes including angiogenesis, thrombosis and wound healing. The transmembrane-cytoplasmic domains (TMCDs) of integrins play a critical role in controlling activation of these receptors via an inside-out signaling mechanism, but the precise structural basis remains elusive. Here, we present the solution structure of integrin alphaIIb beta3 TMCD heterodimer, which reveals a right-handed coiled-coil conformation with 2 helices intertwined throughout the transmembrane region. The helices extend into the cytoplasm and form a clasp that differs significantly from a recently published alphaIIb beta3 TMCD structure. We show that while a point mutation in the clasp interface modestly activates alphaIIb beta3, additional mutations in the transmembrane interface have a synergistic effect, leading to extensive integrin activation. Detailed analyses and structural comparison with previous studies suggest that extensive integrin activation is a highly concerted conformational transition process, which involves transmembrane coiled-coil unwinding that is triggered by the membrane-mediated alteration and disengagement of the membrane-proximal clasp. Our results provide atomic insight into a type I transmembrane receptor heterocomplex and the mechanism of integrin inside-out transmembrane signaling.
Yang
Jun
J
Department of Molecular Cardiology NB20, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Ma
Yan-Qing
YQ
Page
Richard C
RC
Misra
Saurav
S
Plow
Edward F
EF
Qin
Jun
J
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D003593:Cytoplasm / Q000378:metabolism; D019281:Dimerization; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D016297:Mutagenesis, Site-Directed; D019906:Nuclear Magnetic Resonance, Biomolecular; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection
D046912:Multiprotein Complexes; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011994:Recombinant Proteins