CD3 gamma contains a phosphoserine-dependent di-leucine motif involved in down-regulation of the T cell receptor

Research output: Contribution to journalJournal articleResearchpeer-review

Several cell surface receptors including the T cell receptor (TCR) are phosphorylated and down-regulated following activation of protein kinase C (PKC). Among other substrates the activated PKC in T cells phosphorylates the CD3 gamma subunit of the TCR. To investigate the role of CD3 gamma phosphorylation in PKC-mediated TCR down-regulation, point mutated CD3 gamma cDNA was transfected into the CD3 gamma-negative T cell line JGN and CD3 gamma transfectants were analysed. Phosphorylation at S126 but not S123 in the cytoplasmic tail of CD3 gamma was required for PKC-mediated down-regulation of the TCR. Furthermore, analysis of a series of CD3 gamma truncation mutants indicated that in addition to S126 phosphorylation a motif C-terminal of S126 was required for TCR down-regulation. Point mutation analyses confirmed this observation and demonstrated that a membrane-proximal di-leucine motif (L131 and L132) in the cytoplasmic tail of CD3 gamma was required for PKC-mediated TCR down-regulation in addition to phosphorylation at S126. Incubation of T cells in hypertonic medium known to disrupt normal clathrin lattices severely inhibited PKC-mediated TCR down-regulation in non-mutated T cells, indicating that the TCR was down-regulated by endocytosis via clathrin coated pits. Based on the present results and previously published observations on intracellular receptor sorting, a general model for intracellular sorting of receptors containing di-leucine- or tyrosine-based motifs is proposed.
Original languageEnglish
JournalEMBO Journal
Issue number9
Pages (from-to)2156-66
Number of pages10
Publication statusPublished - 1994

Bibliographical note

Keywords: Amino Acid Sequence; Antigens, CD3; Cell Line; Coated Pits, Cell-Membrane; Down-Regulation; Endocytosis; Enzyme Activation; Humans; Leucine; Molecular Sequence Data; Phosphorylation; Phosphoserine; Point Mutation; Protein Kinase C; Receptors, Antigen, T-Cell; T-Lymphocytes; Transfection; Tyrosine

ID: 8545944