Cloning and characterization of human Lnk, an adaptor protein with pleckstrin homology and Src homology 2 domains that can inhibit T cell activation.
Lnk was originally cloned from a rat lymph node cDNA library and shown to participate in T cell signaling. Human Lnk (hLnk) was cloned by screening a Jurkat cell cDNA library. hLnk has a calculated molecular mass of 63 kDa, and its deduced amino acid sequence indicates the presence of an N-terminal proline-rich region, a pleckstrin homology domain, and a Src homology 2 domain. When expressed in COS cells, hLnk migrates with an apparent molecular mass of 75 kDa. Confocal fluorescence microscope analysis indicates that in COS cells transfected with an expression vector encoding a chimeric Lnk-green fluorescent protein, hLnk is found at the juxtanuclear compartment and also appears to be localized at the plasma membrane. Lnk is tyrosine-phosphorylated by p56lck. Following phosphorylation, p56lck binds to tyrosine-phosphorylated hLnk through its Src homology 2 domain. In COS cells cotransfected with hLnk, p56lck, and CD8-zeta, hLnk associated with tyrosine-phosphorylated TCR zeta-chain through its Src homology 2 domain. The overexpression of Lnk in Jurkat cells led to an inhibition of anti-CD3 mediated NF-AT-Luc activation. Our study reveals a potentially new mechanism of T cell-negative regulation.
Li
Y
Y
School of Pharmacy, University of Maryland, Baltimore, MD 21201, USA.
He
X
X
Schembri-King
J
J
Jakes
S
S
Hayashi
J
J
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000818:Animals; D001798:Blood Proteins / Q000737:chemistry*; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry; D018076:DNA, Complementary / Q000302:isolation & purification; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors; D004792:Enzyme Precursors / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000276:immunology*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D008969:Molecular Sequence Data; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010750:Phosphoproteins / Q000737:chemistry*; D010766:Phosphorylation; D011485:Protein Binding / Q000276:immunology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011948:Receptors, Antigen, T-Cell / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000276:immunology; D000072377:Syk Kinase; D013601:T-Lymphocytes / Q000276:immunology*; D014157:Transcription Factors / Q000037:antagonists & inhibitors; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains / Q000276:immunology*
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D001798:Blood Proteins; D002352:Carrier Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; C490777:Lnk protein, mouse; D008565:Membrane Proteins; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011506:Proteins; D012333:RNA, Messenger; D011948:Receptors, Antigen, T-Cell; C518910:SH2B1 protein, human; C492010:SH2B1 protein, rat; C107249:SH2B2 protein, human; C490778:SH2B3 protein, human; C488161:Sh2b2 protein, mouse; C488162:Sh2b2 protein, rat; C097176:Sh2b3 protein, rat; D014157:Transcription Factors; C054979:antigen T cell receptor, zeta chain; C039077:platelet protein P47; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; C000606898:Syk protein, rat