Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A physical chemical model of T cell stimulation by class I-peptide complexes was developed and used to analyse in vitro studies of gamma-interferon release as a function of the number of peptide and MHC molecules. The analysis provided reasonable estimates of well identified parameters, including equilibrium constants and the minimum number of T cell receptor-class I-peptide ternary complexes on a presenting cell required to activate T cells. The latter number was estimated as 3-5 per T cell. This is in distinct contrast to estimates in the literature of the number of peptide-MHC complexes required for activity, which is necessarily larger. The analysis also predicted that activity is potentiated by interaction between class I molecules, even if one member of the pair is not bound by antigen. The analytical approach used in this paper may be applicable to other activation systems.
Mol Immunol 1994 Nov
PMID:Minimal requirements for peptide mediated activation of CD8+ CTL. 796 89

In this study we analysed the binding of the peptide HEL46-61 to purified Ak molecules which have been altered by site-directed mutagenesis at polymorphic positions to include amino acids from the Ad alpha-chain. We find that changes in the floor of the peptide binding groove, at positions 11, 14 and 28, abolish T cell recognition without changing peptide binding affinity. We further show that amino acid changes at these positions in the Ad molecule result in a conformationally altered molecule as evidenced by loss of binding of the Ad alpha specific monoclonal antibody K24. Thus the T cell receptor is highly sensitive to subtle changes in MHC II structure induced at sites that are unlikely to be involved in direct T cell contact. This has important implications with respect to allorecognition. The binding studies reported here were performed both at pH 7, to reflect binding of peptides at the cell surface, and at pH 5.5, to mimic binding in an intracellular acidic compartment. Binding to wild-type Ak was increased 2-3-fold at pH 5.5, whereas binding to some MHC II mutants was increased by greater than 20-fold at pH 5.5 relative to pH 7. These results show that the apparent peptide binding specificity for the mutants differs at pH 7 and 5.5, and suggest that caution should be used in defining the MHC-restriction of peptide epitopes at neutral pH.
Mol Immunol 1994 Dec
PMID:Effects of MHC II conformation and pH on the recognition of peptide by T cells. 799 42

Staphylococcus enterotoxins and toxic shock syndrome toxin-1 (TSST-1) are members of the family of staphylococcal exoproteins (SE) which binds specifically to HLA class II molecules and certain V beta T cell receptor phenotypes. These bacterial products have been termed "superantigens" due to their capacity to stimulate a greater proportion of T lymphocytes than peptide antigens without a requirement for antigen processing. The SE stimulate monocytes to secrete IL-1 and TNF-alpha and affect B lymphocyte proliferation in response to anti-human IgM and Ig production by PBMC. The current study concerns the transmission of signals in human B lymphocytes following fixation of TSST-1. Activation of both PLC and PKC are observed while intracellular calcium levels remain unchanged. Levels of HLA class II mRNA were increased suggesting that a pathway leading to activation was triggered. This study therefore identifies some of the second messengers involved after SE fixation on HLA class II molecules and suggests that the signals transmitted via class II antigens as well as those via the TCR may have a role in the physiological responses to bacterial superantigens.
Mol Immunol 1994 Jun
PMID:Bacterial superantigen signaling via HLA class II on human B lymphocytes. 802 2

We have constructed antigen-specific chimeric human T cell receptor (TCR) molecules deleted of the transmembrane domain and containing the signal sequence for the biosynthesis of the phosphatidyl inositol glycan (GPI) linkage. These membrane-anchored forms of the TCR alpha and beta chains have been expressed in non-T cells, and they are recognized by alpha or beta TCR specific monoclonal antibodies. We have utilized both immunochemical methods and flow cytometry to prove that the enzyme phosphatidylinositol phospholipase C (PI/PLC) is able to cleave the GPI anchored TCR as a heterodimer from the CHO cell surface. We have demonstrated that the alpha/beta TCR heterodimer on the surface of CHO cells will recognize and bind polymers containing fluorescein (FL-polymer), and the binding activity is completely eliminated by the enzyme, PI/PLC. Moreover, soluble forms of the alpha/beta heterodimer will bind tightly to FL substituted sepharose, which demonstrates the retention of biological activity by the TCR after solubilization. Molecular modelling of the putative antigen binding site of the alpha FL beta FL TCR was derived from the known atomic coordinates of eight different hapten or peptide specific antibodies. Mutagenesis of several residues predicted from the model to be important in FL binding gave results consistent with involvement of Ig equivalent CDR2 and CDR3 domains in the antigen binding pocket. Therefore, using a model hapten system in studying recognition of the TCR independent of MHC interactions, we conclude that amino acid residues located in similar positions within CDR domains as compared to the case of MHC restricted TCR recognition are used in the binding of either hapten or peptide antigens.
Mol Immunol 1994 Aug
PMID:Immunochemical and molecular analysis of antigen binding to lipid anchored and soluble forms of an MHC independent human alpha/beta T cell receptor. 804 75

Two src-family protein tyrosine kinases (PTKs), p56lck, and p59fyn, are thought to play an important role in the antigen-specific T cell receptor (TCR)/CD3-initiated signaling pathway, but their relative contribution to these events is not clearly defined. Here, we have explored the potential of catalytic RNA molecules, or ribozymes, as tools for selectively inhibiting expression of the corresponding target genes in T cells. Several lck- or fyn-specific hammerhead ribozymes were synthesized, cloned into a bacterial transcription vector, and found to display specific catalytic activity in vitro. In order to achieve stable high-level ribozyme expression in intact cells, selected ribozymes were subsequently cloned into a retroviral vector (DC-T5T) immediately downstream of a tRNA(met) transcription unit. Upon retroviral transduction of a human leukemic T cell line (Jurkat), two out of four chimeric tRNA:ribozymes, fyn-1 and lck-1, were stably expressed at levels of approximately 10,000 or approximately 25,000 copies/cell, respectively. Ribozyme expression was associated with a reduction of up to 80% (lck) or 61% (fyn) in endogenous target mRNA by comparison to the corresponding transcript levels in control clones transfected with vector alone. By contrast, expression of the corresponding target proteins was not reduced, suggesting a post-transcriptional compensatory mechanism that increases translation or stability of the p56lck and/or p59fyn proteins.
Mol Immunol 1994 Aug
PMID:Construction and characterization of lck- and fyn-specific tRNA: ribozyme chimeras. 806 75

The alloreactive CD8+ cytotoxic T lymphocyte (CTL) clone 2C was previously shown to recognize complexes made up of the class I MHC (MHC-I) molecule Ld and an octapeptide (LSPFPFDL, termed p2Ca) isolated from tissues of H-2d mice. Because peptide p2Ca has also been found in BALB.B (H-2b) mice, the strain from which clone 2C originated, the question arises as to whether these T cells can recognize peptide p2Ca in association with a self MHC protein of the H-2b haplotype. Here we show that 2C CTL do indeed recognize peptide p2Ca in association with Kb on the surface of H-2b cells or on transfected cells expressing Kb, but that an approximately 1000-fold higher concentration of this peptide is required to sensitize Kb+ than Ld+ target cells for lysis by 2C cells. However, the peptide's binding to Kb was not much weaker than to Ld, with only an approximately 10-fold difference in the respective equilibrium constants. These results predict that the T cell receptor (TcR) of clone 2C has a much lower intrinsic affinity for p2Ca-Kb complexes than for p2Ca-Ld complexes, and they provide some quantitative limits on the requirements for triggering T cell-mediated autoimmune reactivity.
Mol Immunol 1994 Sep
PMID:A cytotoxic T lymphocyte clone can recognize the same naturally occurring self peptide in association with a self and nonself class I MHC protein. 808 37

We recently reported the expression of a truncated T cell receptor (TCR) alpha mRNA in kidney and brain of normal mice. In the kidney, the truncated TCR alpha transcript was expressed by bone marrow-dependent, non-T large interstitial cells located predominantly in the medulla. Here, we report the molecular characterization of the truncated TCR alpha transcript from kidney. Using a modified anchored-PCR (A-PCR) technique and directional cloning, 37 cDNA clones extending 5' of the C alpha region were generated. cDNA sequencing showed that 29 of the clones (78%) originated in the J alpha 11-2 region. Of these clones, 17 started upstream or in the J alpha 11-2 exon and contained the entire J alpha 11-2 sequence correctly spliced to the first C alpha exon. Analysis of the sequence revealed the presence of multiple stop codons in all three reading frames. The other 12 clones originated further upstream of the J alpha 11-2 exon and did not include the J alpha 11-2 exon, but rather arose from the joining of a cryptic splice donor signal to the usual TCR alpha C splice acceptor. This alternatively spliced transcript contained an open reading frame extending from the upstream J alpha 11-2 region to 82 nucleotides downstream of the beginning of the TCR C alpha region, and potentially encoded a 36 amino acid polypeptide. The remaining eight clones all contained the J alpha TA61 region correctly spliced to C alpha with two of these extending upstream of the J alpha TA61 exon. The predominance of J alpha 11-2-C alpha containing clones was confirmed by RNase protection assay using total RNA from kidney and spleen of scid mice. The 3' region of the transcript contained a fully conserved, correctly spliced TCR alpha C region which was polyadenylated at the 3' end. The truncated TCR alpha mRNA could be detected in preparations of cytoplasmic RNA, indicating that this transcript follows a normal RNA processing pathway. Our results demonstrate that the truncated TCR alpha mRNA expressed in normal mouse kidney is a germline J-C transcript resulting from transcription initiated predominantly upstream of the J alpha 11-2 region. This germline transcript in the kidney is undergoing alternative splicing leading to the appearance of an open reading frame coding for a short polypeptide. These results suggest that the product of this transcript may be functionally relevant.
Mol Immunol 1994 Sep
PMID:Alternatively spliced, germline J alpha 11-2-C alpha mRNAs are the predominant T cell receptor alpha transcripts in mouse kidney. 808 39

The cytoplasmic segment of the CD8 alpha polypeptide includes both a cysteine-containing motif that is required for its association with the tyrosine kinase p56lck, and two serine residues which are likely to be phosphorylated and involved in inside-out signaling phenomena. To determine the relative importance of these residues for CD8 function, a mouse T cell hybridoma expressing a T cell receptor specific for the class I major histocompatibility product H-2Kb was transfected with a set of CD8 alpha chain genes encoding polypeptides in which the cytoplasmic cysteine or serine residues were substituted with alanine. When challenged with Kb-transfected L cells, T cell transfectants expressing CD8 alpha beta or CD8 alpha alpha dimers with substituted cytoplasmic serine residues responded nearly as well as wild-type CD8 transfectants. In marked contrast, the CD8 alpha polypeptides bearing substitutions of both cytoplasmic cysteine residues were totally impaired in their ability to complement the co-expressed T cell receptor.
Mol Immunol 1993 Jun
PMID:The cysteine residues in the cytoplasmic tail of CD8 alpha are required for its coreceptor function. 809 95

Ganglioside (GM1) modulation of CD4 off the surface of T lymphocytes defined functions of the CD4 molecule during signal transduction through the T cell receptor (TCR)/CD3 complex. Antibody cross-linking of CD3 alone (3 x 3) stimulated phospholipase C (PLC) activity, rapid Ca2+ flux, and protein phosphorylations in freshly isolated human T lymphocytes. Antibody cross-linking of CD4 and CD3 (3 x 4) stimulated greater signaling than that caused by 3 x 3. Cross-linking CD4 alone did not stimulate these signaling processes. GM1-modulation of CD4 from the cell surface blocked all aspects of the augmented signaling imparted by CD4 co-modulation with CD3. In comparison, pretreatment with the protein tyrosine kinase inhibitor genistein inhibited 3 x 4-stimulated PLC activity and protein phosphorylation but not Ca2+ flux. Antibody cross-linking of the tyrosine phosphatase CD45 with 3 x 4 (3 x 4 x 45) also inhibited CD4-augmented phosphorylations and like genistein did not reduce Ca2+ levels. In conclusion, these data demonstrate that CD4 can augment signal transduction through the TCR/CD3 complex by its physical proximity to CD3. TCR/CD3-signaling augmentation by CD4 stimulated protein tyrosine kinases and PLC activities but stimulated intracellular Ca2+ flux through an independent mechanism(s).
Cell Mol Biol Res 1993
PMID:Ganglioside (GM1) distinguishes the effects of CD4 on signal transduction through the TCR/CD3 complex in human lymphocytes. 810 89

Positive and negative transcriptional regulatory mechanisms are thought to play a major role in the expression of T cell antigen receptor (TCR) genes. Since the alpha beta and gamma delta T cell receptor heterodimers are expressed in a mutually exclusive fashion and since TCR genes are sequentially activated during T cell ontogeny, transcriptional activation and repression must at least in part determine T lineage-specific and developmental-specific expression of these genes. We have identified a transcriptional enhancer located 6.5 kb downstream from the human T cell receptor gamma (TRG) locus. The nucleotide sequence of the enhancer core element shows strong sequence homology to the recently identified murine C gamma 1 enhancer. The enhancer demonstrates T cell-specific activity, but not gamma delta sublineage-specificity in combination with either a heterologous or gene-specific promoter. Thus, additional regulatory elements may be required to repress the expression of rearranged TRG genes in non-gamma delta T cells.
Mol Immunol 1994 Mar
PMID:Identification of a T cell-specific transcriptional enhancer 3' of the human T cell receptor gamma locus. 813 85


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>