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E Appella

Publications and source records attributed to E Appella.

At least 19 recordsLinked to original sources
PubMed1996

The oligomerization domain of p53: crystal structure of the trigonal form.

The structure of the oligomerization domain of the p53 tumor suppressor protein was determined in the trigonal crystal form, using a refined NMR structure as a model. A synthetic peptide comprising residues 319-360 of human p53 crystallized in the space group P3(1)21. There is one biologically relevant tetrameric domain in the crystallographic asymmetric unit. The structure was refined jointly with NMR data, only the third such case (the previous examples being IL-1beta (Shaanan, B., Gronenborn, A.M., Cohen, G.H., Gilliland, G.L., Veerapandian, B., Davies, D.R. and Clore, G.M. (1992) Science 257, 961-964 [1]) and BPTI (Schiffer, C., Huber, R., Wuthrich, K. and Van Gunsteren, W.F. (1994) J. Mol. Biol. 241, 588-599 [21)), to 2.5 A resolution with an R factor of 0.207. The distribution of tumor-derived mutations in the oligomerization region together with structural and biological data suggest a strategy for the design of antitumor therapeutics.

Biopolymers↗
PubMed1996

Identification of TRP-2 as a human tumor antigen recognized by cytotoxic T lymphocytes.

The infusion of TIL586 along with interleukin-2 into the autologous patient with metastatic melanoma resulted in the objective regression of tumor. A gene encoding a tumor antigen recognized by TIL586 was previously isolated and shown to encode gp75 or TRP-1. Here we report that TRP-2 was identified as a second tumor antigen recognized by a HLA-A31-restricted CTL clone derived from the TIL586 cell line. The peptide LLPGGRPYR epitope was subsequently identified from the coding region of TRP-2 based on studies of the recognition of truncated TRP-2 cDNAs and the HLA-A31 binding motif. This epitope peptide was capable of sensitizing target cells for lysis by a CTL clone at 1 nM peptide concentration. Although some modified peptides could be recognized by the CTL clone, none were found to be better recognized by T cells than the parental peptide. Like other melamona differentiation antigens, TRP-2 was only expressed in melanoma, melanocytes, and retina, but not in other human tissues tested.

Amino Acid Sequence↗
PubMed1996

Downstream signaling molecules bind to different phosphorylated immunoreceptor tyrosine-based activation motif (ITAM) peptides of the high affinity IgE receptor.

The cytoplasmic tails of both the beta and gamma subunits of the high affinity IgE receptor (FcepsilonRI) contain a consensus sequence termed the immunoreceptor tyrosine-based activation motif (ITAM). This motif plays a critical role in receptor-mediated signal transduction. Synthetic peptides based on the ITAM sequences of the beta and gamma subunits of FcepsilonRI were used to investigate which proteins associate with these motifs. Tyrosine-phosphorylated beta and gamma ITAM peptides immobilized on beads precipitated Syk, Lyn, Shc, Grb2, and phospholipase C-gamma1 from lysates of rat basophilic leukemia RBL-2H3 cells. Syk was precipitated predominantly by the tyrosine-diphosphorylated gamma ITAM peptide, but much less by the diphosphorylated beta ITAM peptide or by the monophosphorylated peptides. Phospholipase C-gamma1, Shc, and Grb2 were precipitated only by the diphosphorylated beta ITAM peptide. Non-phosphorylated ITAM peptides did not precipitate these proteins. In membrane binding assays, fusion proteins containing the Src homology 2 domains of phospholipase C-gamma1, Shc, Syk, and Lyn directly bound the tyrosine-phosphorylated ITAM peptides. Although the ITAM sequences of the beta and gamma subunits of FcepsilonRI are similar, once they are tyrosine-phosphorylated they preferentially bind different downstream signaling molecules. Tyrosine phosphorylation of the ITAM of the gamma subunit recruits and activates Syk, whereas the beta subunit may be important for the Ras signaling pathway.

Amino Acid Sequence↗
PubMed1996

Invariant chain and DM edit self-peptide presentation by major histocompatibility complex (MHC) class II molecules.

We have studied the consequences of invariant chain (Ii) and DM expression on major histocompatibility complex (MHC) class II function. Ii has a number of discrete functions in the biology of class II, including competitive blocking of peptide binding in the endoplasmic reticulum and enhancing localization in the endocytic compartments. DM is thought to act primarily in endosomes to promote dissociation of the Ii-derived (CLIP) peptide from the class II antigen-binding pocket and subsequent peptide loading. In this study, we have evaluated the functional role of Ii and DM by examining their impact on surface expression of epitopes recognized by a large panel of alloreactive T cells. We find most epitopes studied are influenced by both Ii and DM. Most strikingly, we find that surface expression of a significant fraction of peptide-class II complexes is extinguished, rather than enhanced, by DM expression within the APC. The epitopes antagonized by DM do not appear to be specific for CLIP. Finally, we found that DM was also able to extinguish recognition of a defined peptide derived from the internally synthesized H-2Ld protein. Thus, rather than primarily serving in the removal of CLIP, DM may have a more generalized function of editing the array of peptides that are presented by class II. This editing can be either positive or negative, suggesting that DM plays a specifying role in the display of peptides presented to CD4 T cells.

Animals↗
PubMed1996

The proteolytic environment involved in MHC class II-restricted antigen presentation can be modulated by the p41 form of invariant chain.

During biosynthesis, MHC class II associates with invariant chain which exists in two forms, p31 and p41. Both forms of invariant chain prevent peptide binding to class II, facilitate transport, and enhance class II localization to Ag-processing compartments. In spite of these shared functions, presentation of some Ags can be selectively enhanced by expression of p41. Here we show that p41 can function as a protease inhibitor: 1) the functional and biochemical consequences of p41 expression can be mimicked by inhibiting cysteine proteases in vivo; 2) the amount of intracellular active cysteine proteases is dramatically decreased in p41-positive cells; and 3) a polypeptide corresponding to the p41-unique region is a potent inhibitor of cathepsin L in vitro. These data suggest that p41 can enhance Ag presentation by reducing the proteolytic activity of the Ag-processing compartment, thus protecting a subset of antigenic epitopes from excessive degradation.

Animals↗
PubMed1996

Identification of epitope mimics recognized by CTL reactive to the melanoma/melanocyte-derived peptide MART-1(27-35).

CTL reactivity to the epitope MART-1(27-35), of the melanoma (self) antigen MART-1/melan A is frequently observed in tumor-infiltrating lymphocytes and may be readily elicited from the peripheral blood of melanoma patients that express HLA-A*0201. Available data suggest that these observations contrast with those made for other HLA-A*0201-presented melanoma self antigens regarding the regularity of observed CTL responses. Based on preliminary findings, we hypothesized that the CTL response to MART-1 might be augmented in part by T cell encounters with peptides derived from sources other than MART-1, which show sequence similarity to MART-1(27-35). To test this idea, a protein database search for potential MART-1 epitope mimics was done using criteria developed from analyses of effector recognition of singly-substituted peptide analogues of MART-1(27-35). Synthetic peptides were made for a portion of the sequences retrieved; 12/40 peptides tested were able to sensitize target cells for lysis by one or more anti-MART-1 effectors. The peptides recognized correspond to sequences occurring in a variety of proteins of viral, bacterial, and human (self) origin. One peptide derives from glycoprotein C of the common pathogen HSV-1; cells infected with recombinant vaccinia virus encoding native glycoprotein C were lysed by anti-MART-1 effectors. Our results overall indicate that sequences conforming to the A2.1 binding motif and possessing features essential to recognition by anti-MART-1 CTL occur frequently in proteins. These findings further suggest that T cells might encounter a variety of such sequences in vivo, and that epitope mimicry may play a role in modulating the CTL response to MART-1(27-35).

Amino Acid Sequence↗
PubMed1996

Autoreactive cytotoxic T lymphocytes in human immunodeficiency virus type 1-infected subjects.

A subtractive analysis of peptides eluted from major histocompatibility complex (MHC) class I human histocompatibility leukocyte antigen (HLA)-A2.1 molecules purified from either human immunodeficiency virus type-1 (HIV-1)-infected or uninfected cells was performed using micro high-performance liquid chromatography and mass spectrometry. Three peptides unique to infected cells were identified and found to derive from a single protein, human vinculin, a structural protein not known to be involved in viral pathogenesis. Molecular and cytofluorometric analyses revealed vinculin mRNA and vinculin protein overexpression in B and T lymphocytes from HIV-1-infected individuals. Vinculin peptide-specific CTL activity was readily elicited from peripheral blood lymphocytes of the majority of HLA-A2.1+, HIV+ patients tested. Our observations suggest that atypical vinculin expression and MHC class I-mediated presentation of vinculin-derived peptides accompany HIV infection of lymphoid cells in vivo, with a resultant induction of antivinculin CTL in a significant portion of HIV+ (HLA-A2.1+) individuals.

Amino Acid Sequence↗
PubMed1996

Expression of IFN regulatory factor family proteins in lymphocytes. Induction of Stat-1 and IFN consensus sequence binding protein expression by T cell activation.

Interferon consensus sequence binding protein (ICSBP) is a transcription factor of the IFN regulatory factor (IRF) family. Evidence indicates that this family has a function in the immune system. Unlike other members of the family, ICSBP is expressed exclusively in the immune system. In this work, immunoblot analysis was performed to study expression of ICSBP and other members of the family in various murine lymphocytes. The results show that all IRF family members are expressed constitutively in B cells throughout development, and in resting and activated cells. In contrast, ICSBP expression was undetectable in thymocytes and resting T cells, while all other IRF proteins tested (IRF-1, IRF-2, and ISGF3-gamma) were detected in these cells. Induction of ICSBP (and weakly IRF-1, but not other members) was observed upon activation of T cells following anti-CD3 Ab binding or Con A stimulation. Once T cells were activated, ICSBP was expressed stably in both Th1 and Th2 cells. We show that Stat-1, which binds to the IFN-gamma-responsive element of the ICSBP promoter, was induced following anti-CD3 Ab and Con A stimulation. Stat-1 induction was found in T cells of IFN-gamma+/+, but not of IFN-gamma-/- mice, indicating that T cell activation stimulates the Stat pathway of transcription that is mediated through IFN-gamma. IFN-gamma-activated Stat-1 partly accounted for ICSBP induction in activated T cells, as levels of induction were lower in IFN-gamma-/- than in IFN+/+ T cells. Taken together, these results show that activation of ICSBP is coupled with T cell activation that is partly due to IFN-gamma-induced Stat-1.

Amino Acid Sequence↗
PubMed1996

Binding and presentation of peptides derived from melanoma antigens MART-1 and glycoprotein-100 by HLA-A2 subtypes. Implications for peptide-based immunotherapy.

Cellular immune responses to melanoma-associated Ags are the focus of ongoing studies aimed at developing immunotherapies for treatment of malignant melanoma. Melanoma predominantly affects Caucasians, a population in whom expression of HLA-A2 is prevalent. Among HLA-A2 subtypes, HLA-A*0201 is widely expressed, and HLA-A*0201-restricted, tumor-reactive CTL responses are well studied. We have observed in a group of melanoma patients an unexpectedly high frequency (approximately 20%) of non-HLA-A*0201 subtypes (*0202, *0204, and *0205), and little is known regarding antimelanoma response profiles in patients expressing such subtypes. We analyzed non-HLA-A*0201 peptide response profiles using HLA-A*0201-restricted epitopes from melanoma Ags MART-1/Melan A and glycoprotein 100. Most of these peptides bound to the majority of subtypes tested with 50% inhibitory concentrations less than 500 nM. Recognition of cells pulsed with different peptides (MART-1(27-35), G9(154), and G9(280) Flu M1(58-66)) and expressing different subtype molecules by HLA-A*0201-restricted CTL was limited to only a subset of non-HLA-A*0201 molecules, and the peptide/subtype complexes recognized varied among the effector populations tested. CTL responses elicited from PBL of patients and healthy donors expressing subtypes HLA-A*0202 and HLA-A*0205 suggested significant differences among HLA-A2 subtype function in the context of melanoma Ag presentation. These observations imply the necessity of subtyping patients considered for peptide-based protocols and highlight the need for further study of melanoma-directed cellular responses among patients expressing non-HLA-A*0201 subtypes.

Alleles↗
PubMed1996

Therapy of murine tumors with p53 wild-type and mutant sequence peptide-based vaccines.

The BALB/c Meth A sarcoma carries a p53 missense mutation at codon 234, which occurs in a peptide, termed 234CM, capable of being presented to cytotoxic T lymphocytes (CTL) by H-2Kd molecules (Noguchi, Y., E.C. Richards, Y.-T. Chen, and L.J. Old. 1994. Proc. Natl. Acad. Sci. USA. 91:3171-3175). Immunization of BALB/c mice with bone marrow-derived dendritic cells (DC), generated in the presence of granulocyte macrophage colony-stimulating factor and interleukin 4, and prepulsed with the Meth A p53 mutant peptide, induced CTL that specifically recognized peptide-pulsed P815 cells, as well as Meth A cells naturally expressing this epitope. Immunization with this vaccine also protected naive mice from a subsequent tumor challenge, and it inhibited tumor growth in mice bearing day 7 subcutaneous Meth A tumors. We additionally determined that immunization of BALB/c mice with DC pulsed with the p53 peptide containing the wild-type residue at position 234, 234CW, induced peptide-specific CTL that reacted against several methylcholanthrene-induced BALB/c sarcomas, including CMS4 sarcoma, and rejection of CMS4 sarcoma in vaccination and therapy (day 7) protocols. These results support the efficacy of DC-based, p53-derived peptide vaccines for the immunotherapy of cancer. The translational potential of this strategy is enhanced by previous reports showing that DC can readily be generated from human peripheral blood lymphocytes.

Amino Acid Sequence↗
PubMed1996

A mutated beta-catenin gene encodes a melanoma-specific antigen recognized by tumor infiltrating lymphocytes.

A number of antigens recognized by tumor-reactive T cells have recently been identified. The antigens identified in mouse model systems appear, with one exception, to represent the products of mutated genes. In contrast, most of the antigens recognized by human tumor-reactive T cells reported to date appear to represent the products of non-mutated genes. Here we report the isolation of a cDNA clone encoding beta-catenin, which was shown to be recognized by the tumor-infiltrating lymphocyte (TIL) 1290, a HLA-A24 restricted melanoma-specific CTL line from patient 888. The cDNA clone, which was isolated from the autologous melanoma cDNA library, differed by a single base pair from the published beta-catenin sequence, resulting in a change from a serine to a phenylalanine residue at position 37. Normal tissues from this patient did not express the altered sequence, nor did 12 allogeneic melanomas, indicating that this represented a unique mutation in this patient's melanoma. A peptide corresponding to the sequence between amino acids 29 and 37 of the mutant gene product was identified as the T cell epitope recognized by TIL 1290. The observation that HLA-A24 binding peptides contain an aromatic or hydrophobic residue at position 9 suggested that the change at position 37 may have generated a peptide (SYLDSGIHF) which was capable of binding to HLA-A24, and a competitive binding assay confirmed this hypothesis. The beta-catenin protein has been shown previously to be involved in cell adhesion mediated through the cadherin family of cell surface adhesion molecules. The high frequency of mutations found in members of cellular adhesion complexes in a variety of cancers suggests that these molecules may play a role in development of the malignant phenotype.

Amino Acid Sequence↗
PubMed1996

Distinctive features of the alpha 1-domain alpha helix of HLA-C heavy chains free of beta 2-microglobulin.

Only a few monoclonal antibodies are available with a restricted specificity to HLA-C products. In the present report, we demonstrate that antibody L31, previously shown to react with beta 2m-less (free) class I MHC heavy chains, binds to an epitope (residues 66-68 of the alpha 1 domain alpha helix) present on all the HLA-C alleles corresponding to the accepted (CW1 through CW8) serologic specificities, and on a few HLA-B heavy chains sharing with HLA-C an aromatic residue at position 67. Extensive IEF blot testing of HLA homozygous, EBV-transformed B-lymphoid cells indicates that HLA-C molecules are present at significantly lower levels than HLA-B polypeptides not only at cell surface, as previously demonstrated, but also in total cellular extracts. Testing of metabolically labeled HLA-CW1, -CW5, and -CW6 transfectants and HLA homozygous lymphoid cells, particularly HLA-CW1-expressing cells, demonstrates that the L31 epitope is present on a subpopulation of naturally occurring HLA-C molecules distinct from that identified by antibody W6/32 to beta 2m-associated heavy chains. Pulse-chase experiments demonstrate that this epitope is transiently made available to antibody binding at early biosynthetic stages, but becomes hidden upon assembly with beta 2m. Thus, free HLA-C and other Y/F67+ heavy chains are characterized by distinctive antibody binding features in a region (residues 66-68) included in a previously identified HLA-C restricted motif, which has been suggested to be the primary cause of distinctive features of the antigen-binding groove, low affinity for endogenous peptide antigens and beta 2m, and preferential uptake of exogenous peptides, possibly of viral origin. We also show that HLA-CW1 heavy chains, both free and beta 2m associated, acquire sialilation. Free HLA-CW1 heavy chains are expressed at the cell surface even when unsialilated, albeit at low levels.

Antibodies, Monoclonal↗
PubMed1996

A recombinant single-chain HLA-A2.1 molecule, with a cis active beta-2-microglobulin domain, is biologically active in peptide binding and antigen presentation.

We have constructed a recombinant single-chain human HLA-A2.1 molecule (from A*0201) with a covalently attached beta 2m. This molecule (MSC beta A2.1) can be detected on the surface of transfected beta 2m- human cells by conformational antibodies W6/32 and BB7.2 and by anti-human beta 2m mAb BM-63. The covalent beta 2m, now a domain of the MSC beta A2.1 molecule, does not rescue endogenous Class I surface expression. Instead, it works in cis to achieve correct folding of the single-chain molecule. Immunoprecipitation shows that MSC beta A2.1 is a 60-kDa molecule with no dissociable beta 2m. The half-life of the MSC beta A2.1 molecule on transfected cell surfaces was as long as that of two-chain HLA-A2.1 molecules. The MSC beta A2.1 molecule was active in presentation of HTLV-I Tax 11-19 peptide and an endogenous peptide to specific CTL. MSC beta A2.1 molecules and wild-type HLA-A2.1 molecules on live cells can bind the HBV core peptide 18-27 with comparable affinities. These results show that MSC beta A2.1 molecules retain the functional ability to present both pulsed and endogenous antigens to the appropriate T cells, and thus may be useful components of antiviral vaccines.

Antigen Presentation↗
PubMed1996

Chemical synthesis of phosphorylated peptides of the carboxy-terminal domain of human p53 by a segment condensation method.

A segment condensation method was developed for the chemical synthesis of large (> 90 amino acid) phosphopeptides and was used to produce phosphorylated and non-phosphorylated derivatives of the C-terminal tetramerization and regulatory domains of human p53 (residues 303-393). Efficient condensation synthesis of the 91 residue p53 domain was achieved in two steps. The non-phosphorylated N-terminal segment p53(303-334) (1) and its derivative phosphorylated at serine 315 (1P315), and the non-phosphorylated middle segment p53(335-360) (2), were synthesized as partially protected peptide thioesters in the solid phase using Boc chemistry. The C-terminal segment p53(361-393) (3) and its derivative phosphorylated at serine 392 (3P392) were synthesized as partially protected peptides in the solid phase using Fmoc chemistry. Phosphoamino acid was incorporated into the N-terminal segment (1P315) at the residue corresponding to p53 serine 315 as Boc-Ser(PO3(Bzl)2)-OH during synthesis. Serine 392 in the C-terminal segment was selectively phosphorylated after synthesis by phosphitylation followed by oxidation. A derivative phosphorylated at serine 378 was synthesized in a one-step condensation of the unphosphorylated N-terminal segment (1) and the phosphorylated long C-terminal segment p53(335-393) (2-3P378). Yields of the ligated peptides after removal of the protecting groups and HPLC purification averaged 60% for the first condensation and 35% for the second condensation. All five p53 peptides exhibited monomer-tetramer association as determined by analytical ultracentrifugation. Circular dichroism spectroscopy revealed that phosphorylation at Ser315 increased the alpha-helical content, which was abolished when Ser392 also was phosphorylated, suggesting an interaction between N-terminal and C-terminal residues of the C-terminal domain of p53.

Amino Acid Sequence↗
PubMed1996

Conformational changes induced in the protein tyrosine kinase p72syk by tyrosine phosphorylation or by binding of phosphorylated immunoreceptor tyrosine-based activation motif peptides.

A critical event in signaling in immune cells is the interaction of Syk or ZAP-70 protein tyrosine kinases with multisubunit receptors that contain an approximately 18-amino-acid domain called the immunoreceptor tyrosine-based activation motif (ITAM). Tyrosine-phosphorylated Syk from activated cells was in a conformation different from that in nonstimulated cells as demonstrated by changes in immunoreactivity. The addition of tyrosine-diphosphorylated ITAM peptides resulted in a similar conformational change in Syk from nonactivated cells. The peptides based on FcepsilonRIgamma were more active than those based on Fcepsilon RIbeta. In vitro autophosphorylation of Syk was dramatically enhanced by the addition of the diphosphorylated ITAM peptides. The conformational change and the enhanced autophosphorylation required the presence of both phosphorylated tyrosines on the same molecule. These conformational changes in Syk by tyrosine phosphorylation or binding to diphosphorylated ITAM could be critical for Syk activation and downstream propagation of intracellular signals.

Amino Acid Sequence↗
PubMed1996

Mutational analysis of Lck in CD45-negative T cells: dominant role of tyrosine 394 phosphorylation in kinase activity.

The CD45 tyrosine phosphatase has been reported to activate the src family tyrosine kinases Lck and Fyn by dephosphorylating regulatory COOH-terminal tyrosine residues 505 and 528, respectively. However, recent studies with CD45- T-cell lines have found that despite the fact that Lck and Fyn were constitutively hyperphosphorylated, the tyrosine kinase activity of both enzymes was actually increased. In the present study, phosphoamino acid analysis revealed that the increased phosphorylation of Lck in CD45- YAC-1 T cells was restricted to tyrosine residues. To understand the relationship between tyrosine phosphorylation and Lck kinase activity, CD45- YAC-1 cells were transfected with forms of Lck in which tyrosines whose phosphorylation is thought to regulate enzyme activity (Tyr-192, Tyr-394, Tyr-505, or both Tyr-394 and Tyr-505) were replaced with phenylalanine. While the Y-to-F mutation at position 192 (192-Y-->F) had little effect, the 505-Y-->F mutation increased enzymatic activity. In contrast, the 394-Y-->F mutation decreased the kinase activity to very low levels, an effect that the double mutation, 394-Y-->F and 505Y-->F, could not reverse. Phosphopeptide analysis of tryptic digests of Lck from CD45- YAC-1 cells revealed that it is hyperphosphorylated on two tyrosine residues, Tyr-505 and, to a lesser extent, Tyr-394. The purified and enzymatically active intracellular portion of CD45 dephosphorylated Lck Tyr-394 in vitro. These results demonstrate that in addition to Tyr-505, CD45 can dephosphorylate Tyr-394, and that in the absence of CD45 the hyperphosphorylation of Tyr-394 can cause an increase in the kinase activity of Lck despite the inhibitory hyperphosphorylation of Tyr-505. Therefore, Lck kinase activity is determined by the balance of activating and inhibitory tyrosine phosphorylations that are, in turn, regulated by CD45.

Amino Acid Sequence↗
PubMed1995

A p53-independent pathway for activation of WAF1/CIP1 expression following oxidative stress.

Incubating human cells in diethylmaleate (DEM) depletes the intracellular pool of reduced glutathione (GSH) and increases the concentration of oxidative free radicals. We found that DEM-induced oxidative stress reduced the ability of p53 to bind its consensus recognition sequence and to activate transcription of a p53-specific reporter gene. Nevertheless, DEM treatment induced expression of WAF1/CIP1 but not GADD45 mRNA. The fact that N-acetylcysteine, a precursor of GSH that blocks oxidative stress, prevented WAF1/CIP1 induction by DEM suggests that WAF1/CIP1 induction probably was a consequence of the ability of DEM to reduce intracellular GSH levels. DEM induced WAF1/CIP1 expression in Saos-2 and T98G cells, both of which lack functional p53 protein. DEM treatment did not produce an increase in membrane-associated protein kinase C, but ERK2, a mitogen-activated protein kinase, was phosphorylated in a manner consistent with ERK2 activation. DEM treatment also produced a dose-dependent delay in cell cycle progression, which at low concentrations (0.25 mM) consisted of a G2/M arrest and at higher concentrations (1 mM) also involved G1 and S phase delays. Our results indicate that oxidative stress induces WAF1/CIP1 expression and arrests cell cycle progression through a mechanism that is independent of p53. This mechanism may provide for cell cycle checkpoint control under conditions that inactivate p53.

Animals↗