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K Wang

Publications and source records attributed to K Wang.

At least 433 records · Page 24Linked to original sources
PubMed1994

Nucleotide binding of the C-terminal domains of the major histocompatibility complex-encoded transporter expressed in Drosophila melanogaster cells.

The C-terminal domains of the mouse transporter associated with antigen processing (TAP) were expressed as soluble proteins in Drosophila melanogaster cells and labeled by [alpha-32P]8-azido-ATP after UV-irradiation. The relative potencies of the nucleotides in preventing azido-ATP labeling were in the order of ATP > GTP > CTP > ITP > UTP for both the TAP1 and TAP2 C-terminal domains, suggesting ATP to be the natural substrate of the transporter. Our data provide the first evidence that the individual C-terminal domain of either TAP1 or TAP2 can be expressed as a functional ATP-binding protein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Displacement of housekeeping proteasome subunits by MHC-encoded LMPs: a newly discovered mechanism for modulating the multicatalytic proteinase complex.

The degradation of cytoplasmic antigens to peptides presented by class I MHC molecules is thought to be mediated by the ubiquitin/proteasome pathway. Support for this view came from our observation that the subunit composition of proteasomes can be changed by interferon-gamma (IFN-gamma) treatment. Thereby two subunits, LMP2 and LMP7, which are encoded in the MHC class II region, are incorporated into the proteasomal complex, whereas other subunits disappear. In the experiments reported in this communication we studied the subunit changes occurring in cell lines where the expression of LMP2 or LMP7 can be regulated individually either by IFN-gamma induction or by applying a new system to control the expression of transfected LMPs. In both situations LMP2 induction leads exclusively to the disappearance of housekeeping subunit 2, whereas LMP7 affects only subunit 10. Subunit 2 was found to be 76% homologous to LMP2. Since incorporation of LMP2 into the proteasomal complex prevents processing of the subunit 2 precursor, we conclude that LMP2 displaces subunit 2 during assembly. Subunit displacement is most likely a general mechanism to modulate the catalytic activity of the proteasomal complex without changing its structure. Furthermore, the controlled incorporation of transfected subunits into the complex offers a new approach to study proteasome function in vivo.

Amino Acid Sequence↗
PubMed1994

Interaction of MHC class I molecules with the transporter associated with antigen processing.

The transporter associated with antigen processing (TAP) delivers cytosolic peptides into the endoplasmic reticulum (ER) where they bind to nascent class 1 histocompatibility molecules. Class 1-peptide complexes are then displayed at the cell surface for recognition by cytotoxic T lymphocytes. Immunoprecipitation of either TAP or class 1 molecules revealed an association between the transporter and diverse class 1 products. TAP bound preferentially to heterodimers of the class 1 heavy chain and beta 2-microglobulin, and the complex subsequently dissociated in parallel with transport of class 1 molecules from the ER to the Golgi apparatus. The TAP-class 1 complexes could also be dissociated in vitro by the addition of class 1-binding peptides. The association of class 1 molecules with TAP likely promotes efficient capture of peptides before their exposure to the lumen of the ER.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

The chaperone activity of bovine alpha crystallin. Interaction with other lens crystallins in native and denatured states.

It has previously been reported that alpha crystallin (alpha) a major lens protein composed of alpha A and alpha B subunits, can act as a chaperone interacting with other proteins to prevent heat-induced insolubilization. It is now shown that with gamma (gamma), beta L (beta L), and beta H (beta H), other major crystallin groups, this interaction occurs exclusively with soluble denatured protein. Based on studies primarily conducted with the gamma and the beta L crystallins, there is at least one binding site per alpha monomer (alpha m). This conclusion is derived from the following evidence. The binding of soluble denatured protein to alpha increases in a linear stoichiometric manner until a 1:1 ratio of alpha m to gamma or to the presumed (beta L)m is achieved. This is based upon determination of the apparent molecular weight of the alpha-denatured protein aggregate with a calibrated TSK-G4000 SW column and on the determination of the relative masses from the areas of the aggregate peak and those of the reactants. SDS-polyacrylamide gel electrophoresis confirms that the aggregates contain the presumed components following reaction with either gamma, beta L, or beta H. Studies in which gamma or beta L crystallins have been independently heat denatured indicate that species representing 50% of the gamma population and 30% of beta L population have not heat denatured under the conditions employed. When the abundance of the denatured soluble protein exceeds that of the alpha subunits present in the macromolecular complex, further interaction occurs leading to a loss of solubility of the complex. A small increase in the size of the complex remaining in solution is also observed. The results contribute to understanding earlier observations that soluble native low molecular weight alpha species cannot be found in the inner regions of old human lenses but have shifted to large aggregates containing other crystallin components. The work tentatively suggests that the interaction rates of alpha with denatured soluble crystallins are gamma > beta L > beta H.

Animals↗
PubMed1994

Conformational studies of a two-module fragment of nebulin and implications for actin association.

Nebulin, a family of giant myofibrillar proteins of 700-900 kDa, has been proposed as a length-regulating template for the thin filaments of skeletal muscle. In the present study, the conformational states of a two-module nebulin fragment (ND8) were investigated by circular dichroism, steady-state fluorescence, fluorescence lifetime, and one-dimensional and two-dimensional NMR techniques. We observed the following: (a) Contrary to the predicted high alpha-helical content by computer analysis, CD spectra of ND8 indicated only a maximum of 10% alpha-helix and 25% beta-sheet in a variety of buffers; (b) The presence of increasing concentrations of trifluoroethanol (TFE) promoted the formation of alpha-helix and ND8 contained 50% alpha-helix at 67% TFE; (c) Measurement of fluorescence lifetime, anisotropy, and CD of tyrosines in ND8 in various concentrations of TFE indicates that tyrosines are incorporated into the newly formed helical segments; (d) Preliminary correlation spectroscopy and nuclear Overhauser enhancement spectroscopy NMR spectra of ND8 confirmed the formation of alpha-helical structure and identified sites of helical segments in 30% TFE around the highly conserved tyrosine residues. These data suggest that the conformation of nebulin and its mode of interaction with actin are distinct from the helical tropomyosin.

Actins↗
PubMed1994

Organization, sequence, and function of 34.5 kb of genomic DNA encompassing several murine T-cell receptor alpha/delta variable gene segments.

A cosmid-bearing murine genomic DNA, encompassing several T-cell receptor variable alpha/delta gene segments, has been sequenced using shotgun DNA cloning methodology coupled with fluorescence-based high-through-put DNA sequencing technology. This region, spanning 34.5 kb, contains a pseudogene V alpha gene segment (psi V alpha 16.1), a V delta gene segment (V delta 2), and a variable gene segment that has been reported to be expressed with both C alpha (V alpha 6) and C delta (V delta 3). Therefore, this cosmid is the ideal vehicle for examining the possible control sequences that may be involved in determining whether a V gene segment associates with either C alpha or C delta. Polymerase chain reaction experiments demonstrate that the two functional variable gene segments (V delta and V alpha/delta) are expressed individually with both C alpha and C delta genes as mRNA, indicating a permissiveness in their expression patterns. In addition, a variety of genomic sequence-related features have been identified.

Amino Acid Sequence↗
PubMed1994

A comparison between preoperative magnetic resonance and intraoperative ultrasound tumor volumes and margins.

A major obstacle in surgical neuro-oncology is differentiating the interface between tumor and normal brain. Twenty-two brain tumors were evaluated preoperatively with magnetic resonance imaging. Intraoperative ultrasonography was used to guide surgical resection of these tumors, and results were compared with surgical and pathologic findings. Ultrasound tumor volume estimates were larger than T1 gadolinium-enhanced and T1 non-gadolinium-enhanced volumes, but these differences did not reach statistical significance. Similarly T2 volumes were larger than the corresponding sonographic volumes, except for the subset of low-grade gliomas, and in that instance the difference was small, but again the differences were not statistically significant. Ultrasonography enhanced identification of infiltrating tumor cells beyond falsely underestimated tumor margins as defined by T1 images. Ultrasound images helped differentiate edema as seen on T2 images from solid tumor and normal brain. The information gained from ultrasound images can be used to enhance tumor resection and improve patient survival and quality of life.

Adolescent↗
PubMed1994

Epitope specificity and T cell receptor usage in type II collagen induced autoimmune ear disease.

An immune response directed against type II collagen (CII) has been reported in several autoimmune diseases including the animal models of collagen-induced arthritis (CIA) and collagen-induced autoimmune ear disease (CIAED). In this communication, we have found that T cells from type II collagen-immunized DBA/1-lac could transfer auricular chondritis to naive mice. The T cells from type II collagen-immunized H-2r and H-2q mice recognize different epitopes from the CB11 peptide of CII. The CII-specific T cells from H-2q background mice recognize peptide residues p121-147 (P1) but do not respond to residues p211-247 (P2). The T cells of H-2r mice immunized with CII respond better to P2 rather than P1. By altering certain amino acids within these epitopes, the response of CII-specific TCR to antigen has been increased or abolished. Our results suggest that the lysine residues at positions 129, 141, and 147 in P1, the arginine residue at position 227, and glutamic acid at position 230 in P2 might play an important role in the trimolecular interaction. Ten clonally distinct T cell hybridomas specific for CII have been established from H-2r B10.RIII mice and the beta chains of their TCR have been analyzed. Three subfamilies, V beta 1, V beta 6, and V beta 8, were utilized with dominant expression of V beta 8 (60%). This is quite similar to the pattern found in type II collagen-induced arthritis in H-2q mice. This preferential use of V beta 8 in CIAED implies that an immunotherapy may make it possible to control this autoimmune disease, even in a MHC-diverse situation.

Amino Acid Sequence↗
PubMed1994

The human T-cell receptor TCRAC/TCRDC (C alpha/C delta) region: organization, sequence, and evolution of 97.6 kb of DNA.

We sequenced and analyzed 97.6 kb of new DNA sequence containing the human TCRAC (C alpha) and TCRDC (C delta) genes as well as the TCRDV3 (V delta 3) and 61 different TCRAJ (J alpha) gene segments and compared its organization and structure to the previously described mouse T-cell receptor TCRAC/TCRDC (C alpha/C delta) region. A comprehensive nomenclature, consistent with the IUIS nomenclature committee recommendations, for both human and mouse TCRAJ gene segments is presented. In the human sequence, we identified 20 new TCRAJ gene segments and obtained the germline sequence for 23 additional TCRAJ gene segments known from cDNA clones. Using the sequence data obtained from the human TCRAC/TCRDC region, we have extended a polymerase chain reaction-based assay to test for the expression of the individual TCRAJ gene segments. At least five TCRAJ pseudogene segments were identified by sequence criteria. Like the murine TCRAC/TCRDC sequence, this sequence contains a high level of coding sequence, with over 6.6% of the total sequence being transcribed. Comparison of the human sequence with the previously reported mouse DNA sequence reveals homologous counterparts for the variable and joining (J) gene segments and both constant genes. Eleven new J pseudogene segments have been identified in the mouse TCRAC/TCRDC sequence through the use of human and mouse sequence comparisons. In terms of structure and organization, this region of the human and mouse genome appears to be remarkably conserved.

Amino Acid Sequence↗
PubMed1994

Organization of the V gene segments in mouse T-cell antigen receptor alpha/delta locus.

The mouse T-cell receptor (TCR) alpha/delta locus was mapped using 17 V alpha and 4 V beta subfamily-specific probes. Four complementary methods were used: (1) an estimate of the V gene repertoire by Southern blot analysis of genomic DNA with subfamily-specific probes; (2) an analysis of V gene segments deleted by TCR gene rearrangements from a panel of T-cell tumors and hybridomas; (3) an analysis of overlapping clusters of cosmid clones; and (4) an analysis of large DNA fragments separated by field-inversion gel electrophoresis. The alpha/delta locus spans about 1 Mb. The distance between the 3'-most V gene segment (V delta 1) and the delta constant gene (C delta) is no more than 150 kb. Sixty-six V gene segments have been mapped physically on cosmids. The members of individual V alpha gene segment subfamilies are dispersed throughout the locus. In contrast, the V delta gene segments V delta 1 to 5 are clustered at the 3' end of the V gene segment cluster. At least two DNA segment duplications, 45 to 80 kb in length, are present in the locus. These data provide information on the evolution of the alpha/delta locus and on organization features that might influence the expression of specific V gene segments in gamma delta cells.

Animals↗
PubMed1994

Structural analysis of the mouse T-cell receptor Tcra V2 subfamily.

Cosmid clones containing T-cell receptor Tcra V2 subfamily gene segments have been isolated from a BALB/c cosmid library and subjected to DNA sequence analysis. The V gene segments in the Tcra V2 subfamily differ from each other by 3%-7% at the nucleotide level and 5%-16% at the amino acid level. T-cell receptor Tcra V2 gene segment polymorphisms have been identified in the B10.PL and PL/J mouse strains with a Tcra V2 subfamily-specific probe. These V gene segment polymorphisms may cause the differential Tcra V gene usage in induced experimental allergic encephalomyelitis between B10.PL and PL/J mice.

Amino Acid Sequence↗
PubMed1994

The expression of mouse T-cell receptor TCRDV genes in BALB/c spleen.

The rearrangement and expression of six different mouse T-cell receptor TCRDV (V delta) gene subfamilies have been studied in BALB/c mouse spleen. The results show that all the TCRDV gene segments studied can be rearranged and expressed with both the TCRA (alpha) and the TCRD (delta) chain. The apparently restricted and separated V gene repertoire for the TCRD and TCRAT-cell receptor may result from thymus and peripheral selection rather than from selective rearrangement in the DNA level. Several J gene segments show much higher concentration in spleen with TCRDV gene segments, however, these J gene segments do not tend to be located at either end of the J gene cluster.

Amino Acid Sequence↗
PubMed1994

Double immunofluorescence staining of Fos and Jun in the hypothalamus of the rat.

The nuclear factor Fos participates in the transcriptional regulation of genes that contain a functional AP-1 binding site. Hyperosmotic stress induces Fos-like immunoreactivity in neurons of the hypothalamus. Fos appears to depend on the co-expression of the nuclear factor Jun, with which it dimerizes, to complete its regulatory role. The immunocytochemical co-localization of both peptides, however, has not been reported. The present study was designed to analyze the distribution of Fos and Jun by double immunofluorescence staining in Long-Evans rats that were osmotically challenged by a single intraperitoneal injection of 1.5 M NaCl. Non-injected and isotonic saline-injected animals were used as controls. Hypertonic saline injection induced Jun immunoreactivity in cell nuclei in the supraoptic nucleus, paraventricular nucleus, and median preoptic nucleus. The immunofluorescence for Jun was strong in the supraoptic and paraventricular nuclei, but weak in the median preoptic nucleus. The immunofluorescence for Fos in all 3 nuclei followed a similar pattern to that for Jun. Double immunofluorescence staining revealed co-localization of Jun with Fos in 87.4% of the cells of the supraoptic nucleus. Neither Jun nor Fos immunofluorescence was detected in control animals. The data support a role for Jun in transcriptional regulation of genes in hypothalamic neurons during acute hyperosmotic stress. Moreover, the findings are compatible with the suggestion that Fos and Jun act cooperatively in the regulation of gene transcription in neuroendocrine systems involved in the control of water balance during acute hyperosmotic stimulation.

Animals↗
PubMed1994

BALB/c substrain differences in susceptibility to Theiler's murine encephalomyelitis virus-induced demyelinating disease.

We report differences among BALB/c substrains in susceptibility to Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease, an immune-mediated inflammatory demyelinating disease and experimental model for human multiple sclerosis. BALB/cJ and BALB/cAnNCr mice are susceptible, while BALB/cByJ and BALB/cCum are resistant. Hybrids between BALB/cBy and BALB/cAnNCr were intermediate, although closer to the resistant parent. Backcrosses gave results compatible with differential susceptibility being related to a single segregating locus. Exposure of resistant BALB/cByJ mice to low dose irradiation, 2 days prior to infection, rendered them susceptible to TMEV-induced demyelination. The susceptibility pattern of TMEV-induced demyelinating disease among BALB/c substrains is distinct from those of several autoimmune disorders.

Animals↗
PubMed1994

The chromatographic behaviour of cephalosporins in gel filtration chromatography, a novel method to separate high molecular weight impurities.

The interaction between cephalosporins and the dextran matrix of Sephadex gel in gel filtration chromatography has been thoroughly studied. Twelve cephalosporins with specific structures were examined under different chromatographic conditions, including 12 different mobile phases comprising inorganic or organic compounds of different charge or/and density of electrons on their negative ions, different types of Sephadex gel (Sephadex G-10 and Sephadex G-50) and different flow rates. It was found that the more negative the charge or/and density of electrons on the negative ions of buffer components, the more was the adsorption of cephalosporins on the solid phase; this indicated tht the mobile phase played an important rôle in gel filtration chromatography for cephalosporins. By choice of suitable chromatographic conditions, optimum separation of high molecular weight impurities from cephalosporins could be achieved. The novel method could be used as a routine method for the quality control of cephalosporin preparations.

Cephalosporins↗