Signal transduction and structure function studies of human Fc(gamma)RIIA.
Item
-
Title
-
Signal transduction and structure function studies of human Fc(gamma)RIIA.
-
Identifier
-
AAI9432351
-
identifier
-
9432351
-
Creator
-
Lin, Ching-Tai.
-
Contributor
-
Adviser: Jay Unkeless
-
Date
-
1994
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Health Sciences, Immunology | Biology, Cell | Biology, Molecular
-
Abstract
-
Receptors for the Fc domain of IgG (Fc{dollar}\sb\gamma{dollar}R) on leukocytes mediate a pleiotropic response following crosslinking by immune complexes. Signaling events mediated by crosslinking of human Fc{dollar}\sb\gamma{dollar}RIIA and Fc{dollar}\sb\gamma{dollar}RIIA mutants were analyzed in transfected P388D{dollar}\sb1{dollar} mouse macrophage cell lines. Activation of wild type Fc{dollar}\sb\gamma{dollar}RIIA in transfected P388D{dollar}\sb1{dollar} cells led to rapid and transitory tyrosine-phosphorylation of several proteins, including the tyrosine kinase p72{dollar}\sp{lcub}\rm syk{rcub}.{dollar} We analyzed mutants in both Y-X-X-L motifs of the Fc{dollar}\sb\gamma{dollar}RIIA cytoplasmic domain. Deletion of the COOH-terminal motif, mutation of Tyr{dollar}\sp{lcub}268{rcub}{dollar} to Phe, Leu, or Ser, and mutation of Leu{dollar}\sp{lcub}271{rcub}{dollar} to Ala resulted in Fc{dollar}\sb\gamma{dollar}R's that did not activate p72{dollar}\sp{lcub}\rm syk{rcub}{dollar}, flux {dollar}\lbrack\rm Ca\sp{lcub}2+{rcub}\rbrack\sb{lcub}i{rcub},{dollar} or phagocytose IgG sensitized erythrocytes, but which were competent to internalize immune complexes and to phosphorylate on tyrosine a subset of the normal substrates. Mutation of the NH{dollar}\sb3{dollar}-terminal motif was more complicated. Mutation of Tyr{dollar}\sp{lcub}252{rcub}{dollar} to Ser or Leu did not alter the phenotype. However, mutation of Tyr{dollar}\sp{lcub}252{rcub}{dollar} to Phe, or Leu{dollar}\sp{lcub}255{rcub}{dollar} to Glu resulted in a severely impaired phenotype, unable to flux {dollar} \lbrack\rm Ca\sp{lcub}2+{rcub}\rbrack\sb{lcub}i{rcub},{dollar} lacking most (but not all) tyrosine kinase activity, and capable of internalizing complexes only after extensive crosslinking. In contrast, deletion of both motifs resulted in a completely inactive receptor, unable to activate tyrosine kinases, to flux {dollar}\lbrack\rm Ca\sp{lcub}2+{rcub}\rbrack\sb{lcub}i{rcub},{dollar} or to internalize complexes.;Crosslinking Fc{dollar}\sb\gamma{dollar}RIIA led to the transient generation of inositol trisphosphate, {dollar}\lbrack\rm Ca\sp{lcub}2+{rcub}\rbrack\sb{lcub}i{rcub}{dollar} flux, and rapid tyrosine phosphorylation of cellular substrates, including Shc, PLC-{dollar}\sb\gamma{dollar}1, and a tyrosine kinase p72{dollar}\sp{lcub}\rm syk{rcub}.{dollar} In contrast, no tyrosine phosphorylation of Shc or PLC-{dollar}\sb\gamma{dollar}1 was detected in cells transfected with mutant receptors that failed to trigger {dollar}\lbrack\rm Ca\sp{lcub}2+{rcub}\rbrack\sb{lcub}i{rcub}{dollar} flux. PMA inhibits both tyrosine phosphorylation of Shc and IP3 production leading to {dollar} \lbrack\rm Ca\sp{lcub}2+{rcub}\rbrack\sb{lcub}i{rcub}{dollar} flux. However, PMA does not affect tyrosine phosphorylation of PLC-{dollar}\sb\gamma{dollar}1 and p72{dollar}\sp{lcub}\rm syk{rcub}.{dollar} These results suggest that tyrosine phosphorylation of Shc and PLC-{dollar}\sb\gamma{dollar}1 is important for the initiation of {dollar}\lbrack\rm Ca\sp{lcub}2+{rcub}\rbrack\sb{lcub}i{rcub}{dollar} flux, and that activation of protein kinase C (PKC) may modulate the activity of PLC-{dollar}\sb\gamma{dollar}1.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
