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Y J Zhou

Publications and source records attributed to Y J Zhou.

At least 19 recordsLinked to original sources
PubMed2007

Roles of mitogen-activated protein kinase pathways during Escherichia coli-induced apoptosis in U937 cells.

Escherichia coli (E. coli) infections play an important and growing role in the clinic. In the present study, we investigated the involvement of members of the mitogen-activated protein kinase (MAPK) superfamily, including extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase (JNK) and p38 MAPK, and caspase-3 and 9 activity in E. coli-induced apoptosis in human U937 cells. We found that E. coli induces apoptosis in U937 cell lines in a dose- and time-dependent manner, p38 MAPK and JNK were activated after 10 min of infection with E. coli. In contrast, ERK1/2 was down-regulated in a time-dependent manner. The levels of total (phosphorylation state-independent) p38 MAPK, JNK and ERK1/2 did not change in E. coli-infected U937 cells at all times examined. Moreover, exposure of U937 cells to E. coli led to caspase-3 and 9 activity. For the evaluation of the role of MAPKs, PD98059, SB203580 and SP600125 were used as MAPKs inhibitors for ERK1/2, p38 MAPK and JNK. Inhibition of ERK1/2 with PD98059 caused further enhancement in apoptosis and caspase-3 and 9 activity, while a selective p38 MAPK inhibitor, SB203580 and JNK inhibitor, SP600125 significantly inhibited E. coli-induced apoptosis and caspase-3 and 9 activity in U937 cells. The results were further confirmed by the observation that the caspase inhibitors Z-DEVD-FMK and Z-LEHD-FMK blocked E. coli-induced U937 apoptosis. Taken together, we have shown that E. coli increase p38 MAPK and JNK and decrease ERK1/2 phosphorylation and increase caspase-3 and 9 activity in U937 cells.

Apoptosis↗
PubMed2001

Nonsymbiotic hemoglobins in rice are synthesized during germination and in differentiating cell types.

Nonsymbiotic hemoglobins (ns-Hbs) previously have been found in monocots and dicots; however, very little is known about the tissue and cell type localization as well as the physiological function(s) of these oxygen-binding proteins. We report the immunodetection and immunolocalization of ns-Hbs in rice (Oryza sativa L.) by Western blotting and in situ confocal laser scanning techniques. Ns-Hbs were detected in soluble extracts of different tissues from the developing rice seedling by immunoblotting. Levels of ns-Hbs increased in the germinating seed for the first six days following imbibition and remained relatively constant thereafter. In contrast, ns-Hb levels decreased during leaf maturation. Roots and mesocotyls contained detectable, but low levels of ns-Hbs. Split-seed experiments revealed that ns-Hbs are synthesized de novo during seed germination and are expressed in the absence of any signal originating from the embryo. Immunolocalization of ns-Hbs by confocal microscopy indicated the presence of ns-Hbs primarily in differentiated and differentiating cell types of the developing seedling, such as the aleurone, scutellum, root cap cells, sclerenchyma, and tracheary elements. To our knowledge, this is the first report of the specific cellular localization of these proteins during seedling development.

Blotting, Western↗
PubMed2001

Signaling by type I and II cytokine receptors: ten years after.

Discovered during the past ten years, Janus kinases and signal transducers and activators of transcription have emerged as critical elements in cytokine signaling and immunoregulation. Recently, knockout mice for all the members of these families have been generated, with remarkably specific outcomes. Equally exciting is the discovery of a new class of inhibitors, the suppressor of cytokine signaling family. The phenotypes of mice deficient in these molecules are also striking, underscoring the importance of negative regulation in cytokine signaling.

Animals↗
PubMed2001

Unexpected effects of FERM domain mutations on catalytic activity of Jak3: structural implication for Janus kinases.

Janus kinases comprise carboxyterminal kinase, pseudokinase, SH2-like, and N-terminal FERM domains. We identified three patient-derived mutations in the FERM domain of Jak3 and investigated the functional consequences of these mutations. These mutations inhibited receptor binding and also abrogated kinase activity, suggesting interactions between the FERM and kinase domains. In fact, the domains were found to physically associate, and coexpression of the FERM domain enhanced activity of the isolated kinase domain. Conversely, staurosporine, which alters kinase domain structure, disrupted receptor binding, even though the catalytic activity of Jak3 is dispensable for receptor binding. Thus, the Jak FERM domain appears to have two critical functions: receptor interaction and maintenance of kinase integrity.

Adenosine Triphosphate↗
PubMed2001

[Properties of KATP channels in hippocampal CA1 pyramidal neurons from adult rats].

Properties of KATP channels in acutely dissociated hippocampal CA1 pyramidal neurons of adult rats were studied with inside-out patch-clamp technique. With symmetrical 140 mmol/L K+ on both sides of the excised membrane, the single-channel conductance was approximately 63 pS and the reversal potential was 1.71 mV. These channels had a weak inward rectifying property. Channels' openings interrupted by shorter closed intervals were more frequently observed at negative holding potential than at positive holding potential. However, noticeable voltage dependence was not found in channel open probability. ATP applied at the cytosolic side inhibited channel activity in a concentration-dependent manner with an IC50 of 0.1 mmol/L. Sulphonyluren tolbutamide (1 mmol/L), a specific KATP channel blocker, added to the bath completely suppressed the channel activity, while diazoxide (1 mmol/L), a KATP channel opener, had no apparent effect.

Adenosine Triphosphate↗
PubMed2001

[Synthesis, preliminary antigastrelcosis activity and the protective effect on acute liver injury of zinc chlorin E4].

AIM: To study the synthesis of zinc chlorin e4(1), its experimental antigastrelcosis activity as well as the protection against acute liver injuries. METHODS: Chlorin e6(3) was prepared through acidic and alkaline oxidative degradation using silkworm excrement crude chlorophyll extracts as starting material. Compound 1 was synthesized via Zn(OAc)2 complex action with Chlorin e4(2) which was prepared by refluxing 3 in pyridine. Gastric ulcers were induced by abdominal injection of 0.2% indomethacin at 20 mg.kg-1 in rats. The ulcer indexes and ulcer numbers in gastric mucosa were determined. Acute liver injuries were induced by abdominal injection of 0.3% thioacetamide (TAA) or 0.3% CCl4 at 20 mg.kg-1 in mice, and activities of SGPT in mice were determined. RESULTS: Compound 1 is previously unknown. Compared with control group, abdominal administration of 1 at 100 mg.kg-1 reduced significantly the gastric ulcer index (P < 0.001) and the number of ulcer (P < 0.001) induced by indomethacin in rats. Abdominal administration of 1 at 100 mg.kg-1 x 3 exhibited marked inhibitory effects on elevated activities of SGPT induced by TAA (P < 0.02) or CCl4(P < 0.01) in mice. CONCLUSION: These results show that 1 has significant protective effect against indomethacin-induced gastric lesion in rats and TAA or CCl4 induced acute liver injuries in mice. It is suggested that 1 may be a promising new drug candidate for antigastrelcosis and liver injury protection.

Animals↗
PubMed2000

The docking molecule gab2 is induced by lymphocyte activation and is involved in signaling by interleukin-2 and interleukin-15 but not other common gamma chain-using cytokines.

Interleukin (IL)-2, a critical cytokine with indispensable functions in regulating lymphoid homeostasis, induces the activation of several biochemical pathways. Precisely how these pathways are linked and how they relate to the biological action of IL-2 is incompletely understood. We previously identified SHP-2 (Src homology 2 domain containing phosphatase 2) as an important intermediate in IL-2-dependent MAPK activation and showed its association with a 98-kDa phosphoprotein in response to IL-2. Here, we demonstrate that Gab2, a recently identified adapter molecule, is the major SHP-2 and phosphatidylinositol 3'-kinase-associated 98-kDa protein in normal, IL-2-activated lymphocytes. We further demonstrate that phosphorylation of both Gab2 and SHP-2 is largely dependent upon tyrosine 338 of the IL-2 receptor beta chain. Gab2 can be a substrate of all the three major classes of non-receptor tyrosine kinases associated with the IL-2R, but in terms of IL-2 signaling, JAK3 but not Lck or Syk is essential for Gab2 phosphorylation. We also demonstrate that only IL-2 and IL-15, but not other gammac cytokines induce Gab2 phosphorylation; the ability to phosphorylate Gab2 correlates with Shc phosphorylation and ERK1/ERK2 activation. Finally, we also show that Gab2 levels are regulated by T cell activation, and resting T cells express little Gab2. Therefore, up-regulation and activation of Gab2 may be important in linking the IL-2 receptor to activation of MAPK and may be an important means of achieving specificity in cytokine signaling.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Hierarchy of protein tyrosine kinases in interleukin-2 (IL-2) signaling: activation of syk depends on Jak3; however, neither Syk nor Lck is required for IL-2-mediated STAT activation.

Interleukin-2 (IL-2) activates several different families of tyrosine kinases, but precisely how these kinases interact is not completely understood. We therefore investigated the functional relationships among Jak3, Lck, and Syk in IL-2 signaling. We first observed that in the absence of Jak3, both Lck and Syk had the capacity to phosphorylate Stat3 and Stat5a. However, neither supported IL-2-induced STAT activation, nor did dominant negative alleles of these kinases inhibit. Moreover, pharmacological abrogation of Lck activity did not inhibit IL-2-mediated phosphorylation of Jak3 and Stat5a. Importantly, ligand-dependent Syk activation was dependent on the presence of catalytically active Jak3, whereas Lck activation was not. Interestingly, Syk functioned as a direct substrate of Jak1 but not Jak3. Additionally, Jak3 phosphorylated Jak1, whereas the reverse was not the case. Taken together, our data support a model in which Lck functions in parallel with Jak3, while Syk functions as a downstream element of Jaks in IL-2 signaling. Jak3 may regulate Syk catalytic activity indirectly via Jak1. However, IL-2-mediated Jak3/Stat activation is not dependent on Lck or Syk. While the essential roles of Jak1 and Jak3 in signaling by gammac-utilizing cytokines are clear, it will be important to dissect the exact contributions of Lck and Syk in mediating the effects of IL-2 and related cytokines.

Animals↗
PubMed2000

Complex effects of naturally occurring mutations in the JAK3 pseudokinase domain: evidence for interactions between the kinase and pseudokinase domains.

The structure of Janus kinases (JAKs) is unique among protein tyrosine kinases in having tandem, nonidentical kinase and pseudokinase domains. Despite its conservation in evolution, however, the function of the pseudokinase domain remains poorly understood. Lack of JAK3 expression results in severe combined immunodeficiency (SCID). In this study, we analyze two SCID patients with mutations in the JAK3 pseudokinase domain, which allows for protein expression but disrupts the regulation of the kinase activity. Specifically, these mutant forms of JAK3 had undetectable kinase activity in vitro but were hyperphosphorylated both in patients' Epstein-Barr virus-transformed B cells and when overexpressed in COS7 cells. Moreover, reconstitution of cells with these mutants demonstrated that, although they were constitutively phosphorylated basally, they were unable to transmit cytokine-dependent signals. Further analysis showed that the isolated catalytic domain of JAK3 was functional whereas either the addition of the pseudokinase domain or its deletion from the full-length molecule reduced catalytic activity. Through coimmunoprecipitation of the isolated pseudokinase domain with the isolated catalytic domain, we provide the first evidence that these two domains interact. Furthermore, whereas the wild-type pseudokinase domain modestly inhibited kinase domain-mediated STAT5 phosphorylation, the patient-derived mutants markedly inhibited this phosphorylation. We thus conclude that the JAK3 pseudokinase domain is essential for JAK3 function by regulating its catalytic activity and autophosphorylation. We propose a model in which this occurs via intramolecular interaction with the kinase domain and that increased inhibition of kinase activity by the pseudokinase domain likely contributes to the disease pathogenesis in these two patients.

Amino Acid Sequence↗
PubMed2000

[On-line measurement of oxygen uptake rate in the cultivation of Vero cells using the dynamic method].

The oxygen uptake rate(OUR) during the cultivation of Vero cells in 1.5 L CelliGen bioreactor was on-line determined using the dynamic method. The results showed that the cell growth and metabolic state during the exponential growth phase was lineally related to the OUR. This implies that the on-line measurement of OUR can be used to promptly monitor the physiological state of cultured cells and to efficiently avoid contamination because of frequent sampling in the large-scale cultivation of mammalian cells.

Animals↗
PubMed1999

Requirement for a negative charge at threonine 60 of the FcRgamma for complete activation of Syk.

Aggregation of FcepsilonRI on mast cells results in the phosphorylation of the FcepsilonRIgamma chain on tyrosine and threonine residues within the immunoreceptor tyrosine-based activation motif. In the present study we sought to identify the site of threonine phosphorylation in FcepsilonRIgamma and investigate its functional importance. We found that threonine 60 was phosphorylated in vitro and in vivo. Expression of a mutated FcepsilonRIgamma (T60A), in either FcepsilonRIgamma-deficient or gamma-null mast cells, resulted in a delay of FcepsilonRI endocytosis, inhibition of TNF-alpha mRNA production, and inhibition of degranulation but did not affect FcepsilonRI-induced cell adhesion. Tyrosine phosphorylation of the T60A mutant gamma chain was normal, but Syk phosphorylation was dramatically reduced in these transfectants. This correlated with reduced co-immunoprecipitation of FcepsilonRIgamma with Syk. Substitution of an aspartic residue for threonine 60 of the FcepsilonRIgamma reconstituted complete activation of Syk and co-immunoprecipitation of FcepsilonRIgamma with Syk. We conclude that the negative charge provided by phosphorylation of threonine 60 of the FcepsilonRIgamma is required for the appropriate interaction and activation of Syk. This is a likely requirement for immunoreceptor tyrosine-based activation motifs involved in Syk activation.

Amino Acid Sequence↗
PubMed1999

Janus kinases and their role in growth and disease.

Janus kinases (JAK) play a crucial role in the initial steps of cytokine signaling. Each of the four members (JAK1, JAK2, JAK3, TYK2) of this non-receptor tyrosine kinase family is indispensable for the effects of distinct cytokines. Moreover, recent reports have added to our knowledge on their highly specific functions: JAK3 knockout mice and JAK3 deficient patients cannot signal through the interleukin-2,4,7,9, or 15 receptors and suffer from severe combined immunodeficiency (SCID). JAK1 and JAK2 knockout mice do not survive, their cells again showing distinct patterns of cytokine signaling deficits. At the other end of the spectrum, JAK fusion proteins have been shown to play a role in leukemias. In addition, a new class of JAK-specific inhibitors was described by several groups, the CIS/SOCS/Jab family. This review on the rapidly growing field focuses on JAK function and regulation, and on their emerging role in development and human disease.

Animals↗
PubMed1998

[Effects of Gu Chi paste on PGE(2) in periodontitis tissues of guinea pigs]

OBJECTIVE: Study the effects of Gu Chi paste on PGE(2) in gingiva and alveolar bone and its mechanism to treating periodontitis. METHODS: Periodontitis were formed with silk thread suture and high sugar diet,fed guinea pigs on Gu Chi paste and indomethacin.The prostaglandin E(2)(PGE(2)) in gingiva and alveolar bone were measured with radioimmunoassay (RIA). RESULTS: The Gingival Index(GI) and Pocket Deep(PD) of group Periodontitis (PE) were bigger than group Normal(N),the alveolar bone absorbed more severe,the PGE(2) level in gingiva and alveolar bone in PE was higherthan that in N.The GI and PD of group Gu Chi paste(Gu) were lower than that of PE,its alveolar bone absorbed more slight.There were more significant difference of PGE(2) in alveolar bone between Gu and group indomethacin(IND).The PGE(2) level of Gu in gingiva were similar as that of IND. CONCUSION: Gu Chi paste can inhibite the formation of experimental periodontitis and the contents of PGE(2) in gingiva and alveolar bone,and the effect on PGE(2) in alveolar was more severe. The mechanism of Gu Chi paste to periodontitis has inhibitory effects on PGE(2) in gingiva and alveolar bone.

Journal Article↗
PubMed1997

Distinct tyrosine phosphorylation sites in JAK3 kinase domain positively and negatively regulate its enzymatic activity.

Cytokines are critically important for the growth and development of a variety of cells. Janus kinases (JAKs) associate with cytokine receptors and are essential for transmitting downstream cytokine signals. However, the regulation of the enzymatic activity of the JAKs is not well understood. Here, we investigated the role of tyrosine phosphorylation of JAK3 in regulating its kinase activity by analyzing mutations of tyrosine residues within the putative activation loop of the kinase domain. Specifically, tyrosine residues 980 and 981 of JAK3 were mutated to phenylalanine individually or doubly. We found that JAK3 is autophosphorylated on multiple sites including Y980 and Y981. Compared with the activity of wild-type (WT) JAK3, mutant Y980F demonstrated markedly decreased kinase activity, and optimal phosphorylation of JAK3 on other sites was dependent on Y980 phosphorylation. The mutant Y980F also exhibited reduced phosphorylation of its substrates, gammac and STAT5A. In contrast, mutant Y981F had greatly increased kinase activity, whereas the double mutant, YY980/981FF, had intermediate activity. These results indicate that Y980 positively regulates JAK3 kinase activity whereas Y981 negatively regulates JAK3 kinase activity. These observations in JAK3 are similar to the findings in the kinase that is closely related to the JAK family, ZAP-70; mutations of tyrosine residues within the putative activation loop of ZAP-70 also have opposing actions. Thus, it will be important to determine whether this feature of regulation is unique to JAK3 or if it is also a feature of other JAKs. Given the importance of JAKs and particularly JAK3, it will be critical to fully dissect the positive and negative regulatory function of these and other tyrosine residues in the control of kinase activity and hence cytokine signaling.

Animals↗
PubMed1997

[Synthesis and antifungal activities of 1-(2-[(substituted-phenyl) methyl]thio)-2-(2,4-difluorophenyl)ethyl-1H-1,2,4-triazoles].

Twenty-one 1-[2-[[(substituted-phenyl) methyl] thio]-2-(2, 4-difluorophenyl) ethyl]-1H-1,2,4-triazoles were synthesized and 19 compounds are reported for the first time. Results of biological tests in vitro showed that the antifungal activities of all title compounds were better than or comparable to the activities of fluconazole. The antifungal activities of compounds 1-7 and 11-17 were better than or comparable to the activities of sulconazole. Compounds 1, 2 and 5 were 512 times more active than sulconazole against epidermophyton floccosum; compound 5 was 32 times more active against Candida albicans, compound 2 was 32 times more active against Sporotrichum schenckii; compounds 2 and 14 were shown to be 64 and 32 times more active against Cryptococcus neoformans; compounds 1 and 5 were 16 times more active against Aspergillus fumigatus.

Antifungal Agents↗
PubMed1997

[Comparative molecular field analysis (CoMFA) of allylamine antimycotics].

Active analog approach has been applied to determine the pharmacophoric conformations of the allylamine antimycotics. Comparative molecular field analysis (CoMFA) has been used to establish 3D-QSAR of 48 allylamine antimycotics against six common human pathogenic fungi. Two different alignment rules were compared in the meantime. Five new synthetic compounds have been successfully employed to examine the predictive abilities of the CoMFA models against Trichophyton mentagrophytes and Aspergillus fumigatus.

Allylamine↗