Identification of the N-linked glycosylation sites of the human relaxin receptor and effect of glycosylation on receptor function

The relaxin receptor, RXFP1, is a member of the leucine-rich repeat-containing G-protein-coupled receptor (LGR) family. These receptors are characterized by a large extracellular ectodomain containing leucine-rich repeats which contain the primary ligand binding site. RXFP1 contains six putative Asn-linked glycosylation sites in the ectodomain at positions Asn-14, Asn-105, Asn-242, Asn-250, Asn-303, and Asn-346, which are highly conserved across species. N-Linked glycosylation is the most common post-translational modification of G-protein-coupled receptors, although its role in modulating receptor function differs. We herein investigate the actual N-linked glycosylation status of RXFP1 and the functional ramifications of these post-translational modifications. Site-directed mutagenesis was utilized to generate single- or multiple-glycosylation site mutants of FLAG-tagged human RXFP1 which were then transiently expressed in HEK-293T cells. Glycosylation status was analyzed by immunoprecipitation and Western blot and receptor function analyzed with an anti-FLAG ELISA, (33)P-H2 relaxin competition binding, and cAMP activity measurement. All of the potential N-glycosylation sites of RXFP1 were utilized in HEK-293T cells, and importantly, disruption of glycosylation at individual or combinations of double and triple sites had little effect on relaxin binding. However, combinations of glycosylation sites were required for cell surface expression and cAMP signaling. In particular, N-glycosylation at Asn-303 of RXFP1 was required for optimal intracellular cAMP signaling. Hence, as is the case for other LGR family members, N-glycosylation is essential for the transport of the receptor to the cell surface. Additionally, it is likely that glycosylation is also essential for the conformational changes required for G-protein coupling and subsequent cAMP signaling.

Understanding the differences between the wear of metal-on-metal and ceramic-on-metal total hip replacements

Hip simulator studies have been carried out extensively to understand and test artificial hip implants in vitro as an efficient alternative to obtaining long-term results in vivo. Recent studies have shown that a ceramic-on-metal material combination lowers the wear by up to 100 times in comparison with a typical metal-on-metal design. The reason for this reduction remains unclear and for this reason this study has undertaken simple tribometer tests to understand the fundamental material loss mechanisms in two material combinations: metal-on-metal and ceramic-on-ceramic.

A simple-configuration reciprocating pin-on-plate wear study was performed under open-circuit potential (OCP) and with applied cathodic protection (CP) in a serum solution using two tribological couples: firstly, cobalt—chromium (Co—Cr) pins against Co—Cr plates; secondly, Co—Cr pins against alumina (Al2O3) plates. The pin and plate surfaces prior to and after testing were examined by profilometry and scanning electron microscopy.

The results showed a marked reduction in wear when CP was applied, indicating that total material degradation under the OCP condition was attributed to corrosion processes. The substitution of the Co—Cr pin with an Al2O3 plate also resulted in a dramatic reduction in wear, probably due to the reduction in the corrosion—wear interactions between the tribological pair.

Effect of inhaled formaldehyde on learning and memory of mice

In this study, we investigated the effect of inhaled formaldehyde on learning and memory capacity. After exposure to 0 (control), 1 and 3 mg/m(3) of gaseous formaldehyde respectively, the behavior of mice in a Morris water maze, the expression of NR1, NR2B mRNA and oxidative damage levels in mice brain were analyzed. The water maze performance, the activities of dismutase superoxide (SOD) and levels of glutathione (GSH) decreased significantly in 3 mg/m(3) group (P < 0.01, compared with control group); while malondialdehyde (MDA) contents and expression of NR1 and NR2B genes increased significantly after exposure to 3 mg/m(3) of gaseous formaldehyde (P < 0.05, <0.01, <0.01, compared with control group). These findings indicate that inhaled formaldehyde negatively affects learning and memory at 3 mg/m(3) of gaseous formaldehyde but not at lower levels. Oxidative stress-induced neuron damages in the brain may be the possible mechanism for these effects.

PRACTICAL IMPLICATIONS

This study indicates that inhaled formaldehyde starts to negatively affect learning and memory at a middle concentration of formaldehyde without interference of other indoor air pollutants. Oxidative damage, and the alteration of NMDA receptor expression, which were induced by formaldehyde inhalation, may be the possible mechanism for gaseous formaldehyde-induced neurotoxicity.

Immunological properties of a fusion protein containing nucleocapsid protein and glycoprotein Gn of Hantaan virus

Escherichia coli and the baculovirus Bac-to-Bac system were used to express chimeric gene GnS0.7 consisting of glycoprotein Gn gene and the 0.7 kb fragment of S genome segment carrying nucleoprotein (N) gene of Hantaan virus (HTNV). The expressed fusion protein GnN0.7 was recognized by monoclonal antibodies (MAbs) to HTNV Gn glycoprotein and N protein, respectively. Its molecular mass as determined by Western blot analysis corresponded to the predicted value. The mice immunized with insect Spodoptera frugiperda (Sf9) cells transfected with recombinant baculovirus carrying GnS0.7 gene, produced serum antibodies with titer up to 3,200 as assayed by immunofluorescence. Moreover, immunized mice showed positive proliferation index for splenocytes stimulated with HTNV Gn and N, respectively. These results indicated that insect Sf9 cells infected with the recombinant baculovirus expressed a fully biologically active fusion protein that elicited not only humoral but also cellular immune response in mice. Hence, this protein may be used as a genetically engineered subunit HTNV vaccine representing efficacious and safe alternative to traditional vaccines.

Regulation of class IA PI3Ks

Class IA PI3Ks (phosphoinositide 3-kinases) regulate a wide range of cellular responses through the production of PI(3,4,5)P(3) (phosphatidylinositol 3,4,5-trisphosphate) in cellular membranes. They are activated by receptor tyrosine kinases, by Ras and Rho family GTPases, and in some cases by G(betagamma) subunits from trimeric G-proteins. Crystallographic studies on the related class IB PI3Kgamma, and biochemical and structural studies on the class IA PI3Ks, have led to new insights into how these critical enzymes are regulated in normal cells and how mutations can lead to their constitutive activation in transformed cells. The present paper will discuss recent studies on the regulation of class I (p85/p110) PI3Ks, with a focus on the role of SH2 domains (Src homology 2 domains) in the p85 regulatory subunit in modulating PI3K activity.

A novel unconventional antigen MPD5 elicits anti-tumor humoral immune responses in a subset of patients with polycythemia vera

In an effort to define the antigenic mechanism that contributes to beneficial therapeutic outcome in patients with polycythemia vera (PV), we screened a human testis cDNA library with serological cloning derived from sera of three PV patients who had undergone therapeutic-induced remission. As a result, we identified a novel antigen, MPD5, which belongs to the group of cryptic antigens with unconventional genomic intron/exon structure. Moreover, MPD5 elicited IgG antibody responses in a subset of PV patients who had benefited from a variety of therapies--including IFN-alpha, Hydroxyurea, Imatinib mesylate, Anagrelide, and phlebotomy--but not in untreated PV patients or healthy donors, suggesting that MPD5 is a PV-associated, therapy-related antigen. In the granulocytes of PV patients who are responsive to therapy, upregulated MPD5 expression may serve to enhance immune responses. These findings provide new insight into the mechanism underlying regulation of the self-antigen repertoire that elicits anti-tumor immune responses in patients with myeloproliferative diseases, indicating the potential of these self-antigens as targets of novel immunotherapy.

Polymorphisms and drug resistance analysis of HIV-1 CRF01_AE strains circulating in Fujian Province, China

BACKGROUND

The database of genotypic drug resistance mutations in HIV-1 subtype B circulating in developed industrial countries has been well established; however, little is known regarding the prevalence of genotypic resistance patterns in patients harboring non-subtype-B HIV-1 variants in most Asian countries.

OBJECTIVE

To characterize the polymorphisms and emergence of drug-resistance mutations, resistance to antiretroviral drugs in naïve and pretreated patients infected with HIV-1 CRF01_AE isolates in Fujian province, China.

METHODS

HIV-1 pol amplicons from 52 pre- and 14 post-treatment samples were obtained by reverse transcription-polymerase chain reaction (RT-PCR) and sequencing. All of the 14 antiretroviral-treated patients were under a fixed regimen of stavudine (d4T), lamivudine (3TC) and nevirapine (NVP), and they had been on treatment for a mean of 6 months (SD, 4 months). The sequence data were analyzed using the Bioedit software, and the data regarding drug resistance mutations were obtained using the Stanford software ( http://hivdb.stanford.edu ).

RESULTS

In comparison with the consensus sequence of B strains, the most common protease polymorphisms in HIV-1 CRF01_AE strains prevailing in Fujian Province, China, were I13V (76.9%), E35D (76.9%), M36I (100%), R41K (98.1%), H69K (90.4%), and L89M (96.2%). Protease mutations between CRF01_AE strains and B' variants prevailing in China were observed. The proportion of substitutions L63P, A71T/V, V77I and I93L in subtype B' sequences was considerably higher than in CRF01_AE viruses, while the proportion of L10I, M36I and K20R/I substitutions in subtype B' sequences was relatively lower than in CRF01_AE strains. A high level of resistance to nucleoside reverse transcriptase inhibitors (NRTIs) (28.6%, 4/14) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) (35.7%, 5/14) was found in treatment-experienced patients. High-level resistance to nevirapine (NVP) and lamivudine (3TC) was found in the stavudine/lamivudine/nevirapine (d4T/3TC/NVP) treatment regimen. The overall drug resistance rate was 42.9% (6/14), the resistance rates to two and to all three drugs under treatment were 14.3% (2/14) and 7.1% (1/14), respectively.

CONCLUSION

This study is the first report on polymorphisms and emergence of drug-resistance mutations in HIV-1 subtype CRF01_AE prevailing in China. These findings provide useful information on global HIV genetic variability and non-B drug resistance.

Association between hepatitis B virus infection and HLA-DRB1 genotyping in Shaanxi Han patients in northwestern China

Hepatitis B virus (HBV) infection is a major public health problem worldwide. The mechanism of susceptibility to chronic persistent HBV infection is not well clarified, while the outcome of HBV infection mainly depends on the host immune response. Human leukocyte antigen (HLA) class II molecule is an integral component of the immune response on which majority of host genetic studies have concentrated. Many different HLA class II alleles have been demonstrated to play roles in HBV infection. In this study, the association between HBV infection and HLA-DRB1 alleles in Han individuals in northwestern China was studied for the first time. Two hundred and fifty Shaanxi Han individuals were categorized into three different groups: the HBV-infected patient group (n = 108), the spontaneously cleared control group (n = 108) and the unexposed group (n = 34). DRB1*04, DRB1*09, DRB1*12 and DRB1*15 were the most common genotypes in all the groups. The allele frequencies of HLA-DRB1*03 [10.6% of HBV-infected patients vs 3.7% of spontaneously cleared controls, odds ratios (OR) = 3.10, Pc = 0.008, P < 0.05] and HLA-DRB1*07 (17.6% of HBV-infected patients vs 9.3% of spontaneously cleared controls, Pc = 0.016, OR = 2.09, P < 0.05) were markedly higher in the HBV-infected group. But the allele frequencies of HLA-DRB1*15 (6.9% of HBV-infected patients vs 13.4% of spontaneously cleared controls Pc = 0.039, OR = 0.48, P < 0.05) were obviously lower than that of the spontaneously cleared controls. The above data indicate that HLA-DRB1*03 and HLA-DRB1*07 are related to susceptibility to chronic HBV infection, and DRB1*15 is negatively related to persistence to chronic HBV infection among people in northwestern China. Similar results were got for DRB1*03 and 15 alleles between the HBV-infected patients (n = 108) and 46 HBV seronegative spouses of the HBV patients, who were high-risk group for HBV infection. The above results suggest that host HLA class II gene is an important factor in determination of the outcome of HBV infection.

HLA-A2.1-restricted T cells react to SEREX-defined tumor antigen CML66L and are suppressed by CD4+CD25+ regulatory T cells

The question of whether T cell responses to SEREX-defined tumor antigens are under regulation of naturally occurring CD4+CD25+ regulatory T cells (nTreg cells) has not been answered. To address this issue, we first identified an HLA-A2.1-restricted T cell antigen epitope of SEREX-identified tumor antigen CML66L, 66Pa. The HLA-A2.1/66Pa peptide complex in vitro stimulated the in vivo-primed T cells as shown by increased T cell proliferation, higher secretion of the T cell cytokine interferon-gamma (IFN-gamma), increased production of intracellular IFN-gamma in CD8+ T cells, and higher T cell-mediated cytotoxicities of CML66L+ human tumor cells. This suggests that CML66L elicits T cell immune responses. We also developed a novel internal reference epitope for identification of T cell epitopes by construction of chimeric CML66L containing myeloid antigen proteinase 3 epitope Pr1 as a control. Finally, we found that nTreg cells regulates T cell responses to 66Pa, and that depletion of nTreg cells via a pro-apoptotic protein Bax-dependent mechanism enhances polyclonal T cell responses to 66Pa. These findings provide new insights into the T cell participation in SEREX-defined anti-tumor immune responses and novel direction in enhancement of anti-leukemia immunotherapy by modulation of homeostasis of nTreg cells.

Regulation of class III (Vps34) PI3Ks

The class III PI3K (phosphoinositide 3-kinase), Vps34 (vacuolar protein sorting 34), was first identified as a regulator of vacuolar hydrolase sorting in yeast. Unlike other PI3Ks, the Vps34 lipid kinase specifically utilizes phosphatidylinositol as a substrate, producing the single lipid product PtdIns3P. While Vps34 has been studied for some time in the context of endocytosis and vesicular trafficking, it has more recently been implicated as an important regulator of autophagy, trimeric G-protein signalling, and the mTOR (mammalian target of rapamycin) nutrient-sensing pathway. The present paper will focus on studies that describe the regulation of hVps34 (human Vps34) intracellular targeting and enzymatic activity in yeast and mammalian cells.

Processing sites are different in the generation of HLA-A2.1-restricted, T cell reactive tumor antigen epitopes and viral epitopes

In order to improve the processing efficiency of T cell tumor antigen epitopes, this bioinformatic study compares proteolytic sites in the generation of 47 experimentally identified HLA-A2.1-restricted immunodominant tumor antigen epitopes to those of 52 documented HLA-A2.1-restricted immunodominant viral antigen epitopes. Our results show that the amino acid frequencies in the C-terminal cleavage sites of the tumor antigen epitopes, as well as several positions within the 10 amino acid (aa) flanking regions, are significantly different from those of the viral antigen epitopes. In the 9 amino acid epitope region, frequencies differed somewhat in the secondary-anchored amino acid residues on E3 (the third aa of the epitope), E4, E6, E7 and E8; however, frequencies in the primary-anchored positions, on E2 and E9, for binding in the HLA-A2.1 groove, remained almost identical. The most frequently occurring amino acid pairs in both N-terminal and C-terminal cleavage sites in the generation of tumor antigen epitopes were different from those of the viral antigen epitopes. Our findings demonstrate for the first time that these two groups of epitopes may be cleaved by distinct sets of proteasomes and peptidases or similar enzymes with lower efficiencies for tumor epitopes. In the future, in order to more effectively generate tumor antigen epitopes, targeted activation of the immunoproteasomes and peptidases that mediate the cleavage of viral epitopes could be achieved, thus enhancing our potential for antigen-specific tumor immunotherapy.

Reinforcing effects of morphine are reduced in tissue plasminogen activator-knockout mice

Tissue plasminogen activator (tPA) plays a key role in neuroplasticity. We have recently demonstrated that the tPA-plasmin system is involved in the rewarding effects of drugs of abuse by regulating the release of dopamine in the nucleus accumbens. In the present study, we investigated whether tPA is involved in the reinforcing properties of morphine in a paradigm of drug self-administration. Eight-week-old tPA knockout and wild-type control mice were subjected to a single 24-h session of morphine self-administration under a fixed ratio (FR) 2 or a progressive ratio (PR) schedule of reinforcement after eight daily 30-min sessions of nose-poke training. tPA knockout mice responded significantly more often for morphine self-administration in a dose-dependent manner as compared with wild-type control mice. Under the PR schedule of morphine reinforcement, however, tPA knockout mice showed a lower breaking point than wild-type control mice. There was no significant difference in food-reinforced operant behavior, breaking points to food pellets, and saline self-administration between the two genotypes. The increased responding in tPA knockout mice under the FR2 schedule was significantly attenuated by the dopamine D1 receptor antagonist SCH23390 (0.3 mg/kg), whereas SCH23390, at a dose range of 0.03-2.0 mg/kg, demonstrated biphasic effects on morphine self-administration in wild-type control mice. Our findings suggest that the reinforcing effects of morphine are reduced in tPA knockout mice. Modulation of the tPA system in the brain may be a potential target against drugs of abuse.