Studies of Fc(gamma)R signalling: I.~A chimeric HSA-muFc(gamma)RIIb2 receptor. II.~huFc(gamma)RIIA: Induced tyrosine phosphorylation.
Item
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Title
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Studies of Fc(gamma)R signalling: I.~A chimeric HSA-muFc(gamma)RIIb2 receptor. II.~huFc(gamma)RIIA: Induced tyrosine phosphorylation.
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Identifier
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AAI9405570
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identifier
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9405570
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Creator
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Painter, Catherine Jean.
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Contributor
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Adviser: Jay C. Unkeless
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Date
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1993
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Biochemistry | Biology, Cell | Health Sciences, Immunology
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Abstract
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Fc receptors for IgG bind IgG via the Fc domain, linking humoral and cellular immunity. Elucidation of signalling pathways has been exciting, with the recent realization that several immune receptors share a common tyrosine activation motif. This motif is necessary and sufficient for T cell receptor signalling.;Study of a chimeric HSA-muFc{dollar}\sb{lcub}\rm gamma{rcub}{dollar}RIIb2 receptor expressed in the P388D1 cell line revealed that the extracellular domain of the muFc{dollar}\sb{lcub}\rm gamma{rcub}{dollar}RIIb2 receptor is not required for signalling for phagocytosis of immune complexes. Thus, crosslinking of Fc{dollar}\sb{lcub}\rm gamma{rcub}{dollar}Rs, in the absence of any conformational change in the extracellular domain, is sufficient to initiate signalling.;Activation of huFc{dollar}\sb{lcub}\rm gamma{rcub}{dollar}RIIA led to rapid tyrosine phosphorylation and dephosphorylation of distinct cellular proteins. Herbimycin A pretreatment demonstrated that the tyrosine phosphorylation response is required for {dollar}\rm \lbrack Ca\sp{lcub}2+{rcub}\rbrack \sb{lcub}i{rcub}{dollar} flux and phagocytosis. Severe truncations of the cytoplasmic domain abolished all functioning. The {dollar}\Delta{dollar}264 receptor, missing 17 carboxyl--terminal amino acids including the downstream YXXL of the motif, is capable of a partial tyrosine phosphorylation response. The subset of tyrosine phosphorylation preserved in {dollar}\Delta{dollar}264 may be involved in phagocytosis of immune complexes mediated by this receptor, but is not sufficient for the {dollar}\rm \lbrack Ca\sp{lcub}2+{rcub}\rbrack \sb{lcub}i{rcub}{dollar} flux abrogated by this deletion.;While nine of ten various point mutants were phenotypically wildtype, mutation of the tyrosine of the upstream YXXL dyad to phenylalanine (Y252F) resulted in a significantly crippled receptor, incapable of {dollar}\rm \lbrack Ca\sp{lcub}2+{rcub}\rbrack \sb{lcub}i{rcub}{dollar} flux or phagocytosis. The tyrosine phosphorylation response of Y252F, while diminished in intensity, was largely intact, with a major exception of a 51,000 Da protein. The absence of tyrosine phosphorylated p51 from the response of both {dollar}\Delta{dollar}264 and Y252F, which are both incapable of {dollar}\rm \lbrack Ca\sp{lcub}2+{rcub}\rbrack \sb{lcub}i{rcub}{dollar} flux, suggests that p51 is an early and important constituent of the signalling pathway of huFc{dollar}\sb{lcub}\rm gamma{rcub}{dollar}RIIA. The phosphorylation response of Y252F was delayed but dephosphorylation was significantly delayed, suggesting that protein tyrosine phosphatases involved in the signalling cascade are not constitutively active but are induced upon receptor engagement.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
