Biomedical subjects

H Shao

Publications and source records attributed to H Shao.

At least 19 recordsLinked to original sources

PubMed2001

Identification and characterization of cis elements in the STAT3 gene regulating STAT3 alpha and STAT3 beta messenger RNA splicing.

Signal transducer and activator of transcription 3 (STAT3) is an oncogene and a critical regulator of multiple cell-fate decisions, including myeloid cell differentiation. Two isoforms of STAT3 have been identified: alpha (p92) and beta (p83). These differ structurally in their C-terminal transactivation domains, resulting in distinct functional activities. The cis genetic elements that regulate the ratio of alpha to beta messenger RNA (mRNA) are unknown. In this study, cloning, sequencing, and splicing analysis of the human and murine STAT3 genes revealed a highly conserved 5' donor site for generation of both alpha and beta mRNA and distinct branch-point sequences, polypyrimidine tracts, and 3' acceptor sites (ASs) for each. The beta 3' AS was found to be located 50 nucleotides downstream of the alpha 3' AS in exon 23. Two additional cryptic 3' ASs (delta and epsilon) were also identified. Thus, we identified for the first time the cis regulatory sequences responsible for generation of STAT3 alpha and STAT3 beta mRNA.

Animals↗

PubMed2001

Melatonin reverses the profibrillogenic activity of apolipoprotein E4 on the Alzheimer amyloid Abeta peptide.

Inheritance of apoE4 is a strong risk factor for the development of late-onset sporadic Alzheimer's disease (AD). Several lines of evidence suggest that apoE4 binds to the Alzheimer Abeta protein and, under certain experimental conditions, promotes formation of beta-sheet structures and amyloid fibrils. Deposition of amyloid fibrils is a critical step in the development of AD. We report here that addition of melatonin to Abeta in the presence of apoE resulted in a potent isoform-specific inhibition of fibril formation, the extent of which was far greater than that of the inhibition produced by melatonin alone. This effect was structure-dependent and unrelated to the antioxidant properties of melatonin, since it could be reproduced neither with the structurally related indole N-acetyl-5-hydroxytryptamine nor with the antioxidants ascorbate, alpha-tocophenol, and PBN. The enhanced inhibitory effects of melatonin and apoE were lost when bovine serum albumin was substituted for apoE. In addition, Abeta in combination with apoE was highly neurotoxic (apoE4 > apoE3) to neuronal cells in culture, and this activity was also prevented by melatonin. These findings suggest that reductions in brain melatonin, which occur during aging, may contribute to a proamyloidogenic microenvironment in the aging brain.

Alzheimer Disease↗

PubMed2001

RERG is a novel ras-related, estrogen-regulated and growth-inhibitory gene in breast cancer.

Using microarray analysis, we identified a unique ras superfamily gene, termed RERG (ras-related and estrogen-regulated growth inhibitor), whose expression was decreased or lost in a significant percentage of primary human breast tumors that show a poor clinical prognosis. Importantly, high RERG expression correlated with expression of a set of genes that define a breast tumor subtype that is estrogen receptor-positive and associated with a slow rate of tumor cell proliferation and a favorable prognosis for these cancer patients. RERG mRNA expression was induced rapidly in MCF-7 cells stimulated by beta-estradiol and repressed by tamoxifen treatment. Like Ras, RERG protein exhibited intrinsic GDP/GTP binding and GTP hydrolysis activity. Unlike Ras proteins, RERG lacks a known recognition signal for COOH-terminal prenylation and was localized primarily in the cytoplasm. Expression of RERG protein in MCF-7 breast carcinoma cells resulted in a significant inhibition of both anchorage-dependent and anchorage-independent growth in vitro and inhibited tumor formation in nude mice. These features of RERG are strikingly different from most Ras superfamily GTP-binding pro-teins and suggest that the loss of RERG expression may contribute to breast tumorigenesis.

3T3 Cells↗

PubMed2001

Molten-globule structure and membrane binding of the N-terminal protease-resistant domain (63-193) of the steroidogenic acute regulatory protein (StAR).

The first step in steroidogenesis is the movement of cholesterol from the outer to inner mitochondrial membrane; this movement is facilitated by the steroidogenic acute regulatory protein (StAR). StAR has molten-globule properties at low pH and a protease-resistant N-terminal domain at pH 4 and pH 8 comprising residues 63-193. To explore the mechanism of action of StAR we investigated the structural properties of the bacterially expressed N-terminal domain (63-193 StAR) using CD, limited proteolysis and NMR. Far- and near-UV CD showed that the amount of secondary structure was greater at acidic than at neutral pH, but there was little tertiary structure at any pH. Unlike 63-193 StAR liberated from N-62 StAR by proteolysis, biosynthetic 63-193 StAR was no longer resistant to trypsin or proteinase K at pH 7, or to pepsin at pH 4. Addition of trifluoroethanol and SDS increased secondary structure at pH 7, and dodecylphosphocholine and CHAPS increased secondary structure at pH 2, pH 4 and pH 7. However, none of these conditions induced tertiary structure, as monitored by near-UV CD or NMR. Liposomes of phosphatidylcholine, phosphatidylserine and their mixture increased secondary structure of 63-193 StAR at pH 7, as monitored by far-UV CD, and stable protein-liposome complexes were identified by gel-permeation chromatography. These results provide further evidence that the N-terminal domain of StAR is a molten globule, and provide evidence that this conformation facilitates the interaction of the N-terminal domain of StAR with membranes. We suggest that this interaction is the key to understanding the mechanism of StAR's action.

Gene Products, env↗

PubMed2001

Nicotine and amyloid formation.

The major protein constituents of amyloid deposits in Alzheimer's disease (AD) are the 40-residue beta-amyloid (Abeta) (1-40) peptide and the 42-residue Abeta(1-42) peptide. The Abeta(1-42) is more pathogenic and produced in greater quantities in familial forms of AD. A major goal of research is to uncover a suitable inhibitor that either slows down or inhibits Abeta formation (beta-amyloidosis). During beta-amyloidosis, structural changes associated with the conversion of monomeric Abeta peptide building blocks into the aggregated fibrillar beta-sheet structures occur (alpha-helix-->beta-sheet or random, extended chain-->beta-sheet). In previous work, we and others established that nicotine, a major component of cigarette smoke, inhibits beta-amyloidosis of the Abeta(1-42), which may result from nicotine binding to the alpha-helical structure. These conclusions were based on solution nuclear magnetic resonance (NMR) spectroscopic studies with the nonnative 28-residue Abeta(1-28). This information suggests that, when administered therapeutically to AD patients, nicotine may not only affect cholinergic activation, but could also conceivably alter amyloid deposition. In this report, NMR studies were augmented with the naturally occurring Abeta(1-42), under conditions where the peptide folds into a predominantly alpha-helical or random, extended chain structure. The major result is that nicotine shows only modest binding to these conformations, indicating that the nicotine inhibition to beta-amyloidosis probably results from binding to a small, soluble beta-sheet aggregate that is NMR invisible.

Alzheimer Disease↗

PubMed2001

MsqTc3, a Tc3-like transposon in the yellow fever mosquito Aedes aegypti.

A novel transposon, MsqTc3-Aa, has been discovered in the yellow fever mosquito, Aedes aegypti. Evidence of its past mobility is presented. There are approximately 100 copies of MsqTc3-Aa in A. aegypti, eight of which have been isolated and sequenced. All sequenced copies are more than 99% identical to their consensus, indicating recent mobilization. The MsqTc3-Aa consensus contains imperfect terminal inverted repeats (TIRs) and an open reading frame (ORF) interrupted by an intron. Sequence, structural and phylogenetic analysis showed that MsqTc3-Aa is a distant relative of Tc3, an active transposon in Caenorhabditis elegans. These results may provide useful information for the current effort to control mosquito-borne diseases using genetic approaches.

Aedes↗

PubMed2001

Expanding the diversity of the IS630-Tc1-mariner superfamily: discovery of a unique DD37E transposon and reclassification of the DD37D and DD39D transposons.

A novel transposon named ITmD37E was discovered in a wide range of mosquito species. Sequence analysis of multiple copies in three Aedes species showed similar terminal inverted repeats and common putative TA target site duplications. The ITmD37E transposases contain a conserved DD37E catalytic motif, which is unique among reported transposons of the IS630-Tc1-mariner superfamily. Sequence comparisons and phylogenetic analyses suggest that ITmD37E forms a novel family distinct from the widely distributed Tc1 (DD34E), mariner (DD34D), and pogo (DDxD) families in the IS630-Tc1-mariner superfamily. The inclusion in the phylogenetic analysis of recently reported transposons and transposons uncovered in our database survey provided revisions to previous classifications and identified two additional families, ITmD37D and ITmD39D, which contain DD37D and DD39D motifs, respectively. The above expansion and reorganization may open the doors to the discovery of related transposons in a broad range of organisms and help illustrate the evolution and structure-function relationships among these distinct transposases in the IS630-Tc1-mariner superfamily. The presence of intact open reading frames and highly similar copies in some of the newly characterized transposons suggests recent transposition. Studies of these novel families may add to the limited repertoire of transgenesis and mutagenesis tools for a wide range of organisms, including the medically important mosquitoes.

Amino Acid Motifs↗

PubMed2001

Requirement of B7-mediated costimulation in the induction of experimental autoimmune anterior uveitis.

PURPOSE: To study the role of costimulatory signaling through the CD28-B7 interaction in experimental autoimmune anterior uveitis (EAAU). METHODS: Naive Lewis rats were immunized with insoluble melanin-associated antigen (MAA) derived from bovine iris and ciliary body. CTLA4-Fc, a recombinant protein comprised of the extracellular domain of human CTLA4 bound to mouse IgG2a Fc, was used to block the CD28-B7 interaction. A mutant version (CTLA4-Fc-mutant) was used as a control. The effect of CTLA4-Fc on the in vivo induction of disease with MAA was studied. Subsequently, the mechanism by which CTLA4-Fc blocked the interaction of CD28 and B7 was investigated in vivo, using the adoptive transfer of T cells derived from CTLA4-Fc-treated rats, and in vitro, using the proliferative response and cytokine production of MAA-T cells in the presence of CTLA4-Fc. RESULTS: CTLA4-Fc markedly reduced the incidence and severity of EAAU in Lewis rats after sensitization with MAA. The adoptive transfer of sensitized T cells from CTLA4-Fc-treated donors did not induce EAAU in naive recipients. CTLA4-Fc inhibited the expansion of antigen-specific MAA-T cells and the production of TNF-alpha. CONCLUSIONS: The costimulatory signal delivered through CD28-B7 is required for the induction and pathogenesis of EAAU. In the absence of this signal, antigen-specific expansion of MAA reactive T cells as well as production of TNF-alpha is inhibited. Abrogation of this costimulatory signal may be an important therapeutic option for EAAU.

Abatacept↗

PubMed2001

[Sequencing of inhA in drug-resistant Mycobacterium tuberculosis isolates].

OBJECTIVE: To determine and characterize inhA mutations of drug-resistant isolates of Mycobacterium tuberculosis. METHODS: PCR products of inhA of drug-resistant and susceptible isolates and H(37)R(v) were purified, cloned and analyzed by ABI 377 auto-DNA sequencing system. RESULTS: 11 out of 17 drug-resistant M. Tuberculosis isolates were detected having inhA variations. 10 out of the 11 strains with variations had at least one missense mutation. The variations consisted of point mutation (transition, transversion and deletion). Molecular mechanisms were different from strain to strain. 8 of 13 (62%) strains had both katG and inhA mutations. 18 variation positions and mechanisms different from previous report have been described. CONCLUSION: These results suggested that binding sites decrease caused by inhA point mutations be associated with M. tuberculosis' resistance to INH and EMB.

Amino Acid Sequence↗

PubMed2001

[Study of chemical constituents of essential oil from flowers of Mikania micrantha H.B.K].

The essential oil from flowers of Mikania micrantha H.B.K were extracted and its chemical constituents were analyzed by GC/MS. Forty-two compounds were identified and the main compounds with high contents were beta-cubebene (12.95%), allo-aromadendrene (11.67%), beta-caryophyllene (9.17%), 1H-inden-1-one, 5-(1, 1-dimethylethyl)-2, 3-(6.23%), beta-himaohalene (4.56%), trans-alpha-bergamotene (4.09%), limonene (3.68%), beta-ocimene (2.53%).

Azulenes↗

PubMed2000

Rit, a non-lipid-modified Ras-related protein, transforms NIH3T3 cells without activating the ERK, JNK, p38 MAPK or PI3K/Akt pathways.

The biological functions of Rit (Ras-like protein in tissues) and Rin (Ras-like protein in neurons), members of a novel branch of Ras-related GTP-binding proteins that are approximately 50% identical to Ras, have not been characterized. Therefore, we assessed their activity in growth control, transformation and signaling. NIH cells stably expressing a constitutively activated mutant of Rit [Rit(79L)] (analogous to the oncogenic mutant H-Ras(61L)) demonstrated strong growth transformation, proliferating rapidly in low serum and forming colonies in soft agar and tumors in nude mice. Although Rit(79L) alone did not promote morphologically transformed foci, it cooperated with both Raf and Rho A to form Rac/Rho-like foci. Rin [Rin(78L)] cooperated only with Raf. Rit(79L) but not Rin(78L) stimulated transcription from luciferase reporter constructs regulated by SRF, NF-kappaB, Elk-1 and Jun. However, neither activated ERK, JNK or p38, or PI3-K/Akt kinases in immune complex kinase assays. Interestingly, although Rit lacks any known recognition signal for C-terminal lipidation, Rit-transformed cell growth and survival in low serum is dependent on a farnesylated protein, as treatment with farnesyltransferase inhibitors caused apoptosis. Rin cooperated with Raf in focus assays but did not otherwise function in these assays, perhaps due to a lack of appropriate effector pathways in NIH3T3 fibroblasts for this neural-specific Ras family member. In summary, although Rit shares most core effector domain residues with Ras, our results suggest that Rit uses novel effector pathways to regulate proliferation and transformation.

3T3 Cells↗

PubMed2000

A novel RalGEF-like protein, RGL3, as a candidate effector for rit and Ras.

The small GTPase Rit is a close relative of Ras, and constitutively active Rit can induce oncogenic transformation. Although the effector loops of Rit and Ras are highly related, Rit fails to interact with the majority of the known Ras candidate effector proteins, suggesting that novel cellular targets may be responsible for Rit transforming activity. To gain insight into the cellular function of Rit, we searched for Rit-binding proteins by yeast two-hybrid screening. We identified the C-terminal Rit/Ras interaction domain of a protein we have designated RGL3 (Ral GEF-like 3) that shares 35% sequence identity with the known Ral guanine nucleotide exchange factors (RalGEFs). RGL3, through a C-terminal 99-amino acid domain, interacted in a GTP- and effector loop-dependent manner with Rit and Ras. Importantly, RGL3 exhibited guanine nucleotide exchange activity toward the small GTPase Ral that was stimulated in vivo by the expression of either activated Rit or Ras. These data suggest that RGL3 functions as an exchange factor for Ral and may serve as a downstream effector for both Rit and Ras.

Amino Acid Sequence↗

PubMed2000

Rem2, a new member of the Rem/Rad/Gem/Kir family of Ras-related GTPases.

Here we report the molecular cloning and biochemical characterization of Rem2 (for Rem, Rad and Gem-related 2), a novel GTP-binding protein identified on the basis of its homology with the Rem, Rad, Gem and Kir (RGK) family of Ras-related small GTP-binding proteins. Rem2 mRNA was detected in rat brain and kidney, making it the first member of the RGK family to be expressed at relatively high levels in neuronal tissues. Recombinant Rem2 binds GTP saturably and exhibits a low intrinsic rate of GTP hydrolysis. Surprisingly, the guanine nucleotide dissociation constants for both Rem2 and Rem are significantly different than the majority of the Ras-related GTPases, displaying higher dissociation rates for GTP than GDP. Localization studies with green fluorescent protein (GFP)-tagged recombinant protein fusions indicate that Rem2 has a punctate, plasma membrane localization. Deletion of the C-terminal seven amino acid residues that are conserved in all RGK family members did not affect the cellular distribution of the GFP fusion protein, whereas a larger deletion, including much of the polybasic region of the Rem2 C-terminus, resulted in its redistribution to the cytosol. Thus Rem2 is a GTPase of the RGK family with distinctive biochemical properties and possessing a novel cellular localization signal, consistent with its having a unique role in cell physiology.

Amino Acid Sequence↗

PubMed2000

Nicotine dependence and its familial aggregation in Chinese.

BACKGROUND: Nicotine dependence is a significant public health problem. This study attempted to characterize the prevalence and familial aggregation of nicotine dependence in China. METHODS: In 1998, we initiated a community-based cross-sectional study among residents of the Yuexi County in Anqing, China. A total of 991 current smokers from 488 randomly selected nuclear families were recruited and surveyed by use of the standardized Fagerstrom Test of Nicotine Dependence (FTND) questionnaire and the Revised Tolerance Questionnaire (RTQ). All study subjects were offspring in their respective nuclear families, and 478 male-male pairs (aged 41.7 +/- 12.1 years) were finally used for data analyses, because the number of female current smokers (n = 5) was too small. RESULTS: The correlation coefficient of the FTND and the RTQ scores was as high as 0.84 (P < 0.0001). Nicotine dependence, defined as an FTND score > or =8 or an RTQ score > or =28, had a prevalence of 12.7% and 11.1%, respectively. The respective sibling recurrent risk was 1.7 and 2.4, according to the FTND or the RTQ criteria. The adjusted odds ratios and 95% CI of nicotine dependence of second siblings in families in which the first sibling was nicotine dependent were 2.13 (95% CI: 1.02-4.43) and 3.50 (95% CI: 1.65-7.36) respectively, according to the FTND and RTQ criteria. CONCLUSIONS: The prevalence of nicotine dependence in male current smokers in China was comparable to that reported in previous US and European studies. Our findings suggest that genetic influences may play an important role in vulnerability to nicotine addiction.

Adult↗

PubMed2000

[Clinical observation of palitaxel in the treatment of gynecologic malignant tumors].

OBJECTIVE: To observe the therapeutic effect of palitaxel. METHODS: Of 37 cases, 33 were treated when tumor recurrence occurred after surgery or chemotherapy. There were 27 cases with ovarian cancer, 6 with fallopian tube cancer. 3 with cervix cancer, and 1 with endometrium cancer. In all cases, diagnosis was confirmed by histopathology. Palitaxel (135-150 mg/m2) was administered i.v. or i.p. once every three werks in combination with cisplatin (PDD) 60 mg/m2 and cyclophosphamide (CTX) 60 mg/d. Antihistaminics and antiemetic were given prior to palitaxel. The results of treatment were compared with those in 37 cases treated in the some time period with PAC or VBP regimen. RESULTS: The overall median survival time of the control group was 4 months, and 8.5 months in the palitaxel treated group (P < 0.001). The response rate was 18.9% and 48.6% respectively (P < 0.005). The major toxic effects was myelosuppression and alopecia. CONCLUSION: Palitaxel is effective in the treatment of advanced gynecological tumors.

Adult↗

PubMed2000

[A comparison between latanoprost and timolol in treatment of patients with primary open-angle glaucoma and ocular hypertension].

OBJECTIVE: To evaluate the therapeutic value of latanoprost on glaucoma. METHODS: In an open-label fashion, multicenter, randomized control clinical trial, the efficacy and adverse drug reactions of topical application of 0.005% latanoprost once daily were compared with that of 0.5% timolol twice daily for 12 weeks in patients with open-angle glaucoma or ocular hypertension. RESULTS: The study included 128 patients (63 patients in latanoprost group and 65 patients in timolol group) and 117 patients remained at the end of the study (60 cases in latanoprost group and 57 cases in timolol group). Comparing 12 weeks with baseline diurnal intraocular pressure (IOP), the IOP reduction (mean +/- standard deviation) in latanoprost group was (7.5 +/- 0.3) mm Hg (1 mm Hg = 0.133 kPa) (32%, t = 22.73, P < 0.0001) greater than the reduction in timolol group (6.1 +/- 0.3) mm Hg (26%, t = 17.94, P < 0.0001), the difference between the two groups being significant (F = 9.54, P = 0.0026). Two patients treated with timolol and none treated with latanoprost were withdrawn from the study because of inadequate IOP control; 3 patients with latanoprost had foreign body sensation. In latanoprost group, there was one patient whose eyelashes became darker and longer at the last visit (the 12th week). No ocular and systemic adverse events related to the two drugs were found. CONCLUSION: It is demonstrated that 0.005% latanoprost topically applied once daily is well tolerated and more effective in reducing IOP than 0.5% timolol topically applied twice daily. Thus, latanoprost has the potential to be a new first-line antiglaucoma drug.

Adrenergic beta-Antagonists↗

PubMed1999

Biochemical characterization of the Ras-related GTPases Rit and Rin.

We report the biochemical characterization of Rit and Rin, two members of the Ras superfamily identified by expression cloning. Recombinant Rit and Rin bind GTP and exhibit intrinsic GTPase activity. Conversion of Gln to Leu at position 79 (for Rit) or 78 (for Rin) (equivalent to position 61 in Ras) resulted in a complete loss of GTPase activity. Surprisingly, significant differences were found when the guanine nucleotide dissociation constants of Rit and Rin were compared with the majority of Ras-related GTPases. Both proteins display higher k(off) values for GTP than GDP in the presence of 10 mM Mg(2+). These GTP dissociation rates are 5- to 10-fold faster than most Ras-like GTPases. Despite these unique biochemical properties, our data support the notion that both Rit and Rin function as nucleotide-dependent molecular switches. To begin to address whether these proteins act as regulators of distinct signaling pathways, we examined their interaction with a series of known Ras-binding proteins by yeast two-hybrid analysis. Although Rit, Rin, and Ras have highly related effector domain sequences, Rit and Rin were found to interact with the known Ras binding proteins RalGDS, Rlf, and AF-6/Canoe but not with the Raf kinases, RIN1, or the p110 subunit of phosphatidylinositol 3-kinase. These interactions were GTP and effector domain dependent and suggest that RalGDS, Rlf, and AF-6 are Rit and Rin effectors. Their biochemical properties and interaction with a subset of known Ras effector proteins suggest that Rit and Rin may play important roles in the regulation of signaling pathways and cellular processes distinct from those controlled by Ras.

Cloning, Molecular↗

PubMed1999

Slow accumulation of active mitogen-activated protein kinase during thymocyte differentiation regulates the temporal pattern of transcription factor gene expression.

Thymocyte-positive selection is believed to result from low affinity/avidity interactions of TCR and MHC proteins, but how these weak interactions translate into downstream biochemical signals and how such signals modulate gene expression is unknown. Using a culture system where isolated immature thymocytes can be induced to differentiate along the CD4 lineage pathway, we show that sustained low level mitogen-activated protein/extracellular regulated kinase activity is required for cell differentiation and survival. Furthermore, induction of mitogen-activated protein/extracellular regulated kinase activity is surprisingly slow under conditions that induce differentiation. This pattern of kinase activity not only selects which genes are expressed but also regulates the temporal pattern of expression of transcription factor genes that are induced during double-positive thymocyte differentiation.

Animals↗