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miR-185 is a microRNA (miR) that targets Bruton's tyrosine kinase in B cells, with reductions in miR-185 linked to B cell autoantibody production. In hippocampal neurons, miR-185 targets both sarcoplasmic/endoplasmic reticulum calcium ATPase 2 and a novel Golgi inhibitor. This miR is haploinsufficient in 90–95% of individuals with chromosome 22q11.2 deletion syndrome, patients who can present with immune, cardiac, and parathyroid problems, learning disorders, and a high incidence of schizophrenia in adults. The reduced levels of miR-185 in neurons cause presynaptic neurotransmitter release. Many of the 22q11.2 deletion syndrome patients have a thymic hypoplasia, which results in a peripheral T cell lymphopenia and unusual T helper cell skewing. The molecular targets of miR-185 in thymocytes are unknown. Using an miR-185 T cell transgenic approach, increasing levels of miR-185 attenuated T cell development at the T cell receptor β (TCRβ) selection checkpoint and during positive selection. This caused a peripheral T cell lymphopenia. Mzb1, Nfatc3, and Camk4 were identified as novel miR-185 targets. Elevations in miR-185 enhanced TCR-dependent intracellular calcium levels, whereas a knockdown of miR-185 diminished these calcium responses. These effects concur with reductions in Mzb1, an endoplasmic reticulum calcium regulator. Consistent with their haploinsufficiency of miR-185, Mzb1 levels were elevated in thymocyte extracts from several 22q11.2 deletion syndrome patients. Our findings indicate that miR-185 regulates T cell development through its targeting of several mRNAs including Mzb1. Background: MicroRNAs have critical roles in T cell development under normal and stress conditions. Results: Increasing miR-185 levels attenuate T cell development via the targeting of Mzb1, Nfatc3, and Camk4. Conclusion: Elevations in miR-185 impair thymopoiesis at several developmental stages. Significance: miR-185 levels are reduced in 22q11.2 deletion syndrome patients and the identification of its gene targets is clinically informative.

Physiological stress resulting from infections, trauma, surgery, alcoholism, malnutrition, and/or pregnancy results in a substantial depletion of immature CD4(+)CD8(+) thymocytes. We previously identified 18 distinct stress-responsive microRNAs (miRs) in the thymus upon systemic stress induced by lipopolysaccharide (LPS) or the synthetic glucocorticoid, dexamethasone (Dex). MiRs are short, non-coding RNAs that play critical roles in the immune system by targeting diverse mRNAs, suggesting that their modulation in the thymus in response to stress could impact thymopoiesis. MiR-181d is one such stress-responsive miR, exhibiting a 15-fold down-regulation in expression. We utilized both transgenic and gene-targeting approaches to study the impact of miR-181d on thymopoiesis under normal and stress conditions. The over-expression of miR-181d in developing thymocytes reduced the total number of immature CD4(+)CD8(+) thymocytes. LPS or Dex injections caused a 4-fold greater loss of these cells when compared with the wild type controls. A knockout mouse was developed to selectively eliminate miR-181d, leaving the closely spaced and contiguous family member miR-181c intact. The targeted elimination of just miR-181d resulted in a thymus stress-responsiveness similar to wild-type mice. These experiments suggest that one or more of three other miR-181 family members have overlapping or compensatory functions. Gene expression comparisons of thymocytes from the wild type versus transgenic mice indicated that miR-181d targets a number of stress, metabolic, and signaling pathways. These findings demonstrate that selected miRs enhance stress-mediated thymic involution in vivo.

The papers of this thesis are not available in Munin: 1. Aarbakke, O. N. S., Bucklin, A., Halsband, C. and Norrbin, F.: 'Discovery of Pseudocalanus moultoni Frost 1989 in Northeast Atlantic waters based on mitochondrial COI sequence variation', Journal of Plankton Research (2011), vol. 33(10):1487-1495, availble at http://dx.doi.org/10.1093/plankt/fbr057 2. Aarbakke, O. N. S., Weydmann, A. and Fevolden, S-E.: 'Pseudocalanus (Copepoda: Calanoida) species distribution and relative abundance as indicators of changing sea temperature. Submitted to Journal of Plankton Research' (manuscript) 3. Aarbakke, O., Bucklin, A., Halsband, C. and Norrbin, F.: 'Comparative phylogeography and demographic history of five sibling copepod species in the North Atlantic Ocean' (manuscript) The seven species of the genus Pseudocalanus (Copepoda: Calanoida) are difficult to identify because of very small interspecific, and comparatively large intraspecific, divergence of morphologic and morphometric traits. Thus, despite the fact that Pseudocalanus spp. are among the most abundant metazoans in the world, our knowledge of them at the species level is limited. The main objective of this thesis was to lay the groundwork for future studies of Pseudocalanus spp. in the Northeast Atlantic Ocean and Euro-Arctic by determining which species are present. Through a combined DNA barcoding and traditional identification approach, this work reveals the presence of at least four species of Pseudocalanus, one of which was previously not believed to occur in the East Atlantic Ocean. Furthermore, the thesis reveals differences in environmental preferences and distributions of Pseudocalanus elongatus, P. minutus, P. moultoni and P. acuspes in the Northeast Atlantic Ocean and Euro-Arctic, and discusses implications of these differences in relation to rising sea temperatures. Finally, this work examines the phylogeography and demographic history of Pseudocalanus minutus, P. moultoni, P. elongatus, P. acuspes and P. newmani in the North Atlantic Ocean and based on these results suggests an evolutionary hypothesis for the divergence of Pseudocalanus spp. into one oceanic and one coastal clade. Hopefully, this thesis has achieved its main goal of providing a basis from which the biology and ecology of these fascinating copepod species can be further explored.

Two families of protein tyrosine kinases (PTKs), the Src and Syk/ZAP-70 families, are required for T cell development. Lck is the major Src family member required for thymopoiesis, since there is a severe deficit of CD4 + CD8 + thymocytes and mature T cells in its absence. However, some peripheral T cells are evident in these mice, suggesting that additional PTKs may contribute to T cell development. Here we show that the combined disruption of Lck and Fyn ( lck −/− fyn −/− ) completely arrests αβ T cell development at the CD4 − CD8 − stage. The development of Vγ3 + dendritic epidermal T cells is also severely impaired, but natural killer cell development and cytolytic activity is unaffected in lck −/− fyn −/− mice. These findings reveal the potential for redundant functions mediated by Src family PTKs while emphasizing crucial roles for Lck and Fyn in T cell development.

A set of aromatic, aliphatic and α,β-unsaturated aldehydes has been asymmetrically trimethylsilylcyanated with e.e.'s ranging from 40% to 80% using a chiral (salen)Ti(IV) catalyst prepared in situ from titanium tetraisopropoxide and (1R,2R)[N,N′-bis(2′-hydroxy-3′-t-butyl-benzylidene)]-1,2-diaminocyclohexane or (1R,2R)-[N,N′-bis(2′-hydroxybenzylidene)]-1,2-diaminocyclohexane.

The T- and B-cell receptor (TCR and BCR) signal tranduction processes involve a coordinated interplay between two classes of non-receptor protein tyrosine kinases (PTKs), the Src-family and the Syk/ZAP-70 family of PTKs. Following antigen-receptor stimulation, the Src-family of PTKs mediate the phosphorylation of tyrosine residues contained in a signalling motif localized in the TCR and BCR subunits. The phosphorylation of this signalling motif recruits the Syk/ZAP-70 family of PTKs into the antigen receptor complex. This mechanism requires the tandem SH2 domains in ZAP-70 complexing to two critically spaced phosphotyrosine residues within the signalling motif. The clustering of Syk/ZAP-70 and cross-talk between this family and the Src-PTKs regulates subsequent signalling events that lead to a variety of cellular responses, such as antibody secretion, lymphokine production, cytolytic activity, proliferation, differentiation and cell survival.

Stereoselectivity of aldol reactions between aliphatic aldehydes and Ni(II)-complex of chiral non-racemic Schiff base of glycine with ( S )- o -[ N -( N -benzylprolyl)amino]benzophenone (BPB) in the presence of excess of MeONa, has been studied as a function of time, reaction conditions and nature of an aldehyde. Two salient features of the reaction, very high pseudokinetic syn -(2 S )-diastereoselectivity, and dependence of thermodynamic syn -(2 R )-diastereoselectivity on the steric bulk of an aldehyde side chain, were disclosed and used for efficient (more than 90% de and ee) asymmetric synthesis of both syn -(2 S ) and syn -(2 R )-3-alkyl substituted serines. Synthetic potential and reliability of this asymmetric method are demonstrated with the large scale (2–20 g) preparation of enantiomerically pure amino acids.

T cells are a critical component of the adaptive immune system, developing within the thymus. Immature thymocytes interact with an interconnected meshwork of thymic epithelial cells (TECs) to establish the T cell repertoire. The developmental process is extremely stress sensitive, as the thymus can undergo a rapid involution in response to diverse inflammatory conditions, and a more prolonged hypoplasia during aging. The type of stress predicates whether TECs, thymocytes, and/or myeloid cell populations are affected. Several microRNAs (miRs) have been identified in the thymus based on their ability to mitigate the stress damage. We identified miR-205 as a stress responsive miR specifically expressed in TECs. Mice generated with a conditional ablation of miR-205 in TECs exhibit an age and sex-dependent thymic hypoplasia beginning at 8 weeks. Under stress conditions involving a type I interferon response (dsRNA mimic; polyI:C), the TEC-miR-205 deficient mice had a severe thymic atrophy compared to littermate controls. The TEC-miR-205 deficient mice displayed a delayed recovery of single positive CD4 and CD8 thymocytes, likely resulting from a block in the cortical TEC expansion. qPCR and gene expression comparisons revealed that the miR-205 deficient TECs had significant changes in chemokine/chemokine receptor and antigen processing pathways. MiR-205 positively regulated Foxn1 transcription factor expression, the master regulator of TEC development and function. Interestingly, miR-205 is encoded within a long non-coding RNA (lncRNA), 4631405K08Rik. Current experiments will reveal the mechanisms by which the miR and lncRNA are transcriptionally regulated, and how these affect Foxn1 expression to support thymopoiesis.

Mycobacterium tuberculosis (Mtb) presently infects 1/3 of the World’s population, causing both active and latent pulmonary tuberculosis (TB). The pathogenic mechanisms used by Mtb remain poorly defined. We used a small RNA sequencing strategy on RNA extracted from Mtb-infected THP-1 macrophages to characterize the changes in eukaryotic microRNAs (miRs) and identify any mycobacterially-encoded small RNAs. A large number of mammalian microRNAs were differentially regulated during the infection course. Target prediction programs indicated that the mRNAs regulated by the miRs were involved in immune processes, metabolic pathways, cell communication, and developmental events. In addition, 35 Mtb-encoded small RNAs (18–30 nucleotides, mRs) were discovered. Several of the Mtb-encoded mRs were detected in lung tissue biopsies from TB infected monkeys. The 100–150 nucleotides surrounding the 35 Mtb-encoded small RNAs had extensive secondary RNA folding capabilities, including hairpins and antisense stretches more characteristic of eukaryotic pre-microRNAs. Two such small RNAs, Mtb-mR-1 and Mtb-mR-6 were transcribed in Mycobacterium avium complex and Mtb in a hairpin loop and antisense sequence-dependent manner. These mRs were not expressed in Mycobacterium smegmatis, revealing a restricted expression to pathogenic strains. Mtb-encoded mR-1 and mR-6 modulated both prokaryotic and eukaryotic gene expression. Taken together, our findings reveal potentially novel pathogenic processes utilized by Mtb during infections.

Mycobacterial shuttle vectors contain dual origins of replication for growth in both Escherichia coli and mycobacteria. One such vector, pSUM36, was re-engineered for high-level protein expression in diverse bacterial species. The modified vector (pSUM- kan -MCS2) enabled green fluorescent protein expression in E. coli , Mycobacterium smegmatis , and M. avium at levels up to 50-fold higher than that detected with the parental vector, which was originally developed with a lacZ α promoter. This high-level fluorescent protein expression allowed easy visualization of M. smegmatis and M. avium in infected macrophages. The M. tuberculosis gene esat-6 was cloned in place of the green fluorescence protein gene ( gfp ) to determine the impact of ESAT-6 on the innate inflammatory response. The modified vector (pSUM- kan -MCS2) yielded high levels of ESAT-6 expression in M. smegmatis . The ability of ESAT-6 to suppress innate inflammatory pathways was assayed with a novel macrophage reporter cell line, designed with an interleukin-6 (IL-6) promoter-driven GFP cassette. This stable cell line fluoresces in response to diverse mycobacterial strains and stimuli, such as lipopolysaccharide. M. smegmatis clones expressing high levels of ESAT-6 failed to attenuate IL-6-driven GFP expression. Pure ESAT-6, produced in E. coli , was insufficient to suppress a strong inflammatory response elicited by M. smegmatis or lipopolysaccharide, with ESAT-6 itself directly activating the IL-6 pathway. In summary, a pSUM-protein expression vector and a mammalian IL-6 reporter cell line provide new tools for understanding the pathogenic mechanisms deployed by various mycobacterial species.

The T cell receptor (TCR) comprises an antigen-specific alpha beta heterodimer non-covalently associated with the CD3 gamma delta epsilon and TCR zeta subunits. Both the CD3 and TCR zeta subunits are proposed to be responsible for the intracellular signal-transduction events. We report here the production of eight monoclonal antibodies (mAbs) that bind in an ELISA assay to a 113 amino acid synthetic peptide corresponding to the cytoplasmic domain of TCR zeta. Western blot analysis of anti-CD8 precipitates of lysates of transfectants expressing chimeric CD8/zeta constructs encoding increasing COOH-terminal truncations of TCR zeta indicates that four of these mAbs recognized the region of TCR zeta chain comprising the last 29 COOH-terminal residues. Thus, this region of TCR theta may encode an immunodominant epitope. Furthermore, one of these mAbs, G3, is capable of precipitating both non-phosphorylated and tyrosine phosphorylated TCR zeta. The G3 mAb should be useful for elucidating the structural and signalling characteristics of the TCR zeta chain.

A new approach to the asymmetric synthesis of β-substituted α-aminopropanoic acids by 2,2′-azoisobutyronitrile (AIBN) and Bu3SnH-initiated radical addition of Etl, PriBr, ButBr, and PhCH2Br to the dehydroalanine moiety of the NiII complex 1 of a Schiff′s base derived from (S)-o-[N-(N′-benzylprolyl)amino]benzophenone (BPB) and dehydroalanine is described. The radical addition produced a mixture of diastereoisomeric complexes 4a–d with a 40–90% excess of (S,S)diastereoisomers over the (S,R)-ones, giving the reaction products in almost quantitative yields. The diastereoselectivity of the reaction depended on the size of the entering radicals, the most effective asymmetric induction being achieved for the But radical addition. Enantiomerically pure ‘(S)-2-amino3-(tert-butyl)propanoic acid’[(S)-γ-methylleucine] and the chiral auxiliary BPB were recovered from compound 4d after its decomposition with HCl. The reactivities of the carbon–centred radicals towards the carbon-carbon double bond in the amino acid moiety of the complex 1 was quantitatively established by using ESR spectroscopy in the spin-trap technique.

BackgroundPhysiological stress evokes rapid changes in both the innate and adaptive immune response. Immature αβ T cells developing in the thymus are particularly sensitive to stress, with infections and/or exposure to lipopolysaccharide or glucocorticoids eliciting a rapid apoptotic program. MicroRNAs are a class of small, non-coding RNAs that regulate global gene expression by targeting diverse mRNAs for degradation. We hypothesized that a subset of thymically encoded microRNAs would be stress responsive and modulate thymopoiesis. We performed microRNA profiling of thymic microRNAs isolated from control or stressed thymic tissue obtained from mice. We identified 18 microRNAs that are dysregulated >1.5-fold in response to lipopolysaccharide or the synthetic corticosteroid dexamethasone. These included the miR-17-90 cluster, which have anti-apoptotic functions, and the miR-181 family, which contribute to T cell tolerance. The stress-induced changes in the thymic microRNAs are dynamically and distinctly regulated in the CD4(-)CD8(-), CD4(+)CD8(+), CD4(+)CD8(-), and CD4(-)CD8(+) thymocyte subsets. Several of the differentially regulated murine thymic miRs are also stress responsive in the heart, kidney, liver, brain, and/or spleen. The most dramatic thymic microRNA down modulated is miR-181d, exhibiting a 15-fold reduction following stress. This miR has both similar and distinct gene targets as miR-181a, another member of miR-181 family. Many of the differentially regulated microRNAs have known functions in thymopoiesis, indicating that their dysregulation will alter T cell repertoire selection and the formation of naïve T cells. This data has implications for clinical treatments involving anti-inflammatory steroids, ablation therapies, and provides mechanistic insights into the consequences of infections.

The CD3ε cytoplasmic tail contains a conserved proline-rich sequence (PRS) that influences TCR–CD3 expression and signaling. Although the PRS can bind the SH3.1 domain of the cytosolic adapter Nck, whether the PRS is constitutively available for Nck binding or instead represents a cryptic motif that is exposed via conformational change upon TCR–CD3 engagement (CD3Δc) is currently unresolved. Furthermore, the extent to which a cis-acting CD3ε basic amino acid-rich stretch (BRS), with its unique phosphoinositide-binding capability, might impact PRS accessibility is not clear. In this study, we found that freshly harvested primary thymocytes expressed low to moderate basal levels of Nck-accessible PRS (“open-CD3”), although most TCR–CD3 complexes were inaccessible to Nck (“closed-CD3”). Ag presentation in vivo induced open-CD3, accounting for half of the basal level found in thymocytes from MHC+ mice. Additional stimulation with either anti-CD3 Abs or peptide–MHC ligands further elevated open-CD3 above basal levels, consistent with a model wherein antigenic engagement induces maximum PRS exposure. We also found that the open-CD3 conformation induced by APCs outlasted the time of ligand occupancy, marking receptors that had been engaged. Finally, CD3ε BRS–phosphoinositide interactions played no role in either adoption of the initial closed-CD3 conformation or induction of open-CD3 by Ab stimulation. Thus, a basal level of open-CD3 is succeeded by a higher, induced level upon TCR–CD3 engagement, involving CD3Δc and prolonged accessibility of the CD3ε PRS to Nck.

Benzaldehyde has been asymmetrically trimethylsilylcyanated, using chiral (salen)Ti(IV) catalysts 1a and 1b, 2a and 2b, 3a and 3b prepared in situ from titanium tetraisopropoxide and the Schiff's bases derived from (R)- or (S)-4-hydroxy-5-formyl[2.2]paracyclophane [(R)- and (S)-FHPC] and diaminoethane (EDA) (catalysts 1a or 1b); (R)- or (S)-FHPC and 1,3-diaminopropane (PDA) (catalysts 2a or 2b); (R)- or (S)-FHPC and (1R,2R)-1,2-diaminocyclohexane [(1R,2R)-CHDA] (catalysts 3a and 3b). Surprisingly, 1a and 1b were found to be the most efficient catalysts whereas both enantiomers of 2 were completely inactive. The maximum e.e. of 84% (S) at −78°C was obtained in the reaction catalysed by 1b at 5–10 mol%. The catalyst could be precipitated with hexane from the reaction mixture and reused.

A bimetallic titanium(IV)salen complex has been developed as an exceptionally active catalyst for the asymmetric addition of trimethylsilyl cyanide to ketones. For the corresponding addition to aldehydes, a vanadium(IV)salen complex was found to give higher levels of asymmetric induction. In both cases, additional evidence in support of the proposed catalytic cycle is presented.

Invariant NKT (iNKT) cells regulate early immune responses to infections, in part because of their rapid release of IFN-γ and IL-4. iNKT cells are proposed to reduce the severity of Lyme disease following Borrelia burgdorferi infection. Unlike conventional T cells, iNKT cells express an invariant αβ TCR that recognizes lipids bound to the MHC class I-like molecule, CD1d. Furthermore, these cells are positively selected following TCR interactions with glycolipid/CD1d complexes expressed on CD4+CD8+ thymocytes. Whereas conventional T cell development can proceed with as few as 4/10 CD3 immunoreceptor tyrosine-based activation motifs (ITAMs), little is known about the ITAM requirements for iNKT cell selection and expansion. We analyzed iNKT cell development in CD3 ζ transgenic lines with various tyrosine-to-phenylalanine substitutions (YF) that eliminated the functions of the first (YF1,2), third (YF5,6), or all three (YF1–6) CD3 ζ ITAMs. iNKT cell numbers were significantly reduced in the thymus, spleen, and liver of all YF mice compared with wild type mice. The reduced numbers of iNKT cells resulted from significant reductions in the expression of the early growth response 2 and promyelocytic leukemia zinc finger transcription factors. In the mice with few to no iNKT cells, there was no difference in the severity of Lyme arthritis compared with wild type controls, following infections with the spirochete B. burgdorferi. These findings indicate that a full complement of functional CD3 ζ ITAMs is required for effective iNKT cell development.

A (salen)titanium catalyst has been found to induce the asymmetric addition of potassium cyanide and acetic anhydride to aldehydes, giving enantiomerically enriched cyanohydrin esters with up to 92% enantiomeric excess using just 1 mol% of the catalyst. This is the first report of the asymmetric synthesis of cyanohydrin derivatives using a cyanide source which is non-volatile and inexpensive.

Transgenic mice bearing the alpha beta transgenes encoding a defined T cell receptor specific for the male (H-Y) antigen presented by the H-2Db class I MHC molecule were used to study mechanisms of peripheral tolerance. Female transgenic mice produce large numbers of functionally homogeneous CD8+ male antigen-reactive T cells in the thymus that subsequently accumulate in the peripheral lymphoid organs. We have used three experimental approaches to show that male reactive CD8+ T cells can be eliminated from peripheral lymphoid organs after exposure to male antigen. (i) In female transgenic mice that were neonatally tolerized with male spleen cells, male reactive CD8+ T cells continued to be produced in large numbers in the thymus but were virtually absent in the lymph nodes. (ii) Injection of thymocytes from female transgenic mice into female mice neonatally tolerized with the male antigen, or into normal male mice, led to the specific elimination of male-reactive CD8+ T cells in the lymph nodes. (iii) Four days after male lymphoid cells were injected intravenously into female transgenic mice, male antigen-reactive CD8+ T cells recovered from the lymph nodes of recipient mice were highly apoptotic when compared to CD4+ (non-male reactive) T cells. These data indicate that tolerance to extrathymic antigen can be achieved through elimination of mature T cells in the peripheral lymphoid organs.

The CD3 ε subunit of the TCR complex contains two defined signaling domains, a proline-rich sequence and an ITAM. We identified a third signaling sequence in CD3 ε, termed the basic-rich stretch (BRS). Herein, we show that the positively charged residues of the BRS enable this region of CD3 ε to complex a subset of acidic phospholipids, including PI(3)P, PI(4)P, PI(5)P, PI(3,4,5)P3, and PI(4,5)P2. Transgenic mice containing mutations of the BRS exhibited varying developmental defects, ranging from reduced thymic cellularity to a complete block in T cell development. Peripheral T cells from BRS-modified mice also exhibited several defects, including decreased TCR surface expression, reduced TCR-mediated signaling responses to agonist peptide-loaded APCs, and delayed CD3 ε localization to the immunological synapse. Overall, these findings demonstrate a functional role for the CD3 ε lipid-binding domain in T cell biology.

Temporal and spatial variations in the concentrations of signaling intermediates in a living cell are important for signaling in complex networks because they modulate the probabilities that signaling intermediates will interact with each other. We have studied 30 signaling sensors, ranging from receptors to transcription factors, in the physiological activation of murine ex vivo T cells by antigen-presenting cells. Spatiotemporal patterning of these molecules was highly diverse and varied with specific T cell receptors and T cell activation conditions. The diversity and variability observed suggest that spatiotemporal patterning controls signaling interactions during T cell activation in a physiologically important and discriminating manner. In support of this, the effective clustering of a group of ligand-engaged receptors and signaling intermediates in a joint pattern consistently correlated with efficient T cell activation at the level of the whole cell.

The LspA proteins (LspA1 and LspA2) of Haemophilus ducreyi are necessary for this pathogen to inhibit the phagocytic activity of macrophage cell lines, an event that can be correlated with a reduction in the level of active Src family protein tyrosine kinases (PTKs) in these eukaryotic cells. During studies investigating this inhibitory mechanism, it was discovered that the LspA proteins themselves were tyrosine phosphorylated after wild-type H. ducreyi cells were incubated with macrophages. LspA proteins in cell-free concentrated H. ducreyi culture supernatant fluid could also be tyrosine phosphorylated by macrophages. This ability to tyrosine phosphorylate the LspA proteins was not limited to immune cell lineages but could be accomplished by both HeLa and COS-7 cells. Kinase inhibitor studies with macrophages demonstrated that the Src family PTKs were required for this tyrosine phosphorylation activity. In silico methods and site-directed mutagenesis were used to identify EPIYG and EPVYA motifs in LspA1 that contained tyrosines that were targets for phosphorylation. A total of four tyrosines could be phosphorylated in LspA1, with LspA2 containing eight predicted tyrosine phosphorylation motifs. Purified LspA1 fusion proteins containing either the EPIYG or EPVYA motifs were shown to be phosphorylated by purified Src PTK in vitro. Macrophage lysates could also tyrosine phosphorylate the LspA proteins and an LspA1 fusion protein via a mechanism that was dependent on the presence of both divalent cations and ATP. Several motifs known to interact with or otherwise affect eukaryotic kinases were identified in the LspA proteins.

T cell receptor signaling processes are controlled by the integrated actions of families of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPases). Several distinct cytosolic protein tyrosine phosphatases have been described that are able to negatively regulate TCR signaling pathways, including SHP-1, SHP-2, PTPH1, and PEP. Using PTPase substrate-trapping mutants and wild type enzymes, we determined that PTPN4/PTP-MEG1, a PTPH1-family member, could complex and dephosphorylate the ITAMs of the TCR zeta subunit. In addition, the substrate-trapping derivative augmented basal and TCR-induced activation of NF-kappaB in T cells. To characterize the contribution of this PTPase in T cells, we developed PTPN4-deficient mice. T cell development and TCR signaling events were comparable between wild type and PTPN4-deficient animals. The magnitude and duration of TCR-regulated ITAM phosphorylation, as well as overall protein phosphorylation, was unaltered in the absence of PTPN4. Finally, Th1- and Th2-derived cytokines and in vivo immune responses to Listeria monocytogenes were equivalent between wild type and PTPN4-deficient mice. These findings suggest that additional PTPases are involved in controlling ITAM phosphorylations.

We provide an example of an outcome game form with two players for which there is in an open set of utilities for both players such that, in each of the associated games, the set of Nash equilibria induce a continuum of outcome distributions. The case for three or more players has been settled by Govindan and McLennan [3].

We provide an example of an outcome game form with two players for which there is in an open set of utilities for both players such that, in each of the associated games, the set of Nash equilibria induce a continuum of outcome distributions. The case for three or more players has been settled by Govindan and McLennan [3].

We developed a procedure to culture microorganisms below freezing point on solid media (cellulose powder or plastic film) with ethanol as the sole carbon source without using artificial antifreezes. Enrichment from soil and permafrost obtained on such frozen solid media contained mainly fungi, and further purification resulted in isolation of basidiomycetous yeasts of the genera Mrakia and Leucosporidium as well as ascomycetous fungi of the genus Geomyces. Contrary to solid frozen media, the enrichment of liquid nutrient solutions at 0 degrees C or supercooled solutions stabilized by glycerol at -1 to -5 degrees C led to the isolation of bacteria representing the genera Polaromonas, Pseudomonas and Arthrobacter. The growth of fungi on ethanol-microcrystalline cellulose media at -8 degrees C was exponential with generation times of 4.6-34 days, while bacteria displayed a linear or progressively declining curvilinear dynamic. At -17 to -0 degrees C the growth of isolates and entire soil community on 14C-ethanol was continuous and characterized by yields of 0.27-0.52 g cell C (g of C-substrate)(-1), similar to growth above the freezing point. The 'state of maintenance,' implying measurable catabolic activity of non-growing cells, was not confirmed. Below -18 to -35 degrees C, the isolated organisms were able to grow only transiently for 3 weeks after cooling with measurable respiratory and biosynthetic (14CO2 uptake) activity. Then metabolic activity declined to zero, and microorganisms entered a state of reversible dormancy.

Haemophilus ducreyi , the etiologic agent of the sexually transmitted disease chancroid, has been shown to inhibit phagocytosis of both itself and secondary targets in vitro. Immunodepletion of LspA proteins from H. ducreyi culture supernatant fluid abolished this inhibitory effect, indicating that the LspA proteins are necessary for the inhibition of phagocytosis by H. ducreyi . Fluorescence microscopy revealed that macrophages incubated with wild-type H. ducreyi , but not with a lspA1 lspA2 mutant, were unable to complete development of the phagocytic cup around immunoglobulin G-opsonized targets. Examination of the phosphotyrosine protein profiles of these two sets of macrophages showed that those incubated with wild-type H. ducreyi had greatly reduced phosphorylation levels of proteins in the 50-to-60-kDa range. Subsequent experiments revealed reductions in the catalytic activities of both Lyn and Hck, two members of the Src family of protein tyrosine kinases that are known to be involved in the proximal signaling steps of Fcγ receptor-mediated phagocytosis. Additional experiments confirmed reductions in the levels of both active Lyn and active Hck in three different immune cell lines, but not in HeLa cells, exposed to wild-type H. ducreyi . This is the first example of a bacte-rial pathogen that suppresses Src family protein tyrosine kinase activity to subvert phagocytic signaling in hostcells.

T cell receptor (TCR) signal transduction is mediated by the immunoreceptor tyrosine-based activation motifs (ITAM). The ten ITAM in the TCR complex are distributed in two distinct signaling modules termed TCR zetazeta and CD3 gammaepsilon/deltaepsilon. To delineate the specific role of the zeta ITAM in T cell development and TCR signal transmission, we compared the properties of T cells from different TCR zeta-transgenic lines wherein tyrosine-to-phenylalanine substitutions had been introduced in the zeta subunit. These lines lack selected phosphorylated forms of TCR zeta including just p23, both p21 and p23, or all phospho-zeta derivatives. We report herein that the efficiency of positive selection in HY TCR-transgenic female mice was directly related to the number of zeta ITAM in the TCR. In contrast, TCR-mediated signal transmission and T cell proliferative responses following agonist peptide stimulation were similar and independent of the zeta ITAM. Only the duration of MAPK activation was affected by multiple zeta ITAM substitutions. These results strongly suggest that the ITAM in the CD3 gammaepsilon/deltaepsilon module can provide normal TCR signal transmission, with zeta ITAM providing a secondary function facilitating MAPK activation and positive selection.