Cutting edge: CD8+ T cell priming in the absence of NK cells leads to enhanced memory responses

It is uncertain whether NK cells modulate T cell memory differentiation. By using a genetic model that allows the selective depletion of NK cells, we show in this study that NK cells shape CD8(+) T cell fate by killing recently activated CD8(+) T cells in an NKG2D- and perforin-dependent manner. In the absence of NK cells, the differentiation of CD8(+) T cells is strongly biased toward a central memory T cell phenotype. Although, on a per-cell basis, memory CD8(+) T cells generated in the presence or the absence of NK cells have similar functional features and recall capabilities, NK cell deletion resulted in a significantly higher number of memory Ag-specific CD8(+) T cells, leading to more effective control of tumors carrying model Ags. The enhanced memory responses induced by the transient deletion of NK cells may provide a rational basis for the design of new vaccination strategies.     

Genotypic and phenotypic evaluation of Rutilus spp. from Skadar, Ohrid and Prespa Lakes supports revision of endemic as well as taxonomic status of several taxa

One mtDNA gene (cytochrome b), one nuclear DNA fragment, five microsatellites and a suite of morphological characters were evaluated in samples of Rutilus spp. from Skadar, Ohrid and Prespa Lakes. Both genetic and phenotypic data supported two sympatric taxa in Lake Skadar, whereby Prespa and Ohrid Lakes revealed only a single taxon each. One of the taxa from Lake Skadar was similar to samples from Lake Prespa, whereas the second taxon was the most divergent in the data set. The estimated time to the most recent common ancestor of these two sympatric taxa in Lake Skadar was between 125 000 and 500 000 years. The data did not support existing taxonomic schemes for Rutilus in these lakes. This study poses the following working hypothesis: (1) Rutilus prespensis lives both in Lake Prespa and Lake Skadar and therefore is not endemic to Lake Prespa, (2) Rutilus ohridanus lives in Lake Ohrid only and therefore could be considered an endemic if its species status is retained and (3) a third recently described taxon (Rutilus albus) sympatric to R. prespensis lives in Lake Skadar.     

The Negative Effect of Soy Extract on Erythrocyte Membrane Fluidity: An Electron Paramagnetic Resonance Study

A decrease of erythrocyte membrane fluidity can contribute to the pathophysiology of hypertension. Soy products, which are used as alternative therapeutics in some cardiovascular conditions, contain various isoflavones (genistein, daidzein, and their glucosides, genistin and daidzin), which can incorporate cellular membrane and change its fluidity. The aim of this study was to examine the effects of soy extract (which generally corresponds to the soy products of isoflavone composition) on erythrocyte membrane fluidity at graded depths. We used electron paramagnetic resonance spectroscopy and fatty acid spin probes (5-DS and 12-DS), the spectra of which are dependent on membrane fluidity. After being treated with soy extract, erythrocytes showed a significant (P = 0.016) decrease of membrane fluidity near the hydrophilic surface, while there were no significant changes of fluidity in deeper hydrophobic membrane regions. These results suggest that soy products containing high levels of genistein and isoflavone glucosides may not be suitable for use in hypertension because they decrease erythrocyte membrane fluidity.     

Systematic analysis of the amino acid residues of human papillomavirus type 16 E7 conserved region 3 involved in dimerization and transformation

The human papillomavirus (HPV) E7 oncoprotein exists as a dimer and acts by binding to many cellular factors, preventing or retargeting their function and thereby making the infected cell conducive for viral replication. Dimerization of E7 is attributed primarily to the C-terminal domain, referred to as conserved region 3 (CR3). CR3 is highly structured and is necessary for E7's transformation ability. It is also required for binding of numerous E7 cellular targets. To systematically analyze the molecular mechanisms by which HPV16 E7 CR3 contributes to carcinogenesis, we created a comprehensive panel of mutations in residues predicted to be exposed on the surface of CR3. We analyzed our novel collection of mutants, as well as mutants targeting predicted hydrophobic core residues of the dimer, for the ability to dimerize. The same set of mutants was also assessed functionally for transformation capability in a baby rat kidney cell assay in conjugation with activated ras. We show that some mutants of HPV16 E7 CR3 failed to dimerize yet were still able to transform baby rat kidney cells. Our results identify several novel E7 mutants that abrogate transformation and also indicate that E7 does not need to exist as a stable dimer in order to transform cells.     

Insight into the short-finned squid Illex coindetii (Cephalopoda: Ommastrephidae) feeding ecology: is there a link between helminth parasites and food composition?

Squids are especially frequent as paratenic hosts of helminth parasites, particularly to those that have elasmobranchs and mammals as final hosts. Among those parasite species, anisakid nematode larvae and cestode plerocercoids are most effectively transferred through the trophic chain by oegopsid squids. A total of 439 short-finned squids, Illex coindetii (245 males, 190 females and 4 unsexed) were sampled in the central part of the eastern Adriatic Sea in order to assess their helminth component community and parasite dynamics with respect to host sex, maturity, seasonality, and feeding behavior. Two larval helminths were isolated, i.e., larvae of Anisakis pegreffii, characterized by molecular tools at the species level, and plerocercoids of Phyllobothrium sp., with prevalences of 30.5% and 2.3%, respectively. Highly significant seasonal variation in diet consumption, congruent with seasonal variation in anisakid intensity, was observed, underlining the tight role of squid prey in the trophic transmission of parasite. Likewise, the highest helminth prevalence and intensity of infection was recorded in autumn, when the fish prey, mostly Maurolicus muelleri, comprised the greatest proportion of diet. This helped to assign the Adriatic broadtail shortfin squid not as a first, but as a second, paratenic host for the anisakid, unlike as suggested previously. The presence of larval A. pegreffii confirms its previously reported zoogeographical distribution in the Mediterranean and Adriatic Seas. The presence of 2 helminths in I. coindetii describes the feeding patterns of the squid, as well as clearly defined and coevolved predator-prey relationships.     

Unexpected diversity of chlorite dismutases: a catalytically efficient dimeric enzyme from Nitrobacter winogradskyi

Chlorite dismutase (Cld) is a unique heme enzyme catalyzing the conversion of ClO(2)(-) to Cl(-) and O(2). Cld is usually found in perchlorate- or chlorate-reducing bacteria but was also recently identified in a nitrite-oxidizing bacterium of the genus Nitrospira. Here we characterized a novel Cld-like protein from the chemolithoautotrophic nitrite oxidizer Nitrobacter winogradskyi which is significantly smaller than all previously known chlorite dismutases. Its three-dimensional (3D) crystal structure revealed a dimer of two identical subunits, which sharply contrasts with the penta- or hexameric structures of other chlorite dismutases. Despite a truncated N-terminal domain in each subunit, this novel enzyme turned out to be a highly efficient chlorite dismutase (K(m) = 90 μM; k(cat) = 190 s(-1); k(cat)/K(m) = 2.1 × 10(6) M(-1) s(-1)), demonstrating a greater structural and phylogenetic diversity of these enzymes than was previously known. Based on comparative analyses of Cld sequences and 3D structures, signature amino acid residues that can be employed to assess whether uncharacterized Cld-like proteins may have a high chlorite-dismutating activity were identified. Interestingly, proteins that contain all these signatures and are phylogenetically closely related to the novel-type Cld of N. winogradskyi exist in a large number of other microbes, including other nitrite oxidizers.     

Intragene higher order repeats in neuroblastoma breakpoint family genes distinguish humans from chimpanzees

Much attention has been devoted to identifying genomic patterns underlying the evolution of the human brain and its emergent advanced cognitive capabilities, which lie at the heart of differences distinguishing humans from chimpanzees, our closest living relatives. Here, we identify two particular intragene repeat structures of noncoding human DNA, spanning as much as a hundred kilobases, that are present in human genome but are absent from the chimpanzee genome and other nonhuman primates. Using our novel computational method Global Repeat Map, we examine tandem repeat structure in human and chimpanzee chromosome 1. In human chromosome 1, we find three higher order repeats (HORs), two of them novel, not reported previously, whereas in chimpanzee chromosome 1, we find only one HOR, a 2mer alphoid HOR instead of human alphoid 11mer HOR. In human chromosome 1, we identify an HOR based on 39-bp primary repeat unit, with secondary, tertiary, and quartic repeat units, fully embedded in human hornerin gene, related to regenerating and psoriatric skin. Such an HOR is not found in chimpanzee chromosome 1. We find a remarkable human 3mer HOR organization based on the ~1.6-kb primary repeat unit, fully embedded within the neuroblastoma breakpoint family genes, which is related to the function of the human brain. Such HORs are not present in chimpanzees. In general, we find that human-chimpanzee differences are much larger for tandem repeats, in particularly for HORs, than for gene sequences. This may be of great significance in light of recent studies that are beginning to reveal the large-scale regulatory architecture of the human genome, in particular the role of noncoding sequences. We hypothesize about the possible importance of human accelerated HOR patterns as components in the gene expression multilayered regulatory network.