Theileria parva-transformed T cells show enhanced resistance to Fas/Fas ligand-induced apoptosis.

Lymphocyte homeostasis is regulated by mechanisms that control lymphocyte proliferation and apoptosis. Activation-induced cell death is mediated by the expression of death ligands and receptors, which, when triggered, activate an apoptotic cascade. Bovine T cells transformed by the intracellular parasite Theileria parva proliferate in an uncontrolled manner and undergo clonal expansion. They constitutively express the death receptor Fas and its ligand, FasL but do not undergo apoptosis. Upon elimination of the parasite from the host cell by treatment with a theilericidal drug, cells become increasingly sensitive to Fas/FasL-induced apoptosis. In normal T cells, the sensitivity to death receptor killing is regulated by specific inhibitor proteins. We found that anti-apoptotic proteins such as cellular (c)-FLIP, which functions as a catalytically inactive form of caspase-8, and X-chromosome-linked inhibitor of apoptosis protein (IAP) as well as c-IAP, which can block downstream executioner caspases, are constitutively expressed in T. parva-transformed T cells. Expression of these proteins is rapidly down-regulated upon parasite elimination. Antiapoptotic proteins of the Bcl-2 family such as Bcl-2 and Bcl-x(L) are also expressed but, in contrast to c-FLIP, c-IAP, and X-chromosome-linked IAP, do not appear to be tightly regulated by the presence of the parasite. Finally, we show that, in contrast to the situation in tumor cells, the phosphoinositide 3-kinase/Akt pathway is not essential for c-FLIP expression. Our findings indicate that by inducing the expression of antiapoptotic proteins, T. parva allows the host cell to escape destruction by homeostatic mechanisms that would normally be activated to limit the continuous expansion of a T cell population.

Inhibition of Mitogen-Activated Protein Kinase Erk1/2 Promotes Protein Degradation of ATP Binding Cassette Transporters A1 and G1 in CHO and in HuH7 cells.

Signal transduction modulates expression and activity of cholesterol transporters. We recently demonstrated that the Ras/mitogen-activated protein kinase (MAPK) signaling cascade regulates protein stability of Scavenger Receptor BI (SR-BI) through Proliferator Activator Receptor (PPARα) -dependent degradation pathways. In addition, MAPK (Mek/Erk 1/2) inhibition has been shown to influence liver X receptor (LXR) -inducible ATP Binding Cassette (ABC) transporter ABCA1 expression in macrophages. Here we investigated if Ras/MAPK signaling could alter expression and activity of ABCA1 and ABCG1 in steroidogenic and hepatic cell lines. We demonstrate that in Chinese Hamster Ovary (CHO) cells and human hepatic HuH7 cells, extracellular signal-regulated kinase 1/2 (Erk1/2) inhibition reduces PPARα-inducible ABCA1 protein levels, while ectopic expression of constitutively active H-Ras, K-Ras and MAPK/Erk kinase 1 (Mek1) increases ABCA1 protein expression, respectively. Furthermore, Mek1/2 inhibitors reduce ABCG1 protein levels in ABCG1 overexpressing CHO cells (CHO-ABCG1) and human embryonic kidney 293 (HEK293) cells treated with LXR agonist. This correlates with Mek1/2 inhibition reducing ABCG1 cell surface expression and decreasing cholesterol efflux onto High Density Lipoproteins (HDL). Real Time reverse transcriptase polymerase chain reaction (RT-PCR) and protein turnover studies reveal that Mek1/2 inhibitors do not target transcriptional regulation of ABCA1 and ABCG1, but promote ABCA1 and ABCG1 protein degradation in HuH7 and CHO cells, respectively. In line with published data from mouse macrophages, blocking Mek1/2 activity upregulates ABCA1 and ABCG1 protein levels in human THP1 macrophages, indicating opposite roles for the Ras/MAPK pathway in the regulation of ABC transporter activity in macrophages compared to steroidogenic and hepatic cell types. In summary, this study suggests that Ras/MAPK signaling modulates PPARα- and LXR-dependent protein degradation pathways in a cell-specific manner to regulate the expression levels of ABCA1 and ABCG1 transporters.

Impaired natural killing of MHC class I-deficient targets by NK cells expressing a catalytically inactive form of SHP-1.

NK cell function is negatively regulated by MHC class I-specific inhibitory receptors. Transduction of the inhibitory signal involves protein tyrosine phosphatases such as SHP-1 (SH2-containing protein tyrosine phosphatase-1). To investigate the role of SHP-1 for NK cell development and function, we generated mice expressing a catalytically inactive, dominant-negative mutant of SHP-1 (dnSHP-1). In this paper we show that expression of dnSHP-1 does not affect the generation of NK cells even though MHC receptor-mediated inhibition is partially impaired. Despite this defect, these NK cells do not kill syngeneic, normal target cells. In fact dnSHP-1-expressing NK cells are hyporesponsive toward MHC-deficient target cells, suggesting that non-MHC-specific NK cell activation is significantly reduced. In contrast, these NK cells mediate Ab-dependent cell-mediated cytotoxicity and prevent the engraftment with beta2-microglobulin-deficient bone marrow cells. A similar NK cell phenotype is observed in viable motheaten (mev) mice, which show reduced SHP-1 activity due to a mutation in the Shp-1 gene. In addition, NK cells in both mouse strains show a tendency to express more inhibitory MHC-specific Ly49 receptors. Our results demonstrate the importance of SHP-1 for the generation of functional NK cells, which are able to react efficiently to the absence of MHC class I molecules from normal target cells. Therefore, SHP-1 may play an as-yet-unrecognized role in some NK cell activation pathways. Alternatively, a reduced capacity to transduce SHP-1-dependent inhibitory signals during NK cell development may be compensated by the down-modulation of NK cell triggering pathways.

Processing of the circumsporozoite protein in infected hepatocytes is not dependent on aspartic proteases

CD8(+) T cells play a major role in the protective immune response against the liver stage of malaria. It was previously shown that the circumsporozoite protein (CSP) is processed and presented to specific T cells by both traversed and infected hepatocytes, but their respective antigen processing requirements were not completely defined. In the present study, we show that in vitro processing of the Plasmodium berghei CSP by infected mouse primary hepatocytes is exclusively dependent on proteasomes, while aspartic proteases are also needed in the case of traversed hepatocytes

Loss-of-function mutations of an inhibitory upstream ORF in the human hairless transcript cause Marie Unna hereditary hypotrichosis.

Marie Unna hereditary hypotrichosis (MUHH) is an autosomal dominant form of genetic hair loss. In a large Chinese family carrying MUHH, we identified a pathogenic initiation codon mutation in U2HR, an inhibitory upstream ORF in the 5' UTR of the gene encoding the human hairless homolog (HR). U2HR is predicted to encode a 34-amino acid peptide that is highly conserved among mammals. In 18 more families from different ancestral groups, we identified a range of defects in U2HR, including loss of initiation, delayed termination codon and nonsense and missense mutations. Functional analysis showed that these classes of mutations all resulted in increased translation of the main HR physiological ORF. Our results establish the link between MUHH and U2HR, show that fine-tuning of HR protein levels is important in control of hair growth, and identify a potential mechanism for preventing hair loss or promoting hair removal.

Ubiquitin-specific protease 2-45 (Usp2-45) binds to epithelial Na+ channel (ENaC)-ubiquitylating enzyme Nedd4-2.

Regulation of the epithelial Na(+) channel (ENaC) by ubiquitylation is controlled by the activity of two counteracting enzymes, the E3 ubiquitin-protein ligase Nedd4-2 (mouse ortholog of human Nedd4L) and the ubiquitin-specific protease Usp2-45. Previously, Usp2-45 was shown to decrease ubiquitylation and to increase surface function of ENaC in Xenopus laevis oocytes, whereas the splice variant Usp2-69, which has a different N-terminal domain, was inactive toward ENaC. It is shown here that the catalytic core of Usp2 lacking the N-terminal domain has a reduced ability relative to Usp2-45 to enhance ENaC activity in Xenopus oocytes. In contrast, its catalytic activity toward the artificial substrate ubiquitin-AMC is fully maintained. The interaction of Usp2-45 with ENaC exogenously expressed in HEK293 cells was tested by coimmunoprecipitation. The data indicate that different combinations of ENaC subunits, as well as the α-ENaC cytoplasmic N-terminal but not C-terminal domain, coprecipitate with Usp2-45. This interaction is decreased but not abolished when the cytoplasmic ubiquitylation sites of ENaC are mutated. Importantly, coimmunoprecipitation in HEK293 cells and GST pull-down of purified recombinant proteins show that both the catalytic domain and the N-terminal tail of Usp2-45 physically interact with the HECT domain of Nedd4-2. Taken together, the data support the conclusion that Usp2-45 action on ENaC is promoted by various interactions, including through binding to Nedd4-2 that is suggested to position Usp2-45 favorably for ENaC deubiquitylation.

Circulating matrix γ-carboxyglutamate protein (MGP) species are refractory to vitamin K treatment in a new case of Keutel syndrome.

Summary.  Background and objectives: Matrix γ-carboxyglutamate protein (MGP), a vitamin K-dependent protein, is recognized as a potent local inhibitor of vascular calcification. Studying patients with Keutel syndrome (KS), a rare autosomal recessive disorder resulting from MGP mutations, provides an opportunity to investigate the functions of MGP. The purpose of this study was (i) to investigate the phenotype and the underlying MGP mutation of a newly identified KS patient, and (ii) to investigate MGP species and the effect of vitamin K supplements in KS patients. Methods: The phenotype of a newly identified KS patient was characterized with specific attention to signs of vascular calcification. Genetic analysis of the MGP gene was performed. Circulating MGP species were quantified and the effect of vitamin K supplements on MGP carboxylation was studied. Finally, we performed immunohistochemical staining of tissues of the first KS patient originally described focusing on MGP species. Results: We describe a novel homozygous MGP mutation (c.61+1G>A) in a newly identified KS patient. No signs of arterial calcification were found, in contrast to findings in MGP knockout mice. This patient is the first in whom circulating MGP species have been characterized, showing a high level of phosphorylated MGP and a low level of carboxylated MGP. Contrary to expectations, vitamin K supplements did not improve the circulating carboxylated MGP levels. Phosphorylated MGP was also found to be present in the first KS patient originally described. Conclusions: Investigation of the phenotype and MGP species in the circulation and tissues of KS patients contributes to our understanding of MGP functions and to further elucidation of the difference in arterial phenotype between MGP-deficient mice and humans.

Vaccination with a recombinant protein encoding the tumor-specific antigen NY-ESO-1 elicits an A2/157-165-specific CTL repertoire structurally distinct and of reduced tumor reactivity than that elicited by spontaneous immune responses to NY-ESO-1-expressing Tumors.

In a recent vaccination trial assessing the immunogenicity of an NY-ESO-1 (ESO) recombinant protein administered with Montanide and CpG, we have obtained evidence that this vaccine induces specific cytolytic T lymphocytes (CTL) in half of the patients. Most vaccine-induced CTLs were directed against epitopes located in the central part of the protein, between amino acids 81 and 110. This immunodominant region, however, is distinct from another ESO CTL region, 157-165, that is a frequent target of spontaneous CTL responses in A2+ patients bearing ESO tumors. In this study, we have investigated the CTL responses to ESO 157-165 in A2+ patients vaccinated with the recombinant protein. Our data indicate that after vaccination with the protein, CTL responses to ESO 157-165 are induced in some, but not all, A2+ patients. ESO 157-165-specific CTLs induced by vaccination with the ESO protein were functionally heterogeneous in terms of tumor recognition and often displayed decreased tumor reactivity as compared with ESO 157-165-specific CTLs isolated from patients with spontaneous immune responses to ESO. Remarkably, protein-induced CTLs used T-cell receptors similar to those previously isolated from patients vaccinated with synthetic ESO peptides (Vbeta4.1) and distinct from those used by highly tumor-reactive CTLs isolated from patients with spontaneous immune responses (Vbeta1.1, Vbeta8.1, and Vbeta13.1). Together, these results demonstrate that vaccination with the ESO protein elicits a repertoire of ESO 157-165-specific CTLs bearing T-cell receptors that are structurally distinct from those of CTLs found in spontaneous immune responses to the antigen and that are heterogeneous in terms of tumor reactivity, being often poorly tumor reactive.

The ubiquitin-like protein LC3 regulates the Rho-GEF activity of AKAP-Lbc.

AKAP-Lbc is a member of the A-kinase anchoring protein (AKAP) family that has been recently associated with the development of pathologies, such as cardiac hypertrophy and cancer. We have previously demonstrated that, at the molecular level, AKAP-Lbc functions as a guanine nucleotide exchange factor (GEF) that promotes the specific activation of RhoA. In the present study, we identified the ubiquitin-like protein LC3 as a novel regulatory protein interacting with AKAP-Lbc. Mutagenesis studies revealed that LC3, through its NH(2)-terminal alpha-helical domain, interacts with two binding sites located within the NH(2)-terminal regulatory region of AKAP-Lbc. Interestingly, LC3 overexpression strongly reduced the ability of AKAP-Lbc to interact with RhoA, profoundly impairing the Rho-GEF activity of the anchoring protein and, as a consequence, its ability to promote cytoskeletal rearrangements associated with the formation of actin stress fibers. Moreover, AKAP-Lbc mutants that fail to interact with LC3 show a higher basal Rho-GEF activity as compared with the wild type protein and become refractory to the inhibitory effect of LC3. This suggests that LC3 binding maintains AKAP-Lbc in an inactive state that displays a reduced ability to promote downstream signaling. Collectively, these findings provide evidence for a previously uncharacterized role of LC3 in the regulation of Rho signaling and in the reorganization of the actin cytoskeleton.

Generation of a tightly regulated all-cis beta cell-specific tetracycline-inducible vector.

Ability to induce protein expression at will in a cell is a powerful strategy used by scientists to better understand the function of a protein of interest. Various inducible systems have been designed in eukaryotic cells to achieve this goal. Most of them rely on two distinct vectors, one encoding a protein that can regulate transcription by binding a compound X, and one hosting the cDNA encoding the protein of interest placed downstream of promoter sequences that can bind the protein regulated by compound X (e.g., tetracycline, ecdysone). The commercially available systems are not designed to allow cell- or tissue-specific regulated expression. Additionally, although these systems can be used to generate stable clones that can be induced to express a given protein, extensive screening is often required to eliminate the clones that display poor induction or high basal levels. In the present report, we aimed to design a pancreatic beta cell-specific tetracycline-inducible system. Since the classical two-vector based tetracycline-inducible system proved to be unsatisfactory in our hands, a single vector was eventually designed that allowed tight beta cell-specific tetracycline induction in unselected cell populations.

Localization of HLA-A2.1-restricted T cell epitopes in the circumsporozoite protein of Plasmodium falciparum.

Localization of human MHC class I-restricted T cell epitopes in the circumsporozoite (CS) protein of the human parasite Plasmodium falciparum is an important objective in the development of antimalarial vaccines. To this purpose, we synthesized a series of overlapping synthetic 20-mer peptides, spanning the entire sequence of the 7G8 CS molecule except for the central repeat B cell domain. The P.f.CS peptides were first tested for their ability to bind to the human MHC class I HLA-A2.1 molecule on T2, a human cell line. Subsequently, the use of a series of shorter peptide analogues allowed us to determine the optimal A2.1 binding sequence present in several of the 20-mers. Binding P.f.CS peptides were further tested for their capacity to activate PBL from HLA-A2.1+ immune donors living in a malaria-endemic area. Specific IFN-gamma production was detected in the supernatant of cultures of PBL from exposed individuals. Cytotoxic T cell lines and clones were derived from the PBL of one responder, and their activity was shown to be HLA-A2.1-restricted and specific for the peptide 334-342 of the CS protein. In addition, double transgenic HLA-A2.1 x human beta 2-microglobulin mice were immunized with peptide 1-10 of the CS protein. T cells derived from immune lymph nodes displayed a peptide-specific HLA-A2.1-restricted cytolytic activity after one in vitro stimulation.

Triiodothyronine has diverse and multiple stimulating effects on expression of the major myelin protein genes.

If the importance of triiodothyronine (T3) on brain development including myelinogenesis has long been recognized, its mechanism of action at the gene level is still not fully elucidated. We studied the effect of T3 on the expression of myelin protein genes in aggregating brain cell cultures. T3 increases the concentrations of mRNA transcribed from the following four myelin protein genes: myelin basic protein (Mbp), myelin-associated glycoprotein (Mag), proteolipid protein (Plp), and 2',3'-cyclic nucleotide 3'-phosphodiesterase (Cnp). T3 is not only a triggering signal for oligodendrocyte differentiation, but it has continuous stimulatory effects on myelin gene expression. Transcription in isolated nuclei experiments shows that T3 increases Mag and Cnp transcription rates. After inhibiting transcription with actinomycin D, we measured the half-lives of specific mRNAs. Our results show that T3 increases the stability of mRNA for myelin basic protein, and probably proteolipid protein. In vitro translation followed by myelin basic protein-specific immunoprecipitation showed a direct stimulatory effect of T3 on myelin basic protein mRNA translation. Moreover, this stimulation was higher when the mRNA was already stabilized in culture, indicating that stabilization is achieved through mRNA structural modifications. These results demonstrate the diverse and multiple mechanisms of T3 stimulation of myelin protein genes.

Association between protein feeding and reproductive efficiency in the dairy cow : specific emphasis on protein feeding in Finland

Selostus: Lypsylehmien valkuaisruokinnan ja hedelmällisyyden yhteys: kirjallisuustutkimus valkuaisruokinnan vaikutuksista Suomen olosuhteissa

"Peptabody": a new type of high avidity binding protein.

A new type of high avidity binding molecule, termed "peptabody" was created by harnessing the effect of multivalent interaction. A short peptide ligand was fused via a semi-rigid hinge region with the coiled-coil assembly domain of the cartilage oligomeric matrix protein, resulting in a pentameric multivalent binding molecule. In the first peptabody (Pab-S) described here, a peptide (S) specific for the mouse B-cell lymphoma BCL1 surface Ig idiotype, was selected from a phage display library. A fusion gene was constructed encoding peptide S, followed by the 24 aa hinge region from camel IgG and a modified 55 aa cartilage oligomeric matrix protein pentamerization domain. The Pab-S fusion protein was expressed in Escherichia coli in a soluble form at high levels and purified in a single step by metal-affinity chromatography. Pab-S specifically bound the BCL1 surface idiotype with an avidity of about 1 nM, which corresponds to a 2 x 10(5)-fold increase compared with the affinity of the synthetic peptide S itself. Biochemical characterization showed that Pab-S is a stable homopentamer of about 85 kDa, with interchain disulfide bonds. Pab-S can be dissociated under denaturing and reducing conditions and reassociated as a pentamer with full-binding activity. This intrinsic feature provides an easy way to combine Pab molecules with two different peptide specificities, thus producing heteropentamers with bispecific and/or chelating properties.

Human epidermal Langerhans cells express the tight junction protein claudin-1 and are present in human genetic claudin-1 deficiency (NISCH syndrome).

Claudin-1 (CLDN1) is a structural tight junction (TJ) protein and is expressed in differentiating keratinocytes and Langerhans cells in the epidermis. Our objective was to identify immunoreactive CLDN1 in human epidermal Langerhans cells and to examine the pattern of epidermal Langerhans cells in genetic human CLDN1 deficiency [neonatal ichthyosis, sclerosing cholangitis (NISCH) syndrome]. Epidermal cells from healthy human skin labelled with CLDN1-specific antibodies were analysed by confocal laser immunofluorescence microscopy and flow cytometry. Skin biopsy sections of two patients with NISCH syndrome were stained with an antibody to CD1a expressed on epidermal Langerhans cells. Epidermal Langerhans cells and a subpopulation of keratinocytes from healthy skin were positive for CLDN1. The gross number and distribution of epidermal Langerhans cells of two patients with molecularly confirmed NISCH syndrome, however, was not grossly altered. Therefore, CLDN1 is unlikely to play a critical role in migration of Langerhans cells (or their precursors) to the epidermis or their positioning within the epidermis. Our findings do not exclude a role of this TJ molecule once Langerhans cells have left the epidermis for draining lymph nodes.