HIV-1 Virus Interactions With Host Proteins: Interaction of the N-terminal Domain of the HIV-1 Capsid Protein With Human Calmodulin.

The human immunodeficiency virus (HIV-1 virus) exploits several host factors for assembly, infection, and replication within the infected cells. In this work, we describe the evidence for an interaction of the N-terminal domain of the HIV-1 capsid protein with human calmodulin. The precise role of this interaction within the life cycle of the HIV-1 virus is yet to be defined. Potential roles for this interaction in the viral capsid uncoating are discussed.

In Situ Activation of Pituitary-Infiltrating T Lymphocytes in Autoimmune Hypophysitis.

Autoimmune hypophysitis (AH) is a chronic inflammatory disease characterized by infiltration of T and B lymphocytes in the pituitary gland. The mechanisms through which infiltrating lymphocytes cause disease remain unknown. Using a mouse model of AH we assessed whether T lymphocytes undergo activation in the pituitary gland. Infiltrating T cells co-localized with dendritic cells in the pituitary and produced increased levels of interferon-γ and interleukin-17 upon stimulation in vitro. Assessing proliferation of CD3- and B220-postive lymphocytes by double immunohistochemistry (PCNA-staining) and flow cytometry (BrdU incorporation) revealed that a discrete proportion of infiltrating T cells and B cells underwent proliferation within the pituitary parenchyma. This proliferation persisted into the late disease stage (day 56 post-immunization), indicating the presence of a continuous generation of autoreactive T and B cells within the pituitary gland. T cell proliferation in the pituitary was confirmed in patients affected by autoimmune hypophysitis. In conclusion, we show that pituitary-infiltrating lymphocytes proliferate in situ during AH, providing a previously unknown pathogenic mechanism and new avenues for treatment.

Identification of initial leads directed at the calmodulin-binding region on the Src-SH2 domain that exhibit anti-proliferation activity against pancreatic cancer.

Cellular calmodulin binds to the SH2 domain of Src kinase, and upon Fas activation it recruits Src into the death-inducing signaling complex. This results in Src-ERK activation of cell survival pathway through which pancreatic cancer cells survive and proliferate. We had proposed that the inhibition of the interaction of calmodulin with Src-SH2 domain is an attractive strategy to inhibit the proliferation of pancreatic cancer. Thus we have performed screening of compound libraries by a combination of methods and identified some compounds (initial leads) that target the calmodulin-binding region on the SH2 domain and inhibit the proliferation of pancreatic cancer cells in in vitro assays. Most of these compounds also exhibited varying degrees of cytotoxicity when tested against immortalized breast epithelial cell line (MCF10A). These initial leads are likely candidates for development in targeted delivery of compounds to cancer cells without affecting normal cells.

1H, 15N, and 13C resonance assignments for a monomeric mutant of the HIV-1 capsid protein.

The mature fullerene cone-shaped capsid of the human immunodeficiency virus 1 is composed of about 1,500 copies of the capsid protein (CA). The CA is 231 residues long, and consists of two distinct structural domains, the N-terminal domain and the C-terminal domain (CTD), joined by a flexible linker. The wild type CA exhibits monomer-dimer equilibrium in solution through the CTD-CTD dimerization. This CTD-CTD interaction, together with other intermolecular interdomain interactions, plays significant roles during the assembly of the mature capsid. In addition, CA-CA interactions also play a role in the assembly of the immature virion. The CA also interacts with some host cell proteins within the viral replication cycle. Thus, the capsid protein has been of significant interest as a target for designing inhibitors of assembly of immature virions and mature capsids and inhibitors of its interactions with host cell proteins. However, the equilibrium exhibited by the wild-type CA protein between the monomeric and dimeric states, along with the inherent flexibility from the interdomain linker, have hindered attempts at structural determination by solution NMR and X-ray crystallography methods. In this study, we have utilized a CA protein with W184A and M185A mutations that abolish the dimerization of CA protein as well as its infectivity, but preserve most of the remaining properties of the wild type CA. We have determined the detailed solution structure of the monomeric W184A/M185A-CA protein using 3D-NMR spectroscopy. Here, we present the detailed sequence-specific NMR assignments for this protein.

Structure of a monomeric mutant of the HIV-1 capsid protein.

The capsid protein (CA) of HIV-1 plays a significant role in the assembly of the immature virion and is the critical building block of its mature capsid. Thus, there has been significant interest in the CA protein as a target in the design of inhibitors of early and late stage events in the HIV-1 replication cycle. However, because of its inherent flexibility from the interdomain linker and the monomer-dimer equilibrium in solution, the HIV-1 wild-type CA monomer has defied structural determinations by X-ray crystallography and nuclear magnetic resonance spectroscopy. Here we report the detailed solution structure of full-length HIV-1 CA using a monomeric mutant that, though noninfective, preserves many of the critical properties of the wild-type protein. The structure shows independently folded N-terminal (NTD) and C-terminal domains (CTD) joined by a flexible linker. The CTD shows some differences from that of the dimeric wild-type CTD structures. This study provides insights into the molecular mechanism of the wild-type CA dimerization critical for capsid assembly. The monomeric mutant allows investigation of interactions of CA with human cellular proteins exploited by HIV-1, directly in solution without the complications associated with the monomer-dimer equilibrium of the wild-type protein. This structure also permits the design of inhibitors directed at a novel target, viz., interdomain flexibility, as well as inhibitors that target multiple interdomain interactions critical for assembly and interactions of CA with host cellular proteins that play significant roles within the replication cycle of HIV-1.

Expression of truncated tobacco osmotin in Escherichia coli: purification and antifungal activity.

PURPOSE OF WORK: Tobacco osmotin is a functional homolog of mammalian adiponectin, and has antifungal activity. This work was undertaken to produce recombinant osmotin that has previously been unsuccessful because of its toxicity. Expression of recombinant tobacco osmotin (rOSM) in Escherichia coli inclusion bodies has been achieved. The optimal pH for rOSM expression in ZYM 505 medium is 7.0 at OD(650) of 1.5 of culture growth. The rOSM from the inclusion body was extracted with 8 M urea, and purified using CM-cellulose and cobalt-agarose bead affinity chromatography to a high purity. Approximately 80% of the rOSM remained bound to CM-cellulose and Cobalt-agarose beads after initial elution. The yield of purified rOSM was between 40 and 50 mg from 2 l of culture. Repeated elution of protein from CM-cellulose and Co-agarose increased the yield of rOSM to 200 mg from 2 l culture. The purified rOSM showed variable antifungal activities against two pathogenic yeast strains; Cryptococcus neoformans, Candida albicans, and non-pathogenic strains; Saccharomyces cerevisiae and Pichia methanolica.

Autoimmune hypophysitis of SJL mice: clinical insights from a new animal model.

Autoimmune hypophysitis (AH) is a rare but increasingly recognized disease of the pituitary gland. Its autoantigens are unknown, and the management is difficult because it is often misdiagnosed as a nonsecreting adenoma. By immunizing female SJL/J mice with mouse pituitary extracts, we established a new mouse model of experimental AH. Immunized mice developed severe lymphocytic infiltration in the anterior pituitary that closely mimicked the human pathology. In the early phase of experimental AH, the pituitary enlarged, consistent with the compression symptoms reported by hypophysitis patients at presentation. In the florid phase, adrenal insufficiency and pituitary antibodies developed, in strong correlation with the pituitary pathology. In the late phase, hypothyroidism ensued, and the pituitary gland became atrophic. Using immune sera as probes in a two-dimensional immunoblotting screen followed by mass spectrometry, we identified several proteins that could function as pituitary autoantigens. These findings provide new insights into the pathogenesis of AH, and establish a platform for developing novel diagnostic biomarkers and therapeutics.

Multidrug-resistant Klebsiella pneumoniae isolated from farm environments and retail products in Oklahoma.

Multidrug-resistant enteric bacteria were isolated from turkey, cattle, and chicken farms and retail meat products in Oklahoma. Among the isolated species, multidrug-resistant Klebsiella pneumoniae was prevalently isolated from most of the collected samples. Therefore, a total of 132 isolates of K. pneumoniae were characterized to understand their potential roles in the dissemination of antibiotic-resistance genes in the food chains. Multidrug-resistant K. pneumoniae was most frequently recovered from a turkey farm and ground turkey products among the tested samples. All isolates were resistant to ampicillin, tetracycline, streptomycin, gentamycin, and kanamycin. Class 1 integrons located in plasmids were identified as a common carrier of the aadA1 gene, encoding resistance to streptomycin and spectinomycin. Production of beta-lactamase in the K. pneumoniae isolates played a major role in the resistance to beta-lactam agents. Most isolates (96%) possessed bla(SHV1). Five strains were able to express both SHV-11 (pI 6.2) and TEM-1 (pI 5.2) beta-lactamase. Transfer of these antibiotic-resistance genes to Escherichia coli was demonstrated by transconjugation. The bacterial genomic DNA restriction patterns by pulsed-field gel electrophoresis showed that the same clones of multidrug-resistant K. pneumoniae remained in feathers, feed, feces, and drinking water in turkey environments, indicating the possible dissemination of antibiotic-resistance genes in the ecosystem and cross-contamination of antibiotic-resistant bacteria during processing and distribution of products.