Cortical RORß is required for layer 4 transcriptional identity and barrel integrity.

Retinoic acid-related orphan receptor beta (RORß) is a transcription factor (TF) and marker of layer 4 (L4) neurons, which are distinctive both in transcriptional identity and the ability to form aggregates such as barrels in rodent somatosensory cortex. However, the relationship between transcriptional identity and L4 cytoarchitecture is largely unknown. We find RORß is required in the cortex for L4 aggregation into barrels and thalamocortical afferent (TCA) segregation. Interestingly, barrel organization also degrades with age in wildtype mice. Loss of RORß delays excitatory input and disrupts gene expression and chromatin accessibility, with down-regulation of L4 and up-regulation of L5 genes, suggesting a disruption in cellular specification. Expression and binding site accessibility change for many other TFs, including closure of neurodevelopmental TF binding sites and increased expression and binding capacity of activity-regulated TFs. Lastly, a putative target of RORß, Thsd7a, is down-regulated without RORß, and Thsd7a knock-out alone disrupts TCA organization in adult barrels.

MRI Assessment of Prostate-Specific Membrane Antigen (PSMA) Targeting by a PSMA-Targeted Magnetic Nanoparticle: Potential for Image-Guided Therapy.

Magnetic nanoparticle (MNP)-induced hyperthermia is currently being evaluated for localized prostate cancer. We evaluated the feasibility of tumor-selective delivery of prostate-specific membrane antigen (PSMA)-targeted MNPs in a murine model with high-resolution magnetic resonance imaging (MRI) after intravenous administration of MNPs at a concentration necessary for hyperthermia. A PSMA-targeted MNP was synthesized and evaluated using T2-weighted MRI, after intravenous administration of 50 mg/kg of the MNP. Significant contrast enhancement ( P < 0.0002, n = 5) was observed in PSMA(+) tumors compared to PSMA(-) tumors 24 h and 48 h after contrast agent administration. Mice were also imaged with near-infrared fluorescence imaging, to validate the MRI results. Two-photon microscopy revealed higher vascular density at the tumor periphery, which resulted in higher  peripheral accumulation of PSMA-targeted MNPs. These results suggest that the delivery of PSMA-targeted MNPs to PSMA(+) tumors is both actively targeted and passively mediated.

High affinity sugar ligands of C-type lectin receptor langerin.

BACKGROUND: Langerin, a C-type lectin receptor (CLR) expressed in a subset of dendritic cells (DCs), binds to glycan ligands for pathogen capture and clearance. Previous studies revealed that langerin has an unusual binding affinity toward 6-sulfated galactose (Gal), a structure primarily found in keratan sulfate (KS). However, details and biological outcomes of this interaction have not been characterized. Based on a recent discovery that the disaccharide L4, a KS component that contains 6-sulfo-Gal, exhibits anti-inflammatory activity in mouse lung, we hypothesized that L4-related compounds are useful tools for characterizing the langerin-ligand interactions and their therapeutic application. METHODS: We performed binding analysis between purified long and short forms of langerin and a series of KS disaccharide components. We also chemically synthesized oligomeric derivatives of L4 to develop a new high-affinity ligand of langerin. RESULTS: We show that the binding critically requires the 6-sulfation of Gal and that the long form of langerin displays higher affinity than the short form. The synthesized trimeric (also designated as triangle or Tri) and polymeric (pendant) L4 derivatives displayed over 1000-fold higher affinity toward langerin than monomeric L4. The pendant L4, but not the L4 monomer, was found to effectively transduce langerin signaling in a model cell system. CONCLUSIONS: L4 is a specific ligand for langerin. Oligomerization of L4 unit increased the affinity toward langerin. GENERAL SIGNIFICANCE: These results suggest that oligomeric L4 derivatives will be useful for clarifying the langerin functions and for the development of new glycan-based anti-inflammatory drugs.

Nonpyrogenic Molecular Adjuvants Based on norAbu-Muramyldipeptide and norAbu-Glucosaminyl Muramyldipeptide: Synthesis, Molecular Mechanisms of Action, and Biological Activities in Vitro and in Vivo.

Fatty acyl analogues of muramyldipeptide (MDP) (abbreviated N-L18 norAbuGMDP, N-B30 norAbuGMDP, norAbuMDP-Lys(L18), norAbuMDP-Lys(B30), norAbuGMDP-Lys(L18), norAbuGMDP-Lys(B30), B30 norAbuMDP, L18 norAbuMDP) are designed and synthesized comprising the normuramyl-l-α-aminobutanoyl (norAbu) structural moiety. All new analogues show depressed pyrogenicity in both free (micellar) state and in liposomal formulations when tested in rabbits in vivo (sc and iv application). New analogues are also shown to be selective activators of NOD2 and NLRP3 (inflammasome) in vitro but not NOD1. Potencies of NOD2 and NLRP3 stimulation are found comparable with free MDP and other positive controls. Analogues are also demonstrated to be effective in stimulating cellular proliferation when the sera from mice are injected sc with individual liposome-loaded analogues, causing proliferation of bone marrow-derived GM-progenitors cells. Importantly, vaccination nanoparticles prepared from metallochelation liposomes, His-tagged antigen rOspA from Borrelia burgdorferi, and lipophilic analogue norAbuMDP-Lys(B30) as adjuvant, are shown to provoke OspA-specific antibody responses with a strong Th1-bias (dominance of IgG2a response). In contrast, the adjuvant effects of Alum or parent MDP show a strong Th2-bias (dominance of IgG1 response).

Plumbagin-loaded aptamer-targeted poly D,L-lactic-co-glycolic acid-b-polyethylene glycol nanoparticles for prostate cancer therapy.

Plumbagin inhibits the growth, metastasis, and invasion of prostate cancer (PCa). However, its lower bioavailability limits biopharmaceutical properties due to insolubility in water. Prostate-specific membrane antigen (PSMA) aptamer-targeted nanoparticles (NPs) significantly enhanced cytotoxicity in prostate epithelial cells. This study aimed to investigate the effects of plumbagin-loaded prostate-specific membrane antigen (PSMA) aptamer-targeted poly D,L-lactic-co-glycolic acid-b-polyethylene glycol (PLGA-PEG) nanoparticles (NPs) on prostate cancer (PCa) in vitro.PLGA-PEG with a terminal carboxylic acid group (PLGA-PEG-COOH) was synthesized, and plumbagin was loaded on PLGA-PEG-COOH NPs using the nanoprecipitation method and characterized by field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and laser light scattering. The uptake and distribution of plumbagin-NPs in human PCa LNCaP cells were investigated by fluorescent labeling. Subsequently, PSMA antibody-targeted PLGA-PEG-COOH NPs (targeted NPs) were prepared by covalent binding and characterized by x-ray photoelectron spectroscopy. Furthermore, the anticancer activity of plumbagin-loaded, targeted NPs was compared with that of nontargeted NPs in LNCaP cells in vitro.Plumbagin-NPs (diameter of 189.4 ±â€Š30.6 nm and zeta potential of -17.1 ±â€Š3.7 mV) were optimized based on theoretical drug loading of 5% and a ratio of water:acetone of 3:1. During the first 2 hours, the cumulative release rate of the drug was 66.4 ±â€Š8.56%. Moreover, plumbagin-targeted NPs with nitrogen atoms were prepared. The uptake rate was 90% at 0.5 hours for targeted and nontargeted NPs. The IC50 of targeted NPs and nontargeted NPs was 32.59 ±â€Š8.03 µM and 39.02 ±â€Š7.64 µM, respectively.Plumbagin-loaded PSMA aptamer-targeted NPs can be used in targeted chemotherapy against PCa.

Optimization of Labeling PSMAHBED with Ethanol-Postprocessed 68Ga and Its Quality Control Systems.

Radiolabeling of the prostate-specific membrane antigen (PSMA) inhibitor Glu-NH-CO-NH-Lys(Ahx) using the 68Ga chelator HBED-CC (PSMAHBED) allows imaging of prostate cancer lesions because of high expression of PSMA in prostate carcinoma cells and in bone metastases and lymph nodes related to the disease. The aim of this work was to optimize labeling of 68Ga-PSMAHBED using the efficient cation-exchange postprocessing of 68Ga as well as the development of a thin-layer chromatography (TLC)-based quality control system. Methods: Labeling was optimized for online ethanol-postprocessed 68Ga eluate investigating various parameters, such as buffer molarity (0.1-1 M), temperature (25°C-90°C), tracer amount (0.11-0.74 nmol), and labeling time. In addition, purification of the crude product was tested. For radio-TLC quality control, various mobile phases were analyzed using silica gel 60 plates and the results were validated using high-performance liquid chromatography. The most superior mobile phases were also applied on instant thin-layer chromatography (ITLC) silica gel plates. Results: Using optimized conditions, labeling yields of more than 95% were obtained within 10 min when ethanol-based postprocessing was applied using PSMAHBED amounts as low as 0.1 nmol. A higher precursor concentration (0.7 nmol) further increased labeling and quantitative yields to more than 98% within 5 min. In clinical routine, patient batches (>200 applications) with radiochemical purity greater than 98% and specific activities of 326 ± 20 MBq/nmol are obtained reproducibly. When TLC quality control was performed on silica gel 60 plates, 4 mobile phases with suitable separation properties and complementary Rf values were identified. Two systems showed equivalent separation on ITLC silica gel plates, with ITLC analysis finished within 5 min, in contrast to 20 min for the TLC system. Labeling of PSMAHBED was optimized for cation-exchange postprocessing methods, ensuring almost quantitative labeling and high nuclide purity of final 68Ga-PSMAHBED, making subsequent purification steps unnecessary. Conclusion: The new radio-TLC method allows quality control in a short time using a fast, reliable, low-cost method with little equipment complexity. Using this approach, the synthesis is easily adopted by automated synthesis modules.

Development of a complementary PET/MR dual-modal imaging probe for targeting prostate-specific membrane antigen (PSMA).

We tried to develop a dual-modal PET/MR imaging probe using a straightforward one-pot method by encapsulation with specific amphiphiles. In this study, iron oxide (IO) nanoparticles were encapsulated with three amphiphiles containing PEG, DOTA and the prostate-specific membrane antigen (PSMA)-targeting ligand in aqueous medium. The diameter of the prepared nanoparticle DOTA-IO-GUL was 11.01±1.54nm. DOTA-IO-GUL was labeled with (68)Ga in high efficiency. The DOTA-IO-GUL showed a dose-dependent binding to LNCaP (PSMA positive) cells via a competitive binding study against (125)I-labeled MIP-1072 (PSMA-targeting agent). Additionally, PET and MR imaging results showed PSMA selective uptake by only 22Rv1 (PSMA positive) but not PC-3 (PSMA negative) in dual-tumor xenograft mouse model study. MR imaging showed high resolution, and PET imaging enabled quantification and confirmation of the specificity. In conclusion, we have successfully developed the specific PSMA-targeting IO nanoparticle, DOTA-IO-GUL, as a dual-modality probe for complementary PET/MR imaging. FROM THE CLINICAL EDITOR: The combination of using Positron Emission Tomography (PET) and computed tomography (CT) in clinical practice is now the norm. With advances in technology, the next step would be to develop combined PET and Magnetic Resonance (MR) dual-imaging. In this article, the authors described their positive study on the development of a dual-modal PET/MR imaging probe using a prostate cancer model.

Identification and mechanistic characterization of low-molecular-weight inhibitors for HuR.

Careful regulation of mRNA half-lives is a fundamental mechanism allowing cells to quickly respond to changing environmental conditions. The mRNA-binding Hu proteins are important for stabilization of short-lived mRNAs. Here we describe the identification and mechanistic characterization of the first low-molecular-weight inhibitors for Hu protein R (HuR) from microbial broths (Actinomyces sp.): dehydromutactin (1), MS-444 (2) and okicenone (3). These compounds interfere with HuR RNA binding, HuR trafficking, cytokine expression and T-cell activation. A mathematical and experimental analysis of the compounds' mode of action suggests that HuR homodimerizes before RNA binding and that the compounds interfere with the formation of HuR dimers. Our results demonstrate the chemical drugability of HuR; to our knowledge HuR is the first example of a drugable protein within the Hu family. MS-444, dehydromutactin and okicenone may become valuable tools for studying HuR function. An assessment of HuR inhibition as a central node in malignant processes might open up new conceptual routes toward combatting cancer.

Partially assembled K99 fimbriae are required for protection.

Antibodies to K99 fimbriae afford protection to F5+ bovine enterotoxigenic Escherichia coli (ETEC). Previous studies show that murine dams immunized with Salmonella vaccine vectors stably expressing K99 fimbriae confer protection to ETEC-challenged neonatal pups. To begin to address adaptation of the K99 scaffold to display heterologous B- and T-cell epitopes, studies were conducted to determine how much of the assembled K99 fimbria is required to maintain protective immunity. Sequential deletions in the K99 gene clusters were made, resulting in diminished localization of the K99 fimbrial subunit in the outer membrane. As placement of the K99 fimbrial subunit became progressively contained within the vaccine vector, diminished immunoglobulin A (IgA) and IgG1 antibody titers, as well as diminished Th2-type cytokine responses, were observed in orally immunized mice. Deletion of fanGH, which greatly reduced the export of the fimbrial subunit to the outer membrane, showed only partial reduction in protective immunity. By contrast, deletion of fanDEFGH, which also reduced the export of the fimbrial subunit to the outer membrane but retained more subunit in the cytoplasm, resulted in protective immunity being dramatically reduced. Thus, these studies showed that retention of K99 fimbrial subunit as native fimbriae or with the deletion of fanGH is sufficient to confer protection.

Crystal structure of prostate-specific membrane antigen, a tumor marker and peptidase.

Prostate-specific membrane antigen (PSMA) is highly expressed in prostate cancer cells and nonprostatic solid tumor neovasculature and is a target for anticancer imaging and therapeutic agents. PSMA acts as a glutamate carboxypeptidase (GCPII) on small molecule substrates, including folate, the anticancer drug methotrexate, and the neuropeptide N-acetyl-l-aspartyl-l-glutamate. Here we present the 3.5-A crystal structure of the PSMA ectodomain, which reveals a homodimer with structural similarity to transferrin receptor, a receptor for iron-loaded transferrin that lacks protease activity. Unlike transferrin receptor, the protease domain of PSMA contains a binuclear zinc site, catalytic residues, and a proposed substrate-binding arginine patch. Elucidation of the PSMA structure combined with docking studies and a proposed catalytic mechanism provides insight into the recognition of inhibitors and the natural substrate N-acetyl-l-aspartyl-l-glutamate. The PSMA structure will facilitate development of chemotherapeutics, cancer-imaging agents, and agents for treatment of neurological disorders.

The Kell protein of the common K2 phenotype is a catalytically active metalloprotease, whereas the rare Kell K1 antigen is inactive. Identification of novel substrates for the Kell protein.

The Kell blood group is a highly polymorphic system containing over 20 different antigens borne by the protein Kell, a 93-kDa type II glycoprotein that displays high sequence homology with members of the M13 family of zinc-dependent metalloproteases whose prototypical member is neprilysin. Kell K1 is an antigen expressed in 9% of the Caucasian population, characterized by a point mutation (T193M) of the Kell K2 antigen, and located within a putative N-glycosylation consensus sequence. Recently, a recombinant, non-physiological, soluble form of Kell was shown to cleave Big ET-3 to produce the mature vasoconstrictive peptide. To better characterize the enzymatic activity of the Kell protein and the possible differences introduced by antigenic point mutations affecting post-translational processing, the membrane-bound forms of the Kell K1 and Kell K2 antigens were expressed either in K562 cells, an erythroid cell line, or in HEK293 cells, a non-erythroid system, and their pharmacological profiles and enzymatic specificities toward synthetic and natural peptides were evaluated. Results presented herein reveal that the two antigens possess considerable differences in their enzymatic activities, although not in their trafficking pattern. Indeed, although both antigens are expressed at the cell surface, Kell K1 protein is shown to be inactive, whereas the Kell K2 antigen binds neprilysin inhibitory compounds such as phosphoramidon and thiorphan with high affinity, cleaves the precursors of the endothelin peptides, and inactivates members of the tachykinin family with enzymatic properties resembling those of other members of the M13 family of metalloproteases to which it belongs.

Fluorescence resonance energy transfer reports properties of syntaxin1a interaction with Munc18-1 in vivo.

Syntaxin1A, a neural-specific N-ethylmaleimide-sensitive factor attachment protein receptor protein essential to neurotransmitter release, in isolation forms a closed conformation with an N-terminal alpha-helix bundle folded upon the SNARE motif (H3 domain), thereby limiting interaction of the H3 domain with cognate SNAREs. Munc18-1, a neural-specific member of the Sec1/Munc18 protein family, binds to syntaxin1A, stabilizing this closed conformation. We used fluorescence resonance energy transfer (FRET) to characterize the Munc18-1/syntaxin1A interaction in intact cells. Enhanced cyan fluorescent protein-Munc18-1 and a citrine variant of enhanced yellow fluorescent protein-syntaxin1A, or mutants of these proteins, were expressed as donor and acceptor pairs in human embryonic kidney HEK293-S3 and adrenal chromaffin cells. Apparent FRET efficiency was measured using two independent approaches with complementary results that unambiguously verified FRET and provided a spatial map of FRET efficiency. In addition, enhanced cyan fluorescent protein-Munc18-1 and a citrine variant of enhanced yellow fluorescent protein-syntaxin1A colocalized with a Golgi marker and exhibited FRET at early expression times, whereas a strong plasma membrane colocalization, with similar FRET values, was apparent at later times. Trafficking of syntaxin1A to the plasma membrane was dependent on the presence of Munc18-1. Both syntaxin1A(L165A/E166A), a constitutively open conformation mutant, and syntaxin1A(I233A), an H3 domain point mutant, demonstrated apparent FRET efficiency that was reduced approximately 70% from control. In contrast, the H3 domain mutant syntaxin1A(I209A) had no effect. By using phosphomimetic mutants of Munc18-1, we also established that Ser-313, a Munc18-1 protein kinase C phosphorylation site, and Thr-574, a cyclin-dependent kinase 5 phosphorylation site, regulate Munc18-1/syntaxin1A interaction in HEK293-S3 and chromaffin cells. We conclude that FRET imaging in living cells may allow correlated regulation of Munc18-1/syntaxin1A interactions to Ca(2+)-regulated secretory events.

Prostaglandin A2-mediated stabilization of p21 mRNA through an ERK-dependent pathway requiring the RNA-binding protein HuR.

Treatment with the stress agent prostaglandin A2 (PGA2) induces expression of the cyclin-dependent kinase inhibitor p21. Here, we present evidence that p21 expression increases through PGA2-triggered stabilization of the p21 mRNA and further show that these events require the mitogen-activated protein (MAP) kinase ERK. Binding experiments using either endogenous p21 mRNA or in vitro-labeled p21 transcripts revealed a specific PGA2-dependent association of the p21 mRNA with the RNA-binding protein HuR. Interestingly, although inhibition of the ERK pathway did not prevent the PGA2-triggered increase in cytoplasmic HuR, it did impair the formation of endogenous and in vitro [HuR-p21 mRNA] complexes and further prevented the PGA2-mediated stabilization of the p21 mRNA, suggesting that ERK-mediated events were required for binding HuR to the p21 mRNA and preventing its decay. RNA interference-based knockdown of HuR abundance further served to demonstrate the contribution of HuR-mediated p21 mRNA stabilization toward enhancing p21 expression after PGA2 treatment. Collectively, our results indicate that PGA2 stabilizes the p21 mRNA through an ERK-independent increase in cytoplasmic HuR levels and an ERK-dependent association of HuR with the p21 mRNA.

Complementary DNA cloning and characterization of RANDAM-2, a type I membrane molecule specifically expressed on glutamatergic neuronal cells in the mouse cerebrum.

A membrane-surface glycoprotein, RANDAM-2, is one of the neuronal cell lineage-specific antigens involved in the neuronal differentiation of P19 embryonic carcinoma (EC) cells and the mouse central nervous system (CNS). Complementary DNA cloning of RANDAM-2 indicated that its nucleotide sequence completely matched that of PA2.26 antigen, a sialomucin-like transmembrane glycoprotein previously found on tumorigenic keratinocytes. RANDAM-2 transcripts were detectable from the embryonic stage of 6.5 days, and then the expression continued throughout the remaining embryonic stages and adulthood, with a localization restricted to the CNS. In growth factor-induced neurospheres and adult cerebrum, RANDAM-2-expressing cells coincided well not only with nestin-positive cells but also with glutamate-positive neurons, but not with gamma-aminobutyric acid-positive ones. These results indicate that RANDAM-2 is one of the type I membrane surface antigens constitutively expressed on undifferentiated neuronal cells and the glutamatergic neuronal cells during mouse neurogenesis.

Active amino acids of the Kell blood group protein and model of the ectodomain based on the structure of neutral endopeptidase 24.11.

In addition to its importance in transfusion, Kell protein is a member of the M13 family of zinc endopeptidases and functions as an endothelin-3-converting enzyme. To obtain information on the structure of Kell protein we built a model based on the crystal structure of the ectodomain of neutral endopeptidase 24.11 (NEP). Similar to NEP, the Kell protein has 2 globular domains consisting mostly of alpha-helical segments. The domain situated closest to the membrane contains both the N- and C-terminal sequences and the enzyme-active site. The outer domain contains all of the amino acids whose substitutions lead to different Kell blood group phenotypes. In the model, the zinc peptidase inhibitor, phosphoramidon, was docked in the active site. Site-directed mutagenesis of amino acids in the active site was performed and the enzymatic activities of expressed mutant Kell proteins analyzed and compared with NEP. Our studies indicate that Kell and NEP use the same homologous amino acids in the coordination of zinc and in peptide hydrolysis. However, Kell uses different amino acids than NEP in substrate binding and appears to have more flexibility in the composition of amino acids allowed in the active site.

Mechanism of activation of human peripheral blood NK cells at the single cell level by Echinacea water soluble extracts: recruitment of lymphocyte-target conjugates and killer cells and activation of programming for lysis.

Echinacea purpurea, a plant originally used by native Americans to treat respiratory infections, has also been shown to exert immunomodulatory activities both in vivo and in vitro. However, the mechanism underlying Echinacea-induced immunomodulation remains largely unknown. This study examined in vitro the effects of soluble extracts of E. purpurea on natural killer (NK) cells present in human peripheral blood mononuclear cells (PBMC). Flow cytometric methods were used to examine activation, cytotoxicity, NK-target binding, and killer cell frequency. Treatment of PBMC with Echinacea overnight resulted in the activation of CD69 expression and increase in mean fluorescence intensity in both the CD16+ and CD16+CD56+ NK subsets. However, the frequency of CD16+ cells was decreased as well as the mean fluorescence intensity was down-regulated. NK cytotoxicity was augmented 100% at the concentration of 0.1 microg/ml of Echinacea in a short time (4-h) assay. Examination at the single cell level revealed augmentation of the frequency of CD56+ NK-target conjugates and a plateau was reached after 30-60 min of incubation. Likewise, the frequency of CD56+ killer cells in the conjugates was also significantly increased by Echinacea. There was recruitment of non-conjugated CD56+ cells into CD16+ NK-target conjugates and activation of the NK-target non-killer conjugates into killer cells. These findings demonstrate that Echinacea extracts are potent activators of NK cytotoxicity. Echinacea augments the frequency of NK target conjugates and activates the programming for lysis of NK cells.

The C2A domain of synaptotagmin alters the kinetics of voltage-gated Ca2+ channels Ca(v)1.2 (Lc-type) and Ca(v)2.3 (R-type).

Biochemical and genetic studies implicate synaptotagmin (Syt 1) as a Ca2+ sensor for neuronal and neuroendocrine neurosecretion. Calcium binding to Syt 1 occurs through two cytoplasmic repeats termed the C2A and C2B domains. In addition, the C2A domain of Syt 1 has calcium-independent properties required for neurotransmitter release. For example, mutation of a polylysine motif (residues 189-192) reverses the inhibitory effect of injected recombinant Syt 1 C2A fragment on neurotransmitter release from PC12 cells. Here we examined the requirement of the C2A polylysine motif for Syt 1 interaction with the cardiac Cav1.2 (L-type) and the neuronal Cav2.3 (R-type) voltage-gated Ca2+ channels, two channels required for neurotransmission. We find that the C2A polylysine motif presents a critical interaction surface with Cav1.2 and Cav2.3 since truncated Syt 1 containing a mutated motif (Syt 1*1-264) was ineffective at modifying the channel kinetics. Mutating the polylysine motif also abolished C2A binding to Lc753-893, the cytosolic interacting domain of Syt 1 at Cav1.2 1 subunit. Syt 1 and Syt 1* harboring the mutation at the KKKK motif modified channel activation, while Syt 1* only partially reversed the syntaxin 1A effects on channel activity. This mutation would interfere with the assembly of Syt 1/channel/syntaxin into an exocytotic unit. The functional interaction of the C2A polylysine domain with Cav1.2 and Cav2.3 is consistent with tethering of the secretory vesicle to the Ca2+ channel. It indicates that calcium-independent properties of Syt 1 regulate voltage-gated Ca2+ channels and contribute to the molecular events underlying transmitter release.

Effects of the isolation methodology on protein profiles of blood trypomastigotes of Trypanosoma cruzi.

Blood trypomastigotes of Trypanosoma cruzi were isolated from infected athymic rnu/rnu rats and purified by an improved procedure of DEAE-Sephacel ion-exchange chromatography. Elution into a buffer supplemented with bovine serum albumin avoided column-induced changes on the surface of the parasites. Biotin-labelled bovine serum albumin, fluorescence microscopy, flow cytometry and Western blot analysis revealed a very intense binding of albumin to the parasite. Incubation and washing of cells without protein supplementation did not result in any damage or lysis of parasites but it did cause extensive shedding of cellular and surface proteins into the supernatant which could be prevented by using the protein-supplemented buffer. A decreasing yield of high molecular weight cellular proteins in relation to centrifugal force was a general phenomenon observed in scanning densitometry of SDS gels after isolation in either protein-supplemented buffer or protein-free buffer. The quantity of shed cellular components increased with increasing centrifugal force. In contrast, quantities of high molecular weight, biotin-labelled surface proteins increased with greater centrifugal force, indicating labelling of otherwise inaccessible residues. These data emphasize the importance of protein supplementation of buffers with proteins and of choosing low centrifugation forces (<400 g) during investigations of T. cruzi.

Immunological and biochemical analysis of glycosylated surface antigens and lipophosphoglycan of Tritrichomonas foetus.

Immunoaffinity-purified TF1.17 adhesin antigen was compared biochemically and antigenically to Tritrichomonas foetus (TF) lipophosphoglycan (LPG) and a soluble glycosylated antigen (SGA) released from T. foetus and implicated in pathogenesis and immunity. The monoclonal antibodies (Mabs TF1.15 and TF1.17) specific for a glycosylated TF1.17 antigen were previously shown to prevent adhesion of the T. foetus parasites to bovine vaginal epithelial cells and to mediate killing by bovine complement. SGA was isolated from T. foetus-conditioned buffer and purified by octyl-Sepharose hydrophobic column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of SGA showed a major SGA1 component (approximately 190 kDa) and a minor SGA2 component (50-70 kDa), which migrated close to TF-LPG and TF1.17. The carbohydrate and lipid compositional analyses of affinity-purified TF1.17 and SGA2 by high-performance liquid chromatography (HPLC) and gas-liquid chromatography revealed the presence of monosaccharides and fatty acids as found in TF-LPG. All antigens contained terminal fucose as determined by alpha-fucosidase digestion followed by HPLC. ELISA and western blots were used to further characterize these glycosylated antigens and to analyze their relationships. The Mabs TF1.15 and TF1.17 reacted very strongly to TF-LPG and SGA2. as well as TF1.17 antigen, indicating that these molecules share common epitopes. These Mabs did not react with the SGA1 component either in ELISA and western blot analyses. Also, the monosaccharide composition of SGA1 was very different from the other three antigen, suggesting SGA1 was different from LPG, SGA2 and TF1.17. Although LPG reacted with Mabs to native TF1.17 antigen, LPG did not induce an immune response in cattle with the same route and adjuvant used to produce strong antibody responses to the native antigen. The latter response suggests that the tightly bound peptide present in the immunoaffinity-purified antigen is necessary for induction of a response to (an) epitope(s) in TF-LPG and TF1.17. Furthermore, vaginal fluid from T. foetus-infected heifers and serum from a cow with a T. foetus-associated pyometra recognized both TF1.17 and TF-LPG in western blots. These results suggest that T. foetus LPG and SGA2 are related to TF1.17 antigen, which was previously shown to play an important role in the pathogenesis and host response in bovine trichomoniasis.

Sequence and expression of the SerJ immobilization antigen gene of Tetrahymena thermophila regulated by dominant epistasis.

In ciliates, variable surface protein genes encoding the immobilization antigen (-ag) are expressed under different environmental conditions, including temperature and salt stress. These i-ags are GPI-linked and coat the entire external surface of the cell, including the cilia. In Tetrahymena thermophila-ag in natural isolates is the result of dominant epistasis masking the expression of the H i-ag ordinarily expressed at 20-36 degrees C. This report describes the expression and sequence of the Ser-ag. J is present on the cell surface up to 38 degrees C; above 38 degrees C SerSeranked by an A-rich 5' UTR and a 3' UTR containing putative mRNA destabilization motifs. The encoded J polypeptide consists of 438 amino acids and is rich in alanine, cysteine, serine and threonine. The N- and resemble signal peptide and GPI-anchor addition sites, respectively. The majority of the molecule consists of four imperfect repeats with 10 periodic cysteines per repeat in the pattern CX(6)CX(2)CX(21)CX(4)CX(13-15)CX(2)CX(18)CX(3)CX(11)CX(9-10). Although H i-ags encoded by paralogous SerH genes have 3.5 imperfect repeats with eight periodic cysteines per repeat, J nevertheless resembles H with respect to amino acid composition, codon usage, N- and C-termini, the arrangement of the cysteine periods, and regulation by mRNA stability. However, despite these similarities and epistasis, the evolutionary relationship between SerH and SerJ is unclear.