Abstract
Adapter proteins link catalytic signaling proteins to cell surface receptors or downstream effector proteins. In this paper, we present the cDNA sequence F2771, isolated from an activated CD8+ T cell cDNA library. The F2771 cDNA encodes a novel putative adapter protein. The predicted amino acid sequence includes an SH2 domain as well as putative SH3 and phosphotyrosine binding interaction motifs, but lacks any known catalytic domains. The expression of the gene is limited to tissues of the immune system and, in particular, activated T cells. The protein expressed by F2771 cDNA in transfected COS cells is localized in the cytoplasm. A polyclonal antiserum raised against an F2771-encoded peptide reacts with a tyrosine-phosphorylated 52-kDa protein expressed in phytohemagglutinin-stimulated peripheral blood mononuclear cells. The gene is localized to chromosome 1q21, a region often found to be aberrant in lymphomas. The T cell-specific expression and the rapid induction of mRNA expression upon receptor binding, as well as the lack of catalytic domains in the presence of protein interaction domains, indicate that the F2771 gene encodes a novel T cell-specific adapter protein (TSAd) involved in the control of T cell activation.
Highlights
Activation of T cells involves interaction of the T cell antigen receptor (TCR)1 with complexes of peptides and major histocompatibility complex class I or II molecules
The gene continues to be expressed in long term cultures of activated T cells. We propose that this protein, due to the presence of an Src homology 2 (SH2) domain and putative Src homology 3 (SH3) and phosphotyrosine binding (PTB) binding motifs, is an adapter molecule involved in proteinprotein interactions during T cell activation
Initial Northern blot analysis showed that the F2771 cDNA hybridized to a single band of approximately 1700 bp, expressed in activated CD8ϩ cells and not in the Jurkat cell line used as subtractor, confirming the efficiency of the subtraction
Summary
Activation of T cells involves interaction of the T cell antigen receptor (TCR) with complexes of peptides and major histocompatibility complex class I or II molecules. We initiated experiments to identify genes that are expressed in activated CD8ϩ T cells using a subtractive strategy. The gene continues to be expressed in long term cultures of activated T cells We propose that this protein, due to the presence of an SH2 domain and putative SH3 and PTB binding motifs, is an adapter molecule involved in proteinprotein interactions during T cell activation. This novel protein may be termed TSAd, for T cell SH2 domain-containing adapter protein
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