Adenosinergic regulation of the expansion and immunosuppressive activity of CD11b+Gr1+ cells

Extracellular adenosine and purine nucleotides are elevated in many pathological situations associated with the expansion of CD11b(+)Gr1(+) myeloid-derived suppressor cells (MDSCs). Therefore, we tested whether adenosinergic pathways play a role in MDSC expansion and functions. We found that A(2B) adenosine receptors on hematopoietic cells play an important role in accumulation of intratumoral CD11b(+)Gr1(high) cells in a mouse Lewis lung carcinoma model in vivo and demonstrated that these receptors promote preferential expansion of the granulocytic CD11b(+)Gr1(high) subset of MDSCs in vitro. Flow cytometry analysis of MDSCs generated from mouse hematopoietic progenitor cells revealed that the CD11b(+)Gr-1(high) subset had the highest levels of CD73 (ecto-5'-nucleotidase) expression (Δmean fluorescence intensity [MFI] of 118.5 ± 16.8), followed by CD11b(+)Gr-1(int) (ΔMFI of 57.9 ± 6.8) and CD11b(+)Gr-1(-/low) (ΔMFI of 12.4 ± 1.0) subsets. Even lower levels of CD73 expression were found on Lewis lung carcinoma tumor cells (ΔMFI of 3.2 ± 0.2). The high levels of CD73 expression in granulocytic CD11b(+)Gr-1(high) cells correlated with high levels of ecto-5'-nucleotidase enzymatic activity. We further demonstrated that the ability of granulocytic MDSCs to suppress CD3/CD28-induced T cell proliferation was significantly facilitated in the presence of the ecto-5'-nucleotidase substrate 5'-AMP. We propose that generation of adenosine by CD73 expressed at high levels on granulocytic MDSCs may promote their expansion and facilitate their immunosuppressive activity.     

Archaeal translation initiation factor aIF2 can substitute for eukaryotic eIF2 in ribosomal scanning during mammalian 48S complex formation

Heterotrimeric translation initiation factor (IF) a/eIF2 (archaeal/eukaryotic IF 2) is present in both Eukarya and Archaea. Despite strong structural similarity between a/eIF2 orthologs from the two domains of life, their functional relationship is obscure. Here, we show that aIF2 from Sulfolobus solfataricus can substitute for its mammalian counterpart in the reconstitution of eukaryotic 48S initiation complexes from purified components. aIF2 is able to correctly place the initiator Met-tRNA_i into the P-site of the 40S ribosomal subunit and accompany the entire set of eukaryotic translation IFs in the process of cap-dependent scanning and AUG codon selection. However, it seems to be unable to participate in the following step of ribosomal subunit joining. In accordance with this, aIF2 inhibits rather than stimulates protein synthesis in mammalian cell-free system. The ability of recombinant aIF2 protein to direct ribosomal scanning suggests that some archaeal mRNAs may utilize this mechanism during translation initiation.     

First record of the subfamily Dirrhopinae (Hymenoptera: Braconidae) from the Australian region, with a discussion of relationships and biology

Abstract The subfamily Dirrhopinae (Hymenoptera: Braconidae) is recorded for the first time from the Australian region on the basis of Dirrhope minor Belokobylskij collected at light from several sites in northern Queensland. The species is redescribed and a discussion of relationships, distribution and biology of the subfamily is presented.     

A new species of the feather mite genus Titanolichus Gaud & Atyeo, 1996 (Acari: Astigmata: Pterolichidae) from the endangered orange-bellied parrot Neophema chrysogaster (Aves: Psittaciformes) from Australia

Abstract  Titanolichus seemani sp. n., a new species of the genus Titanolichus Gaud & Atyeo, 1996, is described from a museum skin of the endangered orange-bellied parrot Neophema chrysogaster (Latham) (Aves: Psittaciformes) from Australia. We also redescribe the type species Titanolichus chiragricus (Mégnin & Trouessart) from the ground parrot Pezoporus wallicus (Kerr), provide a key for all known species of Titanolichus and point out some problems in the systematics of this genus.     

Switching the substrate specificity of the two-component NS2B-NS3 flavivirus proteinase by structure-based mutagenesis

The flavivirus NS2B-NS3(pro)teinase is an essential element in the proteolytic processing of the viral precursor polyprotein and therefore a potential drug target. Recently, crystal structures and substrate preferences of NS2B-NS3pro from Dengue and West Nile viruses (DV and WNV) were determined. We established that the presence of Gly-Gly at the P1'-P2' positions is optimal for cleavage by WNV NS3pro, whereas DV NS3pro tolerates well the presence of bulky residues at either P1' or P2'. Structure-based modeling suggests that Arg(76) and Pro(131)-Thr(132) limit the P1'-P2' subsites and restrict the cleavage preferences of the WNV enzyme. In turn, Leu(76) and Lys(131)-Pro(132) widen the specificity of DV NS3pro. Guided by these structural models, we expressed and purified mutant WNV NS2B-NS3pro and evaluated cleavage preferences by using positional scanning of the substrate peptides in which the P4-P1 and the P3'-P4' positions were fixed and the P1' and P2' positions were each randomized. We established that WNV R76L and P131K-T132P mutants acquired DV-like cleavage preferences, whereas T52V had no significant effect. Our work is the first instance of engineering a viral proteinase with switched cleavage preferences and should provide valuable data for the design of optimized substrates and substrate-based selective inhibitors of flaviviral proteinases.     

Human immunodeficiency virus type 1 protease cleaves procaspase 8 in vivo

Human immunodeficiency virus type 1 (HIV-1) infection causes apoptosis of infected CD4 T cells as well as uninfected (bystander) CD4 and CD8 T cells. It remains unknown what signals cause infected cells to die. We demonstrate that HIV-1 protease specifically cleaves procaspase 8 to create a novel fragment termed casp8p41, which independently induces apoptosis. casp8p41 is specific to HIV-1 protease-induced death but not other caspase 8-dependent death stimuli. In HIV-1-infected patients, casp8p41 is detected only in CD4(+) T cells, predominantly in the CD27(+) memory subset, its presence increases with increasing viral load, and it colocalizes with both infected and apoptotic cells. These data indicate that casp8p41 independently induces apoptosis and is a specific product of HIV-1 protease which may contribute to death of HIV-1-infected cells.