Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A full-length alpha 2-macroglobulin (alpha 2M) cDNA was cloned into the episomal expression vectors pREP7 and pMEP4. Electroporation of the cell lines WI-L2-729HF2, U-937, K-562 and an Epstein-Barr virus-transformed cell line resulted in stable transfectants only with K-562 cells. Stable expression was obtained exclusively with pMEP4-alpha 2M and was driven from the inducible human metallothionein IIA promoter. Expression of the wild-type alpha 2M cDNA resulted in a recombinant protein (r alpha 2M) that could not be distinguished from plasma alpha 2M (p-alpha 2M): the transfected K-562 cells secreted tetrameric alpha 2M with intact internal thiol esters, a functional bait domain and a latent receptor-binding domain. r alpha 2M inhibited trypsin and elastase from cleaving a high-molecular-mass substrate. When the Cys-949 involved in the formation of the internal thiol ester was mutated to tyrosine (C949Y-r alpha 2M), a tetrameric alpha 2M was secreted, with the electrophoretic mobility of methylamine-treated p-alpha 2M (p-alpha 2M/MA) and with a functional receptor-binding domain. The C949Y-r alpha 2M did not possess proteinase-inhibiting capacity. Heterozygosity was mimicked by co-transfecting the K-562 cells with wild-type and mutant expression vectors. In this case, r alpha 2M was secreted with zero, one, two, three or four internal thiol esters. A comparison of the interaction of interleukin 1 beta and basic fibroblast growth factor with native p-alpha 2M, p-alpha 2M/MA and the mutant C949Y-r alpha 2M revealed that when assayed under nondenaturing conditions, no binding occurred to 'slow' p-alpha 2M whereas quantitatively similar binding was observed to 'fast' p-alpha 2M/MA and C949Y-r alpha 2M. Covalent binding, however, was essentially limited to p-alpha 2M/MA, suggesting the involvement of Cys-949 in the process. Covalent binding of insulin, on the contrary, was only observed when it was present during hydrolysis of the internal thiol esters of p-alpha 2M by trypsin treatment, and thus involves the activated Glx residue.
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PMID:Synthesis of a Cys949Tyr alpha 2-macroglobulin thiol ester mutant: co-transfection with wild-type alpha 2-macroglobulin in an episomal expression system. 749 11

The supernatant of a cell line of squamous cell carcinoma of the head and neck (SCCHN), PCI-50, was previously shown to induce activation, promote proliferation and increase antitumor cytotoxicity of freshly purified human natural killer (NK) cells and CD4+ T lymphocytes [Arch Otolaryngol Head Neck Surg (1994) in press]. This supernatant was found also to promote the growth of a variety of hematopoietic cell lines, including Jurkat, THP-1, K562, NK-92 or Epstein-Barr-virus-transformed B cell lines. The Jurkat cell line was selected as a reporter cell in an 18-h proliferation assay established to measure the growth-promoting activity of PCI-50 supernatant. The presence of soluble tumor-derived factors able to induce proliferation of Jurkat cells was demonstrated in the supernatant produced by several other SCCHN cell lines but not in that produced by a gastric cancer cell line (HR) or renal cell carcinoma line (5117G8). The growth-promoting PCI-50 supernatant was shown to contain 28 +/- 0.5 pg/ml interleukin-6 (IL-6) in vitro but was negative for interferon gamma, IL-1, IL-2, IL-4, tumor necrosis factor alpha, granulocyte/macrophage-colony-stimulating factor and IL-12. The addition of any of these recombinant cytokines to Jurkat cell cultures did not significantly promote growth, while PCI-50 supernatant was consistently growth-stimulatory. This supernatant neither enhanced intracellular Ca2+ concentration in Jurkat cells nor induced up-regulation of activation antigens on the cell surface, although it supported growth of Jurkat cells in the absence of IL-2. The growth-promoting activity in the PCI-50 supernatant was acid-labile at pH 2 for 4 h, heat-resistant at 96 degrees C for 1 h and sensitive to treatments with trypsin and pepsin. Preincubation of the PCI-50 producer cells with tunicamycin or cyclohexamide reduced the level of growth-promoting activity in the supernatant. A partial purification of this activity was achieved using Amicon filtration, chromatography on concanavalin-A-Sepharose and then a hydroxyapatite column and high-pressure liquid chromatography gel filtration. The partially purified glycoprotein had a molecular mass of 50-70 kDa, as determined by gel filtration.
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PMID:Proliferation of hematopoietic cell lines induced by a soluble factor derived from human squamous cell carcinomas of the head and neck. 800 Oct 29

The infection of human peripheral blood B cells with Epstein-Barr Virus (EBV), induced the production of suppressor factor(s) which were released into the supernatant of the B-cell cultures. The induction of suppressive activity was independent of T-cell presence. The suppression was exhibited both against T-cell activity (MLR and mitogenic stimulation) as well as against B-cell mitogenic stimulation of human or murine B lymphocytes. The suppressive factor(s) was of a low molecular weight (equal or less than 5,000), resistant to trypsin and heating at 80 degrees C and its activity was partially inhibited by neuraminidase treatment. These findings indicate that the suppressive factor(s) is not correlated to immunoglobulin production, is not apparently of a protein nature, and might be of ganglioside or siaylated glycoprotein structure. Our present findings suggest that, in addition to T cells, B cells might also play an immunoregulatory role in the expression of immune response potential.
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PMID:Secretion of suppressor factors by EBV infected B cell lines. 891 98

Antibodies to glutamic acid decarboxylase-65 (GAD65) are present in a number of autoimmune disorders, such as insulin-dependent (type 1) diabetes mellitus (IDDM), stiff man syndrome, and polyendocrine autoimmune disease. Antibodies to GAD in IDDM patients usually recognize conformation-dependent regions on GAD65 and rarely bind to the second isoform, glutamic acid decarboxylase-67 (GAD67). In contrast, those present in stiff man syndrome and polyendocrine disease commonly target the second isoform (GAD67) and include antibodies that are less dependent on the conformation of the molecule. By immortalizing peripheral blood B cells with Epstein-Barr virus, we have generated three human IgG autoantibodies, termed b35, b78, and b96, to GAD65 from one patient with multiple autoantibodies to endocrine organs and Graves' disease. All three autoantibodies are of the IgG1 isotype, with islet cell activity, and do not react with GAD67. The regions on GAD65 recognized by the three autoantibodies have been investigated by immunoprecipitation with a series of chimeras, by binding to denatured and reduced antigens, and using protein footprinting techniques. Using chimeric GAD proteins, we have shown that b35 targets the IDDM-E1 region of GAD65 (amino acids 240-435) whereas both b78 and b96 target the IDDM-E2 region of GAD65 (amino acids 451-570). Furthermore, examination of binding to recombinant GAD65 and GAD67 by Western blotting revealed some differences in epitope recognition, where only b78 bound denatured and reduced GAD65. However, b35, b78, and b96 autoantibodies had different footprinting patterns after trypsin treatment of immune complexes with GAD65, again indicating different epitope recognition. Our results indicate that antibodies to GAD65 present in nondiabetic patients with multiple autoantibodies to endocrine organs show similarities to those in IDDM (by targeting IDDM-E1 and IDDM-E2 regions of GAD65) as well as subtle differences in epitope recognition (such as binding to denatured and reduced GAD65 and by protein footprinting). Thus, the GAD65 epitopes recognized by autoantibodies in different autoimmune diseases may overlap and be more heterogeneous than previously recognized.
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PMID:Human B cells secreting immunoglobulin G to glutamic acid decarboxylase-65 from a nondiabetic patient with multiple autoantibodies and Graves' disease: a comparison with those present in type 1 diabetes. 925 51

Interleukin-15 (IL-15) is a potent regulator of T-, B-, and natural killer cell proliferation and displays unusually tight controls of secretion. Even though IL-15 mRNA is constitutively expressed in monocytes/macrophages and is upregulated by a variety of stimuli, evidence for IL-15 cytokine secretion is only found exceptionally, eg, conditions of pathological, chronic inflammation. This raises the possibility that monocytes express membrane-bound IL-15 rather than secrete it. The current study explores this hypothesis. We demonstrate here that biologically active IL-15 is indeed detectable in a constitutively expressed, membrane-bound form on normal human monocytes, as well as on monocytic cell lines (MONO-MAC-6, THP-1, and U937), but not on human T or B cells (MT4, M9, C5966, JURKAT, DAUDI, RAJI, and Epstein-Barr virus-immortalized B-cell clones). Furthermore, cell surface-bound IL-15 is upregulated upon interferon-gamma stimulation. Interestingly, monocyte/macrophage inhibitory cytokines such as IL-4 and IL-13 fail to downregulate both constitutive and induced cell-surface expression of IL-15. Membrane-bound IL-15 does not elute with acetate buffer or trypsin treatment, suggesting that it is an integral membrane protein and that it is not associated with the IL-15 receptor complex. Finally, membrane-bound IL-15 stimulates T lymphocytes to proliferate in vitro, indicating that it is biologically active. These findings enlist IL-15 in the fairly small family of cytokines for which the presence of a biologically active membrane-bound form has been demonstrated (eg, IL-1, tumor necrosis factor-alpha, and IL-10) and invites the speculation that most of the biological effects of IL-15 under physiological conditions are exerted by the cell surface-bound form.
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PMID:Human monocytes constitutively express membrane-bound, biologically active, and interferon-gamma-upregulated interleukin-15. 1023 6

We investigated the expression of interferon gamma (IFN-gamma)-regulated subunits and the enzymatic activity of proteasomes purified from tumor-derived and normal B lymphocytes representing different stages of B-cell activation/differentiation. The catalytic beta subunits (Lmp2 and Lmp7) and the regulatory subunits (PA28alpha and PA28beta) were expressed at equally high levels in Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs), freshly isolated B-chronic lymphocytic leukemia (B-CLL) cells and normal CD23(-) B lymphocytes. Lmp2 and Lmp7 were selectively down-regulated in germinal center cell-derived Burkitt's lymphoma (BL) and Hodgkin's lymphoma (HD) cell lines. There was a direct correlation between the expression of Lmp2/7 and the chymotrypsin and trypsin-like activities in proteasomes purified from LCLs, BLs and CLL cells, whereas 5 HD cell lines expressing B or T-cell markers exhibited a variable pattern of subunit expression and enzymatic activity. Poor hydrolysis of the fluorogenic substrates by proteasomes from BL cells correlated with a distinct pattern of cleavage of a reference 50mer peptide, production of different sets of degradation products and significantly reduced recovery of a known cytotoxic T-lymphocyte (CTL) target epitope. The enzymatic activity of proteasomes from normal CD23(-) "resting" B lymphocytes resembled that of BL cells in spite of high Lmp2/7 expression. This pattern was not reversed by treatment with the B-cell mitogen, lipopolysaccharide (LPS). The results suggest that different stages of B-cell activation/differentiation are associated with distinct profiles of IFN-gamma-regulated subunit composition and enzymatic activity of the proteasome. This may have important implications for the analysis and manipulation of tumor-specific immune responses.
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PMID:Variations in proteasome subunit composition and enzymatic activity in B-lymphoma lines and normal B cells. 1109 9

The identification of proteins differentially expressed between cancer and normal cells is vital for the development of cancer diagnostics, therapeutics and vaccines. Using a ProteinChip Biomarker System (Ciphergen Biosystems, Fremont, CA) which combines ProteinChip technology with time-of-flight mass spectrometry, we have developed a simple method to screen and identify differentially secreted proteins from tumor cell lines. Mass spectra of the range of proteins secreted from normal B-cells were generated along with those secreted from Epstein-Barr virus transformed B-cells. A mass peak at m/z = 4972.1 that was highly over-represented in the transformed B-cell line was chosen for identification and purified by reversed phase chromatography with concomitant monitoring of fractions by SELDI-TOF MS. The resulting purified protein was digested with trypsin and the peptide masses derived from the SELDI-TOF spectrum were used to search the public databases for protein identification. Fragment matching of the resulting peptides identified the protein as thymosin beta-4. Using LC-electrospray ionization MS/MS, the identity of this protein was confirmed. Thymosin beta-4 is a known marker in LCLs establishing the utility of this method to discover and identify proteins differentially expressed between cancers and their matched normal counterparts.
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PMID:Use of ProteinChip array surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) to identify thymosin beta-4, a differentially secreted protein from lymphoblastoid cell lines. 1283 98

Mature Epstein-Barr virus (EBV) was purified from the culture medium of infected lymphocytes made functionally conditional for Zta activation of lytic replication by an in-frame fusion with a mutant estrogen receptor. Proteins in purified virus preparations were separated by gradient gel electrophoresis and trypsin-digested; peptides were then analyzed by tandem hydrophobic chromatography, tandem MS sequencing, and MS scans. Potential peptides were matched with EBV and human gene ORFs. Mature EBV was mostly composed of homologues of proteins previously found in a herpes virion. However, EBV homologues to herpes simplex virus capsid-associated or tegument components UL7 (BBRF2), UL14 (BGLF3), and EBV BFRF1 were not significantly detected. Instead, probable tegument components included the EBV and gamma-herpesvirus-encoded BLRF2, BRRF2, BDLF2 and BKRF4 proteins. Actin was also a major tegument protein, and cofilin, tubulin, heat shock protein 90, and heat shock protein 70 were substantial components. EBV envelope glycoprotein gp350 was highly abundant, followed by glycoprotein gH, intact and furin-cleaved gB, gM, gp42, gL, gp78, gp150, and gN. BILF1 (gp64) and proteins associated with latent EBV infection were not detected in virions.
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PMID:Proteins of purified Epstein-Barr virus. 1553 16


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