title: Critical cysteine residues for regulation of integrin alphaIIbbeta3 are clustered in the epidermal growth factor domains of the beta3 subunit.
abstract: Chemical or enzymic reduction/oxidation of integrin cysteine residues (e.g. by reducing agents and protein disulphide isomerase) may be a mechanism for regulating integrin function. It has also been proposed that unique cysteine residues in the integrin beta3 subunit are involved in the regulation of alphaIIbbeta3. In the present study, we studied systematically the role of disulphide bonds in beta3 on the ligand-binding function of alphaIIbbeta3 by mutating individual cysteine residues of beta3 to serine. We found that the disulphide bonds that are critical for alphaIIbbeta3 regulation are clustered within the EGF (epidermal growth factor) domains. Interestingly, disrupting only a single disulphide bond in the EGF domains was enough to activate alphaIIbbeta3 fully. In contrast, only two (of 13) disulphide bonds tested outside the EGF domains activated alphaIIbbeta3. These results suggest that the disulphide bonds in the EGF domains should be intact to keep alphaIIbbeta3 in an inactive state, and that there is no unique cysteine residue in the EGF domain critical for regulating the receptor. The cysteine residues in the EGF domains are potential targets for chemical or enzymic reduction.
authors.affiliation: Department of Cell Biology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Kamata
authors.forename: Hironobu
authors.initials: H
authors.lastname: Ambo
authors.forename: Wilma
authors.initials: W
authors.lastname: Puzon-McLaughlin
authors.forename: Kenneth Khiem
authors.initials: KK
authors.lastname: Tieu
authors.forename: Makoto
authors.initials: M
authors.lastname: Handa
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ikeda
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Takada
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003545:Cysteine / Q000235:genetics / Q000502:physiology*; D004220:Disulfides / Q000737:chemistry; D004815:Epidermal Growth Factor / Q000737:chemistry*; D005340:Fibrinogen / Q000378:metabolism; D006801:Humans; D039661:Integrin beta3 / Q000737:chemistry* / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000737:chemistry* / Q000378:metabolism*; D017434:Protein Structure, Tertiary
chemical_list: D004220:Disulfides; D039661:Integrin beta3; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D004815:Epidermal Growth Factor; D005340:Fibrinogen; D003545:Cysteine