title: Phosphatase CD45 both positively and negatively regulates T cell receptor phosphorylation in reconstituted membrane protein clusters.
abstract: T cell receptor (TCR) phosphorylation requires the kinase Lck and phosphatase CD45. CD45 activates Lck by dephosphorylating an inhibitory tyrosine of Lck to relieve autoinhibition. However, CD45 also dephosphorylates the TCR, and the spatial exclusion of CD45 from TCR clustering in the plasma membrane appears to attenuate this negative effect of CD45. To further investigate the role of CD45 in signal initiation, we reconstituted membrane TCR clusters in vitro on supported lipid bilayers. Fluorescence microscopy of single clusters showed that incorporation of CD45 enhanced phosphorylation of TCR clusters, but only when Lck co-clustered with TCR. We found that clustered Lck autophosphorylated the inhibitory tyrosine and thus could be activated by CD45, whereas diffusive Lck molecules did not. In the TCR-Lck clusters and at low CD45 density, we speculate that the effect of Lck activation may overcome dephosphorylation of TCR, resulting in a net positive regulation. The CD45 density in physiological TCR clusters is also low because of the exclusion of CD45. Thus, we propose that the spatial organization of TCR/Lck/CD45 in T cell membranes is important not only for modulating the negative role of CD45 but also for creating conditions in which CD45 has a positive role in signal initiation.
authors.affiliation: From the International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Furlan
authors.affiliation: From the International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Minowa
authors.affiliation: From the International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Hanagata
authors.affiliation: From the International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Chiho
authors.initials: C
authors.lastname: Kataoka-Hamai
authors.affiliation: From the International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan KAIZUKA.Yoshihisa@nims.go.jp.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kaizuka
mesh_terms: D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D017493:Leukocyte Common Antigens / Q000235:genetics / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics / Q000378:metabolism*; D057054:Molecular Imaging; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism; D010718:Phosphatidylserines / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D061987:Sf9 Cells; D015398:Signal Transduction; D018411:Spodoptera; D051844:alpha-Synuclein / Q000235:genetics / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D011948:Receptors, Antigen, T-Cell; D011994:Recombinant Proteins; D051844:alpha-Synuclein; D049452:Green Fluorescent Proteins; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D017493:Leukocyte Common Antigens; C516769:PTPRC protein, human; C017251:1,2-oleoylphosphatidylcholine
keywords: Signal Transduction; Src; Supported Lipid Bilayers; T Cell Receptor (TCR); Tyrosine-Protein Kinase (Tyrosine Kinase); Tyrosine-Protein Phosphatase (Tyrosine Phosphatase)