Protein energy malnutrition impairs homeostatic proliferation of memory CD8 T cells

Nutrition is a critical but poorly understood determinant of immunity. There is abundant epidemiological evidence linking protein malnutrition to impaired vaccine efficacy and increased susceptibility to infections; yet, the role of dietary protein in immune memory homeostasis remains poorly understood. In this study, we show that protein-energy malnutrition induced in mice by low-protein (LP) feeding has a detrimental impact on CD8 memory. Relative to adequate protein (AP)-fed controls, LP feeding in lymphocytic choriomeningitis virus (LCMV)-immune mice resulted in a 2-fold decrease in LCMV-specific CD8 memory T cells. Adoptive transfer of memory cells, labeled with a division tracking dye, from AP mice into naive LP or AP mice demonstrated that protein-energy malnutrition caused profound defects in homeostatic proliferation. Remarkably, this defect occurred despite the lymphopenic environment in LP hosts. Whereas Ag-specific memory cells in LP and AP hosts were phenotypically similar, memory cells in LP hosts were markedly less responsive to polyinosinic-polycytidylic acid-induced acute proliferative signals. Furthermore, upon recall, memory cells in LP hosts displayed reduced proliferation and protection from challenge with LCMV-clone 13, resulting in impaired viral clearance in the liver. The findings show a metabolic requirement of dietary protein in sustaining functional CD8 memory and suggest that interventions to optimize dietary protein intake may improve vaccine efficacy in malnourished individuals.     

Evidence that the amino acid residue Ile121 is involved in arginine kinase activity and structural stability

Arginine kinase (AK) catalyzes the reversible phosphorylation of arginine by ATP, yielding the phosphoarginine. Domain-domain interactions may be very important to the structure and functions of many multidomain proteins. However, little is known about the role of amino acid residues located in the linker between the N- and C-terminal domains in the structural stability and functions of multidomain proteins. In this research, A series mutation of conserved residue Ile121 located in the linker were mutated to explore its roles in the activity and structural stability of AK. The mutations I121D and I121K led to pronounced loss of activity and structural stability. Furthermore, these mutations also led to serious aggregation during heat-and GdnHCl-induced denaturation and refolding from the GdnHCl-denatured state. More importantly, all the mutantions except I121L could not successfully recover their activities by dilution-initiated refolding, and showed significant decreased rate constant during AK refolding. While the mutation I121L almost had no effect on AK activity and structural stability. These results suggested that mutations of the residue I121 in the linker might affect the correct positioning of the domains and thus disrupt the efficient recognition and interactions between the N- and C-terminal domains.     

Identification of a broad-spectrum arenavirus entry inhibitor

Several arenaviruses, including Lassa virus (LASV), are causative agents of hemorrhagic fever, for which effective therapeutic options are lacking. The LASV envelope glycoprotein (GP) gene was used to generate lentiviral pseudotypes to identify small-molecule inhibitors of viral entry. A benzimidazole derivative with potent antiviral activity was identified from a high-throughput screen utilizing this strategy. Subsequent lead optimization for antiviral activity identified a modified structure, ST-193, with a 50% inhibitory concentration (IC(50)) of 1.6 nM against LASV pseudotypes. ST-193 inhibited pseudotypes generated with other arenavirus envelopes as well, including the remaining four commonly associated with hemorrhagic fever (IC(50)s for Junín, Machupo, Guanarito, and Sabiá were in the 0.2 to 12 nM range) but exhibited no antiviral activity against pseudotypes incorporating either the GP from the LASV-related arenavirus lymphocytic choriomeningitis virus (LCMV) or the unrelated G protein from vesicular stomatitis virus, at concentrations of up to 10 microM. Determinants of ST-193 sensitivity were mapped through a combination of LASV-LCMV domain-swapping experiments, genetic selection of viral variants, and site-directed mutagenesis. Taken together, these studies demonstrate that sensitivity to ST-193 is dictated by a segment of about 30 amino acids within the GP2 subunit. This region includes the carboxy-terminal region of the ectodomain and the predicted transmembrane domain of the envelope protein, revealing a novel antiviral target within the arenavirus envelope GP.     

Synthesis and evaluation of bifunctional nitrocatechol inhibitors of pig liver catechol-O-methyltransferase

Bifunctional compounds were tested in vitro as potential inhibitors of pig liver catechol-O-methyltransferase (COMT) with respect to the catechol substrate 4-[(3,4-dihydroxyphenyl)azo]benzenesulfonate. The bifunctional compounds were a composite of either two nitrocatechols or one nitrocatechol and one phenol, linked by amide bonds to a spacer unit comprising two to five methylene groups. The unsymmetrical compounds N-[2-(4-hydroxybenzoylamine)ethyl]-3,4-dihydroxy-5-nitrobenzamide], N-[3-(4-hydroxybenzoyl-amine)propyl]-3,4-dihydroxy-5-nitrobenzamide] and N-[5-(4-hydroxybenzoylamine)pentyl]-3,4-dihydroxy-5-nitrobenzamide] demonstrated strong inhibitory action against COMT with K(i) values in the 100 nM range. In comparison, the monofunctional nitrocatechol analogues of these compounds had K(i) values that were significantly higher.     

Scintigraphic Detection of Dual Ectopic Thyroid Tissue: Experience of a Chinese Tertiary Hospital

Purpose

To assess scintigraphic pattern, clinical indication and relevance of dual ectopic thyroid tissue (ETT). Literature is reviewed for such cases.

Methods

In this 5-year retrospective study, we reviewed all thyroid scintigraphies in our data base. Patients diagnosed with suspected ETT were identified. Literature is reviewed. Statistics were done by one-way analysis of variance and least significant difference test.

Results

From 11905 thyroid scintigraphies during the 5-year period, we retrieved 121 patients eligible for analysis. The top two indications were assessing a palpable front neck mass to determine whether it was an ETT, and primary hypothyroidism. Patients were divided into 3 groups. Group 1 with single ETT (83 cases); group 2 with dual ETT (6 cases) and group 3 with athyroid (32 cases). Age and thyroid hormones were highest in group 2, and lowest in group 3. Thyrotropin was highest in group 3, and lowest in group 2. Thyroxine was given to hypothyroid patients, while no surgery was performed. There were 42 published cases with dual ETT, most of whom were under 30 years old. 38.10% of them were euthyroid, 33.33% hypothyroid, and 21.43% subclinical hypothyroid. Most frequent ectopic positions included lingual (33.73%), sublingual (27.71%) and subhyoid (22.89%).

Conclusions

In our cohort, incidence of dual ETT was 0.05% if the denominator was total number of thyroid scintigraphies. The incidence was 4.96% if the denominator was the number of patients with suspected ETT. Important clinical indication is a front neck palpable mass suggestive of an ETT. Important clinical relevance of recognizing the dual ETT pattern is to avoid inappropriate surgery. After reviewing all published cases, we find dual ETT is often seen in young patients. Most of such patients are euthyroid or mildly hypothyroid. Thyroid ectopia often resides in lingual, sublingual and subhyoid areas.     

A naturally occurring nonapeptide functionally compensates for the CP1 domain of leucyl-tRNA synthetase to modulate aminoacylation activity

aaRSs (aminoacyl-tRNA synthetases) establish the rules of the genetic code by catalysing the formation of aminoacyl-tRNA. The quality control for aminoacylation is achieved by editing activity, which is usually carried out by a discrete editing domain. For LeuRS (leucyl-tRNA synthetase), the CP1 (connective peptide 1) domain is the editing domain responsible for hydrolysing mischarged tRNA. The CP1 domain is universally present in LeuRSs, except MmLeuRS (Mycoplasma mobile LeuRS). The substitute of CP1 in MmLeuRS is a nonapeptide (MmLinker). In the present study, we show that the MmLinker, which is critical for the aminoacylation activity of MmLeuRS, could confer remarkable tRNA-charging activity on the inactive CP1-deleted LeuRS from Escherichia coli (EcLeuRS) and Aquifex aeolicus (AaLeuRS). Furthermore, CP1 from EcLeuRS could functionally compensate for the MmLinker and endow MmLeuRS with post-transfer editing capability. These investigations provide a mechanistic framework for the modular construction of aaRSs and their co-ordination to achieve catalytic efficiency and fidelity. These results also show that the pre-transfer editing function of LeuRS originates from its conserved synthetic domain and shed light on future study of the mechanism.     

Synthesis and evaluation of alkenyl indazoles as selective Aurora kinase inhibitors

A series of alkenyl indazoles were synthesized and evaluated in Aurora kinase enzyme assays. Several promising leads were optimized for selectivity towards Aurora B. Excellent binding affinity and good selectivity were achieved with optimized compounds in isolated Aurora subfamily assays.