Beta(1)-selective agonist (-)-1-(3,4-dimethoxyphenetylamino)-3-(3,4-dihydroxy)-2-propanol [(-)-RO363] differentially interacts with key amino acids responsible for beta(1)-selective binding in resting and active states.

(-)-1-(3,4-Dimethoxyphenetylamino)-3-(3,4-dihydroxy)-2-propanol [(-)-RO363] is a highly selective beta(1)-adrenergic receptor (beta(1)AR) agonist. To study the binding site of beta(1)-selective agonist, chimeric beta(1)/beta(2)ARs and Ala-substituted beta(1)ARs were constructed. Several key residues of beta(1)AR [Leu(110) and Thr(117) in transmembrane domain (TMD) 2], and Phe(359) in TMD 7] were found to be responsible for beta(1)-selective binding of (-)-RO363, as determined by competitive binding. Based on these results, we built a three-dimensional model of the binding domain for (-)-RO363. The model indicated that TMD 2 and TMD 7 of beta(1)AR form a binding pocket; the methoxyphenyl group of N-substituent of (-)-RO363 seems to locate within the cavity surrounded by Leu(110), Thr(117), and Phe(359). The amino acids Leu(110) and Phe(359) interact with the phenyl ring of (-)-RO363, whereas Thr(117) forms hydrogen bond with the methoxy group of (-)-RO363. To examine the interaction of these residues with beta(1)AR in an active state, each of the amino acids was changed to Ala in a constitutively active (CA)-beta(1)AR mutant. The degree of decrease in the affinity of CA-beta(1)AR for (-)-RO363 was essentially the same as that of wild-type beta(1)AR when mutated at Leu(110) and Thr(117). However, the affinity was decreased in Ala-substituted mutant of Phe(359) compared with that of wild-type beta(1)AR. These results indicated that Leu(110) and Thr(117) are necessary for the initial binding of (-)-RO363 with beta(1)-selectivity, and interaction of Phe(359) with the N-substituent of (-)-RO363 in an active state is stronger than in the resting state.

SV40-induced expression of calretinin protects mesothelial cells from asbestos cytotoxicity and may be a key factor contributing to mesothelioma pathogenesis.

The calcium-binding protein calretinin has emerged as a useful marker for the identification of mesotheliomas of the epithelioid and mixed types, but its putative role in tumor development has not been addressed previously. Although exposure to asbestos fibers is considered the main cause of mesothelioma, undoubtedly, not all mesothelioma patients have a history of asbestos exposure. The question as to whether the SV40 virus is involved as a possible co-factor is still highly debated. Here we show that increased expression of SV40 early gene products in the mesothelial cell line MeT-5A induces the expression of calretinin and that elevated calretinin levels strongly correlate with increased resistance to asbestos cytotoxicity. Calretinin alone mediates a significant part of this protective effect because cells stably transfected with calretinin cDNA were clearly more resistant to the toxic effects of crocidolite than mock-transfected control cells. Down-regulation of calretinin by antisense methods restored the sensitivity to asbestos toxicity to a large degree. The protective effect observed in clones with higher calretinin expression levels could be eliminated by phosphatidylinositol 3-kinase (PI3K) inhibitors, implying an important role for the PI3K/AKT signaling (survival) pathway in mediating the protective effect. Up-regulation of calretinin, resulting from either asbestos exposure or SV40 oncoproteins, may be a common denominator that leads to increased resistance to asbestos cytotoxicity and thereby contributes to mesothelioma carcinogenesis.

Interhuman transmission as a potential key parameter for geographical variation in the prevalence of Pneumocystis jirovecii dihydropteroate synthase mutations.

BACKGROUND: Pneumocystis jirovecii dihydropteroate synthase (DHPS) mutations are associated with failure of prophylaxis with sulfa drugs. This retrospective study sought to better understand the geographical variation in the prevalence of these mutations. METHODS: DHPS polymorphisms in 394 clinical specimens from immunosuppressed patients who received a diagnosis of P. jirovecii pneumonia and who were hospitalized in 3 European cities were examined using polymerase chain reaction (PCR) single-strand conformation polymorphism. Demographic and clinical characteristics were obtained from patients' medical charts. RESULTS: Of the 394 patients, 79 (20%) were infected with a P. jirovecii strain harboring one or both of the previously reported DHPS mutations. The prevalence of DHPS mutations was significantly higher in Lyon than in Switzerland (33.0% vs 7.5%; P < .001). The proportion of patients with no evidence of sulfa exposure who harbored a mutant P. jirovecii DHPS genotype was significantly higher in Lyon than in Switzerland (29.7% vs 3.0%; P < .001). During the study period in Lyon, in contrast to the Swiss hospitals, measures to prevent dissemination of P. jirovecii from patients with P. jirovecii pneumonia were generally not implemented, and most patients received suboptimal prophylaxis, the failure of which was strictly associated with mutated P. jirovecii. Thus, nosocomial interhuman transmission of mutated strains directly or indirectly from other individuals in whom selection of mutants occurred may explain the high proportion of mutations without sulfa exposure in Lyon. CONCLUSIONS: Interhuman transmission of P. jirovecii, rather than selection pressure by sulfa prophylaxis, may play a predominant role in the geographical variation in the prevalence in the P. jirovecii DHPS mutations.

The proteolytic activity of the paracaspase MALT1 is key in T cell activation

The paracaspase MALT1 is pivotal in antigen receptor-mediated lymphocyte activation and lymphomagenesis. MALT1 contains a caspase-like domain, but it is unknown whether this domain is proteolytically active. Here we report that MALT1 had arginine-directed proteolytic activity that was activated after T cell stimulation, and we identify the signaling protein Bcl-10 as a MALT1 substrate. Processing of Bcl-10 after Arg228 was required for T cell receptor-induced cell adhesion to fibronectin. In contrast, MALT1 activity but not Bcl-10 cleavage was essential for optimal activation of transcription factor NF-kappaB and production of interleukin 2. Thus, the proteolytic activity of MALT1 is central to T cell activation, which suggests a possible target for the development of immunomodulatory or anticancer drugs

Identification of a key lysine residue in heat shock protein 90 required for azole and echinocandin resistance in Aspergillus fumigatus.

Heat shock protein 90 (Hsp90) is an essential chaperone involved in the fungal stress response that can be harnessed as a novel antifungal target for the treatment of invasive aspergillosis. We previously showed that genetic repression of Hsp90 reduced Aspergillus fumigatus virulence and potentiated the effect of the echinocandin caspofungin. In this study, we sought to identify sites of posttranslational modifications (phosphorylation or acetylation) that are important for Hsp90 function in A. fumigatus. Phosphopeptide enrichment and tandem mass spectrometry revealed phosphorylation of three residues in Hsp90 (S49, S288, and T681), but their mutation did not compromise Hsp90 function. Acetylation of lysine residues of Hsp90 was recovered after treatment with deacetylase inhibitors, and acetylation-mimetic mutations (K27A and K271A) resulted in reduced virulence in a murine model of invasive aspergillosis, supporting their role in Hsp90 function. A single deletion of lysine K27 or an acetylation-mimetic mutation (K27A) resulted in increased susceptibility to voriconazole and caspofungin. This effect was attenuated following a deacetylation-mimetic mutation (K27R), suggesting that this site is crucial and should be deacetylated for proper Hsp90 function in antifungal resistance pathways. In contrast to previous reports in Candida albicans, the lysine deacetylase inhibitor trichostatin A (TSA) was active alone against A. fumigatus and potentiated the effect of caspofungin against both the wild type and an echinocandin-resistant strain. Our results indicate that the Hsp90 K27 residue is required for azole and echinocandin resistance in A. fumigatus and that deacetylase inhibition may represent an adjunctive anti-Aspergillus strategy.

Tracking individuals shows spatial fidelity is a key regulator of ant social organization.

Ants live in organized societies with a marked division of labor among workers, but little is known about how this division of labor is generated. We used a tracking system to continuously monitor individually tagged workers in six colonies of the ant Camponotus fellah over 41 days. Network analyses of more than 9 million interactions revealed three distinct groups that differ in behavioral repertoires. Each group represents a functional behavioral unit with workers moving from one group to the next as they age. The rate of interactions was much higher within groups than between groups. The precise information on spatial and temporal distribution of all individuals allowed us to calculate the expected rates of within- and between-group interactions. These values suggest that the network of interaction within colonies is primarily mediated by age-induced changes in the spatial location of workers.

Voyages et VIH: les points-clés [Key aspects regarding HIV and travel].

The risk of contracting a sexually transmitted infection while traveling abroad is increased in certain populations. Pre-travel consultation should include the education of travelers on the prevalence of HIV in the countries visited and on appropriate prevention measures. In patients infected with HIV (PHIV), combined antiretroviral therapy (cART) improves immunity, enabling them to travel with less risk for their health. Pre-travel consultation of PVIH has the following objectives: to determine immune status, to update immunization and to decide on anti-malaria drug prophylaxis, taking into account potential drug interactions with antiretroviral therapy. Vaccine response and duration of protection is shorter-lived in PVIH, especially if the CD4 count is below 200 cells/mm3 and the HIV viral load is detectable. Therefore cART is a cornerstone for disease prevention among patients infected with HIV who travel.

The genome of the leaf-cutting ant Acromyrmex echinatior suggests key adaptations to advanced social life and fungus farming.

We present a high-quality (>100× depth) Illumina genome sequence of the leaf-cutting ant Acromyrmex echinatior, a model species for symbiosis and reproductive conflict studies. We compare this genome with three previously sequenced genomes of ants from different subfamilies and focus our analyses on aspects of the genome likely to be associated with known evolutionary changes. The first is the specialized fungal diet of A. echinatior, where we find gene loss in the ant's arginine synthesis pathway, loss of detoxification genes, and expansion of a group of peptidase proteins. One of these is a unique ant-derived contribution to the fecal fluid, which otherwise consists of "garden manuring" fungal enzymes that are unaffected by ant digestion. The second is multiple mating of queens and ejaculate competition, which may be associated with a greatly expanded nardilysin-like peptidase gene family. The third is sex determination, where we could identify only a single homolog of the feminizer gene. As other ants and the honeybee have duplications of this gene, we hypothesize that this may partly explain the frequent production of diploid male larvae in A. echinatior. The fourth is the evolution of eusociality, where we find a highly conserved ant-specific profile of neuropeptide genes that may be related to caste determination. These first analyses of the A. echinatior genome indicate that considerable genetic changes are likely to have accompanied the transition from hunter-gathering to agricultural food production 50 million years ago, and the transition from single to multiple queen mating 10 million years ago.

The Oman exotics : a key to the understanding of the Neotethyan geodynamic evolution

The study of the exotic blocks of the Hawasina Nappes (Sultanate of Oman) leads to give apposit data that allow us to propose a new paleogeographic evolution of the Oman margin in time and space. A revised classification of exotic blocks into different paleogeographical units is presented. Two newly introduced stratigraphic groups, the Ramaq Group (Ordovician to Triassic) and the Al Buda'ah Group (upper Permian to Jurassic) are interpreted as tilted blocks related to the Oman continental margin. The Kawr Group (middle Triassic to Cretaceous) is redefined and interpreted as an atoll-type seamount. The paleogeography and paleoenvironments of these units are integrated into a new scheme of the Neotethyan rifting history. Brecciae and olisto¬liths of the Hawasina series are interpreted to have originated from tectonic movements affecting the Oman margin and the Neotethyan ocean floor. The breccias of late Permian age were generated by the extension processes affecting the margin, and by the creation of the Neotethyan oceanic floor. The breccias of mid-late Triassic age coincide in time with the collision of the Cimmerian continents with Eurasia. In constrast, the breccias of late Jurassic and Cretaceous age are interpreted as resulting to the creation of a new oceanic crust (Semail) off the Oman margin