Search PubMed⌕ Search

Biomedical subjects

J Zhou

Publications and source records attributed to J Zhou.

At least 793 records · Page 44Linked to original sources
PubMed1995

The tomato gene Pti1 encodes a serine/threonine kinase that is phosphorylated by Pto and is involved in the hypersensitive response.

The Pto gene encodes a serine/threonine kinase that confers resistance to bacterial speck disease in tomato. Using the yeast two-hybrid system, we identified a second serine/threonine kinase, Pto-interacting 1 (Pti1), that physically interacts with Pto. Cross-phosphorylation assays revealed that Pto specifically phosphorylates Pti1 and that Pti1 does not phosphorylate Pto. Fen, another serine/threonine kinase from tomato that is closely related to Pto, was unable to phosphorylate Pti1 and was not phosphorylated by Pti1. Expression of a Pti1 transgene in tobacco plants enhanced the hypersensitive response to a P. syringae pv. tabaci strain carrying the avirulence gene avrPto. These findings indicate that Pti1 is involved in a Pto-mediated signaling pathway, probably by acting as a component downstream of Pto in a phosphorylation cascade.

Amino Acid Sequence↗
PubMed1995

Early phase in the infection of cultured cells with papillomavirus virions.

The fate of full bovine papillomavirus (BPV) virions and virus-like particles after binding to C127 or CV-1 cells was studied by electron microscopy and indirect immunofluorescence. After incubation at 4 degrees for 1 hr, BPV virions were found to be bound to the plasma membrane, and most viruses were absorbed by the cells after 30 min incubation at 37 degrees. Ninety minutes after the virions had been bound to the plasma membrane, the uptake of the virions was completed and most of the antigen was found to be localized in the nucleus. The viruses were transported in phagosomes and the uptake and transportation could be inhibited by cytochalasin B and taxol, suggesting the possible involvement of microfilaments and microtubules in the virus particle uptake and transportation. The capsid proteins could be detected for about 14 hr, until degradation and deposit of the viral antigen in the Golgi complexes. Although binding to the plasma membrane and uptake of virions into large cytoplasmic vesicles could be monitored by electron microscopy, no complete virions were observed in the nucleus of infected cells despite a very strong nuclear fluorescent staining for both L1 and L2 proteins. This may indicate that disintegration of the virions occurs in the cytoplasm and the L1/L2 proteins migrate to the nucleus via their nuclear localization signals.

Animals↗
PubMed1995

Sequences required for the nuclear targeting and accumulation of human papillomavirus type 6B L2 protein.

The L2 protein of the human papillomaviruses is a minor structural protein and is not necessary for the major L1 protein to assemble into capsids. However L2 protein binds DNA and enhances the efficiency of HPV capsid assembly, suggesting an important role in the production of infectious papillomaviruses. L2 accumulates rapidly in the nucleus after synthesis in the cytoplasm. To identify L2 sequences responsible for nuclear targeting and accumulation, full-length HPV6bL2 protein and L2 proteins containing sequence deletions were expressed in CV-1 cells, using recombinant vaccinia viruses. beta gal protein fused to C-terminal and N-terminal L2 sequences were localized in the nucleus and demonstrated that both the C-terminal putative nuclear localization signal (NLS) and N-terminal DNA binding sequences of the L2 protein, which are rich in arginine and lysine, are functional in targeting proteins into the nucleus. L2 mutants lacking amino acids (aa 286-306) do not accumulate in nucleus even when the C-terminal NLS and N-terminal DNA binding sequences are intact. Accumulation in the nucleus of L2 protein lacking aa 286-306 could be also achieved by increasing the L2 protein size via insertion of a portion of L1 protein. Amino acid sequence alignment of L2 proteins from sequenced papillomaviruses showed that sequences in this region are relatively conserved. Our results indicate that in the L2 protein, the nuclear targeting and accumulation are controlled by two different sequences and the rapid nuclear translocation and accumulation may play an important role in papillomavirus life cycle.

Amino Acid Sequence↗
PubMed1995

Lipopolysaccharide stimulates the tyrosine phosphorylation of mitogen-activated protein kinases p44, p42, and p41 in vascular endothelial cells in a soluble CD14-dependent manner. Role of protein tyrosine phosphorylation in lipopolysaccharide-induced stimulation of endothelial cells.

Vascular endothelial cell (EC) injury or activation by LPS plays a critical role in the pathogenesis of Gram-negative meningitis and endotoxic shock. EC do not express membrane CD14, but respond to LPS in a soluble CD14-dependent manner. The signal transduction mechanisms involved in LPS-induced EC responses are largely unknown. We used bovine and human brain microvessel EC (BBMEC, and HBMEC) to study LPS-induced protein tyrosine phosphorylation. LPS rapidly induced the tyrosine phosphorylation of several proteins in BBMEC and HBMEC, which was detectable by 5 to 15 min, reached a maximum by 30 min, and declined by 60 to 90 min. The increase in tyrosine phosphorylation was apparent following stimulation with LPS at 0.1 ng/ml and was dose dependent up to 100 ng/ml. Similar changes in tyrosine phosphorylation were induced by smooth and rough LPS as well as lipid A, but not by the inactive lipid A analogue, Rhodopseudomonas sphaeroides diphosphoryl lipid A. Pretreatment of EC with the tyrosine kinase inhibitor, herbimycin A, inhibited LPS-stimulated protein tyrosine phosphorylation and LPS-mediated lactic dehydrogenase release from BBMEC and IL-6 release from HBMEC in a dose-dependent manner. Three proteins with apparent m.w. of 44, 42, and 41 kDa were predominant among the LPS-induced tyrosine phosphoproteins, and they were identified as mitogen-activated protein kinase isoforms ERK1, ERK2, and p38, respectively. LPS-induced protein tyrosine phosphorylation in HBMEC and BBMEC was soluble CD14 dependent, since pretreatment of these cells with anti-hCD14 mAb inhibited the LPS-induced tyrosine phosphorylation of p44, p42, and p41. Additionally, LPS induced a mobility shift in p44 and p42 mitogen-activated protein kinase isozymes, which was inhibited by herbimycin A pretreatment of the EC. These findings demonstrate for the first time that increased protein tyrosine phosphorylation and activation of mitogen-activated protein kinases occur rapidly after LPS stimulation of EC in the presence of soluble CD14. Our data also suggest that a herbimycin-sensitive step, presumably a tyrosine kinase, is involved in mediating LPS-induced human EC activation and IL-6 secretion.

Amino Acid Sequence↗
PubMed1995

Structure, organization and expression of the metallothionein gene family in Arabidopsis.

Metallothioneins (MTs) are cysteine-rich proteins required for heavy metal tolerance in animals and fungi. Recent results indicate that plants also possess functional metallothionein genes. Here we report the cloning and characterization of five metallothionein genes from Arabidopsis thaliana. The position of the single intron in each gene is conserved. The proteins encoded by these genes can be divided into two groups (MT1 and MT2) based on the presence or absence of a central domain separating two cysteine-rich domains. Four of the MT genes (MT1a, MT1c, MT2a and MT2b) are transcribed in Arabidopsis. Several lines of evidence suggest that the fifth gene, MT1b, is inactive. There is differential regulation of the MT gene family. MT1 mRNA is expressed highly in roots, moderately in leaves and is barely detected in inflorescences and siliques. MT2a and MT2b mRNAs are more abundant in leaves, inflorescences and in roots from mature plants, but are also detected in roots of young plants, and in siliques. MT2a mRNA is strongly induced in seedlings by CuSO4, whereas MT2b mRNA is relatively abundant in this tissue and levels increase only slightly upon exposure to copper. MT1a and MT1c are located within 2 kb of each other and have been mapped to chromosome I. MT1b and MT2b map to separate loci on chromosome V, and MT2a is located on chromosome III. The locations of these MT genes are different from that of CAD1, a gene involved in cadmium tolerance in Arabidopsis.

Amino Acid Sequence↗
PubMed1995

Features of MotA proton channel structure revealed by tryptophan-scanning mutagenesis.

The MotA protein of Escherichia coli is a component of the flagellar motors that functions in transmembrane proton conduction. Here, we report several features of MotA structure revealed by use of a mutagenesis-based approach. Single tryptophan residues were introduced at many positions within the four hydrophobic segments of MotA, and the effects on function were measured. Function was disrupted according to a periodic pattern that implies that the membrane-spanning segments are alpha-helices and that identifies the lipid-facing parts of each helix. The results support a hypothesis for MotA structure and mechanism in which water molecules form most of the proton-conducting pathway. The success of this approach in studying MotA suggests that it could be useful in structure-function studies of other integral membrane proteins.

Amino Acid Sequence↗
PubMed1995

Membrane topology of the MotA protein of Escherichia coli.

The MotA protein of Escherichia coli is a component of the flagella that functions together with the MotB protein in transmembrane proton conduction. It is an integral membrane protein, with four hydrophobic segments that might traverse the membrane and two short segments that are predicted to be in the periplasm. In a previous study of the accessibility of MotA to various proteases, evidence for periplasmic segments was not obtained, probably because they are small. Here, we report site-directed sulfhydryl labeling experiments which show that two segments of MotA are exposed on the periplasmic side of the membrane, while the rest of the protein is in the cytoplasm. These experiments establish that the main features of the suggested model for MotA topology are correct, furnishing a basis for more detailed structure-function studies of the MotA/MotB proton channel.

Bacterial Proteins↗
PubMed1995

Papillary serous carcinoma of the peritoneum in women. A clinicopathologic and immunohistochemical study.

BACKGROUND: Papillary serous carcinoma of the peritoneum (PSCP) is a primary peritoneal tumor in women that histologically resembles papillary serous carcinoma of the ovary (PSCO). Recognition of PSCP as an entity is controversial, as is the histogenesis, histopathologic differential diagnosis, and treatment. METHODS: Ten cases of PSCP retrieved from the pathology files of 4 hospitals in Kyoto and Nara, Japan, were studied clinicopathologically and immunohistochemically. RESULTS: Patient ages at presentation ranged from 40 to 74 years (median, 56 years). All patients were Asian (Japanese). None of the patients had a history of asbestos exposure. Most of the patients had abdominal swelling, ascites with positive cytology, and elevated serum CA125. At surgery, omental tumors with dissemination to the abdominal and pelvic peritoneum were found in all patients. The histology was similar to that of Grade 2 to 3 PSCO. Immunohistochemical studies using a panel of monoclonal antibodies against carbohydrates showed that Lewis Y is a good marker, in addition to S-100, placental alkaline phosphatase, CA125, and CD15 for separating PSCP from malignant mesothelioma (MM). With cytoreductive surgery and cisplatin-based combination chemotherapy and in some cases adoptive immunotherapy and radiation, a median survival of 27 months and a 5-year survival rate of 27% were attained. One patient with Grade 3 tumor has survived for more than 6 years after surgery. CONCLUSIONS: (1) Papillary serous carcinoma of the peritoneum is a definite clinicopathologic entity; (2) immunohistochemistry is a useful tool for distinguishing PSCP from MM; (3) cytoreductive surgery and cisplatin-based combination chemotherapy with other adjunct therapies such as immunotherapy and radiation may improve patient survival in PSCP.

Adult↗
PubMed1995

Tryptophan-scanning mutagenesis of MotB, an integral membrane protein essential for flagellar rotation in Escherichia coli.

The MotB protein of Escherichia coli is an essential component of the flagella that functions together with the MotA protein in transmembrane proton conduction. MotB has a single hydrophobic segment that spans the membrane. In order to determine which parts of the membrane-spanning segment can tolerate the introduction of a large, hydrophobic side chain, single Trp residues were substituted into many consecutive positions in the segment and the effects on function were measured. Trp residues were tolerated at positions near the periplasmic end of the MotB segment but not at positions near the cytoplasmic end. These results are different from what was seen in a similar mutational study of MotA, in that protein Trp residues were tolerated at positions that would be clustered together on one face of each hydrophobic segment if they are alpha-helices [Sharp, L. L., Zhou, J., & Blair, D. F. (1995) Proc. Natl. Acad. Sci. U.S.A. (in press)]. Those results suggested that the membrane-spanning segments of MotA are alpha-helices arranged in a bundle so that each has a face directed toward the lipid. The contrasting results seen with MotB indicate that its relationship to neighboring protein segments is different. Double-Trp substitutions, one each in MotA and MotB, also were studied. Many double substitutions had strongly synergistic effects which imply that the membrane segments of these proteins interact. (ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Proteolysis prevents in vivo chimeric fusion protein import into yeast mitochondria. Cytosolic cleavage and subcellular distribution.

The in vivo import of liver mitochondrial aldehyde dehydrogenase was investigated in yeast by constructing fusion proteins between its leader sequence and beta-galactosidase. Only 7% of the protein was imported. If 21 or 71 amino acids from the mature portion of aldehyde dehydrogenase were included in the construct, 40% was imported. The protein remaining in cytosol was sequenced. When the leader was fused directly to beta-galactosidase, the first 7 residues of the leader were missing. When 21 residues of mature aldehyde dehydrogenase were included, the entire leader plus 6 residues of the mature portion were missing; if 71 residues of mature aldehyde dehydrogenase were included, the first residue found corresponds to the 66th residue of the mature portion. When the leader was fused directly to beta-galactosidase, no processing of the imported protein occurred, and the N-terminal amino acid was blocked, presumably by acetylation. If the 21-amino acid insert was included, processing occurred. A modified leader sequence lacking the three-amino acid linker (RGP) was imported but not processed, just as we found in vitro (Thornton, K., Wang, Y., Weiner, H., and Gorenstein, D.G. (1993) J. Biol. Chem. 268, 19906-19914). The less than 100% import of pre-aldehyde dehydrogenase was due to the action of a post-translational protease attack which prevented import by destroying the leader peptide segment.

Aldehyde Dehydrogenase↗
PubMed1995

Signal transduction alterations in peripheral nerves from streptozotocin-induced diabetic rats.

We have previously determined the presence of muscarinic receptors and the expression of several G proteins in homogenates and myelin fractions from rat sciatic nerves. In the present study we investigated whether changes in several signal transduction pathways in peripheral nerves might be responsible for some of the biochemical abnormalities (e.g., phosphoinositide metabolism) present in sciatic nerves from streptozotocin-induced diabetic rats. Sciatic nerves from 5 week diabetic rats that were prelabelled with [3H]-myo-inositol displayed a significant increase in the basal release of inositol mono- and bis-phosphate, while carbamylcholine-stimulated release was significantly smaller. Basal- and forskolin-stimulated adenylyl cyclase activity was significantly decreased in sciatic nerve homogenates from diabetic animals. However, we were unable to detect any significant differences in the levels of cAMP in intact nerves or in nerve segments that were incubated in the presence or absence of forskolin. ADP-ribosylation experiments showed that in sciatic nerves from experimentally diabetic rats there was a significant increase in the ADP-ribosylation catalyzed by cholera and pertussis toxins. Measurements of the levels of alpha-subunits of G proteins revealed that the expression of Gq/11 alpha, Gs alpha, and Gi-3 alpha was increased by 30 to 50%. These results indicate that during the course of experimental diabetes, peripheral nerves exhibit an abnormal production of inositol phosphates and cAMP, together with an abnormal expression and/or function of G proteins. One of the consequences of such alterations is the diminished release of inositol phosphates triggered by muscarinic agonists in diabetic sciatic nerves.

Adenylyl Cyclases↗
PubMed1995

Monoamines in the parabrachial nucleus of the cardiomyopathic hamster.

The development of dystrophic cardiac muscle is related to increases in sympathetic nervous system activity but little is known regarding possible central neural mechanisms that may be involved in cardiomyopathy. The inbred cardiomyopathic hamster is an animal model for studying the development and mechanisms of necrosis in cardiac muscle which resemble non-vascular myocardial diseases of man. Because monoamines are known to play a major role in central regulation of the cardiovascular system, we compared the distribution and density of tyrosine hydroxylase (TH) and 5-hydroxytryptamine (5-HT) immunostaining in the brains of cardiomyopathic hamsters (strain CHF-146), a related strain (CHF-148) of non-cardiomyopathic albino hamsters, and golden Syrian hamsters for possible differences in neurochemical organization. At the time of sacrifice, the cardiomyopathic hamsters exhibit small, calcified lesions on the surface of the ventricular cardiac muscle (early necrotic phase). Brain sections from each group were processed identically and simultaneously. The results show that there were significant differences among strains in the parabrachial nucleus with respect to the two neurochemicals examined. In golden Syrian and albino hamsters, TH and 5-HT immunoreactive axons were lightly-to-moderately stained in the lateral parabrachial nucleus. In the cardiomyopathic hamster, there were significantly more densely stained TH and 5-HT immunoreactive axons in the lateral parabrachial nucleus, in particular the inner part of the external lateral subnucleus. Because the lateral parabrachial nucleus, including the external lateral subnucleus, is known to be involved in regulation of the cardiovascular system, the differential distribution of TH and 5-HT in the parabrachial nucleus of cardiomyopathic hamsters in comparison to normal hamsters suggests that the parabrachial nucleus could be involved in sympathetic mechanisms related to the development of necrosis in cardiac muscle of the cardiomyopathic hamster.

Animals↗
PubMed1995

Cryogenic spinal cord injury induces astrocytic gene expression of insulin-like growth factor I and insulin-like growth factor binding protein 2 during myelin regeneration.

To study injury-induced astrocytic responses associated with regrowth of axons and regeneration of myelin, the method of Collins and colleagues was used to make focal cryogenic lesions in spinal cords of adult rats (Collins et al.: J Neuropathol Exp Neurol 45: 742-757, 1986). The duration of cryogenic injury (CI), the size of the cryode, and its temperature were chosen to destroy all myelin sheaths and axons without producing cavities or hemorrhages. Messenger RNA and peptide distributions of insulin-like growth factor I (IGF-I), IGF-I receptor (IGFR-I), IGF binding protein 2 (IGFBP-2), glial fibrillary acidic protein (GFAP), and myelin basic protein (MBP) were studied 3-56 days after CI by in situ hybridization and immunocytochemistry. At 3 days, vimentin-positive, GFAP-negative astrocyte-like cells in the lesion expressed IGF-I mRNA and peptide and 7 days after CI, both were expressed by typical GFAP-positive, hypertrophic astrocytes, many of which also were vimentin-positive. Levels of IGF-I, IGFBP-2, and GFAP mRNA and peptide were higher in lesion astrocytes after 14 days. They attained maximum levels at 21-28 days before declining to near control levels at 56 days. Decreasing relative levels of oligodendroglial MBP mRNA were found in and around lesions 7-14 days after CI; subsequently, rising levels accompanied remyelination. At 28 and 56 days after CI, some transferrin-positive, oligodendroglia-like cells also were immunostained by anti-IGFR-I. Our findings suggest that early astrocytic production of IGF-I and IGFBP-2 may be involved in the myelin regeneration which occurs in this model of spinal cord injury.

Animals↗
PubMed1995

Contact-dependent endothelial class II HLA gene activation induced by NK cells is mediated by IFN-gamma-dependent and -independent mechanisms.

NK lymphocytes adhere avidly to allogeneic endothelial cells (ECs) and induce their membrane expression of MHC class II Ags in vitro. Endothelial class II expression augments EC-driven CD4+ T cell proliferation in vitro, and may amplify T cell recruitment and clonal expansion in vivo. Using an ex vivo lymphocyte-skin organ coculture model, NK cells could be found lining and inducing class II HLA on microvessel endothelium. Using neutralizing anti-IFN-gamma and anti-IFN-gamma receptor Abs, a spectrum of IFN-gamma dependence was observed for NK-mediated EC HLA-DR induction at the membrane and transcriptional levels, from negligible to moderate. Trans-well experiments displayed that direct NK-EC contact is required, and Ab inhibition studies indicated that the beta 2 integrin-ICAM-1 pathway(s) is critical in the generation of these responses. The use of HLA-DR alpha promoter constructs in transient transfection assays demonstrated that the highly conserved X and S transcription boxes are required in both IFN-gamma- and NK-mediated gene activation. As expected, because of the receptor species specificity, human IFN-gamma did not induce HLA-DR alpha promoter constructs transfected in Chinese hamster ovary cells, whereas NK cells did. Taken together, these results indicate that human allogeneic NK lymphocytes induce EC class II HLA gene activation and membrane expression in an adhesion-dependent, IFN-gamma-independent fashion and suggest that, in concert with any IFN-gamma-dependent component, this induction could represent an efficient mode of endothelial activation and immune amplification in vivo.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1995

Modulation of cloned neuronal calcium channels through membrane-delimited pathway.

Modulation of voltage-gated Ca2+ channels by the receptor coupled GTP-binding proteins (G-proteins) is essential for controlling secretion and muscle contraction. We have expressed cloned Ca2+ channels in dysgenic myotubes to study G-protein modulation through the membrane-delimited pathway. The results obtained by the expression of alpha 1B channels and mutant channels of alpha 1B suggest that the two effects observed in G-protein modulated N-type channels (depression of current and slowing of activation) are through two independent mechanisms. In addition, neither the region linking repeat II and III nor carboxy-terminal region, which were demonstrated in L-type channels to determine some of their specific functions, are directly involved in G-protein modulation. The results obtained by the expression of the alpha 1A channel suggest that this channel is modulated through a novel membrane-delimited pathway that may not involve G-protein activation.

Animals↗