A potent and selective non-peptide antagonist of the neurokinin A (NK2) receptor.

SR 48968 is a potent and selective non-peptide antagonist of the neurokinin A (NK2) receptor. SR 48968 selectively inhibited neurokinin A binding to its receptor and was a competitive antagonist of neurokinin A-mediated contraction of different isolated smooth muscle preparations from various species including human. In vivo, the compound inhibited the bronchoconstriction induced by neurokinin A in guinea pigs. SR 48968 can be used to study the physiological or pathological role of neurokinin A and may be useful in the treatment of neurokinin A-dependent pathology.     

Viruslike particles containing knob-associated histidine-rich protein are secreted into the culture medium of Plasmodium falciparum in vitro cultures

This report describes the isolation of a viruslike particle from in vitro cultures of the human malaria parasite P. falciparum. Electronmicroscopic observations suggest that the particles are liberated into the culture medium by budding from the erythrocyte membrane. The density of the free particles is 1.16, they contain nucleic acid and two distinct molecular species of the knob-associated Histidine-rich protein. Proteins of the particles are recognized by sera from malaria patients. The previously described knobs may correspond to viral coats inserted in the membrane.     

A simple reverse genetics method to generate recombinant coronaviruses

Engineering recombinant viruses is a pre‐eminent tool for deciphering the biology of emerging viral pathogens such as the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). However, the large size of coronavirus genomes renders the current reverse genetics methods challenging. Here, we describe a simple method based on “infectious subgenomic amplicons” (ISA) technology to generate recombinant infectious coronaviruses with no need for reconstruction of the complete genomic cDNA and apply this method to SARS‐CoV‐2 and also to the feline enteric coronavirus. In both cases we rescue wild‐type viruses with biological characteristics similar to original strains. Specific mutations and fluorescent red reporter genes can be readily incorporated into the SARS‐CoV‐2 genome enabling the generation of a genomic variants and fluorescent reporter strains for in vivo experiments, serological diagnosis, and antiviral assays. The swiftness and simplicity of the ISA method has the potential to facilitate the advance of coronavirus reverse genetics studies, to explore the molecular biological properties of the SARS‐CoV‐2 variants, and to accelerate the development of effective therapeutic reagents.     

Dynamics of marine bacterial and phytoplankton populations using multiplex liquid bead array technology

Heterotrophic bacteria and phytoplankton dominate the biomass and play major roles in the biogeochemical cycles of the surface ocean. Here, we designed and tested a fast, high‐throughput and multiplexed hybridization‐based assay to detect populations of marine heterotrophic bacteria and phytoplankton based on their small subunit ribosomal DNA sequences. The assay is based on established liquid bead array technology, an approach that is gaining acceptance in biomedical research but remains underutilized in ecology. End‐labelled PCR products are hybridized to taxon‐specific oligonucleotide probes attached to fluorescently coded beads followed by flow cytometric detection. We used ribosomal DNA environmental clone libraries (a total of 450 clones) and cultured isolates to design and test 26 bacterial and 10 eukaryotic probes specific to various ribotypes and genera of heterotrophic bacteria and eukaryotic phytoplankton. Pure environmental clones or cultures were used as controls and demonstrated specificity of the probes to their target taxa. The quantitative nature of the assay was demonstrated by a significant relationship between the number of target molecules and fluorescence signal. Clone library sequencing and bead array fluorescence from the same sample provided consistent results. We then applied the assay to a 37‐day time series of coastal surface seawater samples from the Southern California Bight to examine the temporal dynamics of microbial communities on the scale of days to weeks. As expected, several bacterial phylotypes were positively correlated with total bacterial abundances and chlorophyll a concentrations, but others were negatively correlated. Bacterial taxa belonging to the same broad taxonomic groups did not necessarily correlate with one another, confirming recent results suggesting that inferring ecological role from broad taxonomic identity may not always be accurate.     

Defining the risks of mesenchymal stromal cell therapy

We address the issue of the potential for malignant transformation of cultured mesenchymal stromal cells (MSC) commonly used in clinical cell-therapy protocols and describe the culture conditions under which tumorigenesis is likely to be an extremely uncommon event.     

Hydration and protein folding in water and in reverse micelles: compressibility and volume changes

The partial specific volume and adiabatic compressibility of proteins reflect the hydration properties of the solvent-exposed protein surface, as well as changes in conformational states. Reverse micelles, or water-in-oil microemulsions, are protein-sized, optically-clear microassemblies in which hydration can be experimentally controlled. We explore, by densimetry and ultrasound velocimetry, three basic proteins: cytochrome c, lysozyme, and myelin basic protein in reverse micelles made of sodium bis (2-ethylhexyl) sulfosuccinate, water, and isooctane and in aqueous solvents. For comparison, we use beta-lactoglobulin (pI = 5.1) as a reference protein. We examine the partial specific volume and adiabatic compressibility of the proteins at increasing levels of micellar hydration. For the lowest water content compatible with complete solubilization, all proteins display their highest compressibility values, independent of their amino acid sequence and charge. These values lie within the range of empirical intrinsic protein compressibility estimates. In addition, we obtain volumetric data for the transition of myelin basic protein from its initially unfolded state in water free of denaturants, to a folded, compact conformation within the water-controlled microenvironment of reverse micelles. These results disclose yet another aspect of the protein structural properties observed in membrane-mimetic molecular assemblies.     

IgE receptor type I-dependent regulation of a Rab3D-associated kinase: a possible link in the calcium-dependent assembly of SNARE complexes

Following activation through high affinity IgE receptors (FcepsilonRI), mast cells release, within a few minutes, their granule content of inflammatory and allergic mediators. FcepsilonRI-induced degranulation is a SNARE (soluble N-ethylmaleimide attachment protein receptors)-dependent fusion process. It is regulated by Rab3D, a subfamily member of Rab GTPases. Evidence exists showing that Rab3 action is calcium-regulated although the molecular mechanisms remain unclear. To obtain an understanding of Rab3D function we have searched for Rab3D-associated effectors that respond to allergic triggering through FcepsilonRI. Using the RBL-2H3 mast cell line we detected a Ser/Thr kinase activity, termed here Rak3D (from Rab3D-associated kinase), because it was specifically co-immunoprecipitated with anti-Rab3D antibody. Rak3D activity, as measured by its auto- or transphosphorylation, was maximal in resting cells and decreased upon stimulation. The down-regulation of the observed activity was blocked with EGTA, but not with other degranulation inhibitors, suggesting that its activity functions downstream of calcium influx. We found that Rak3D phosphorylates the NH(2)-terminal regulatory domain of the t-SNARE syntaxin 4, but not syntaxin 2 or 3. The phosphorylation of syntaxin 4 decreased its binding to its partner SNAP23. Thus, we propose a novel phosphorylation-dependent mechanism by which Rab3D controls SNARE assembly in a calcium-dependent manner.     

Structural evidence for a functional role of human tissue nonspecific alkaline phosphatase in bone mineralization

The human tissue nonspecific alkaline phosphatase (TNAP) is found in liver, kidney, and bone. Mutations in the TNAP gene can lead to Hypophosphatasia, a rare inborn disease that is characterized by defective bone mineralization. TNAP is 74% homologous to human placental alkaline phosphatase (PLAP) whose crystal structure has been recently determined at atomic resolution (Le Du, M. H., Stigbrand, T., Taussig, M. J., Ménez, A., and Stura, E. A. (2001) J. Biol. Chem, 276, 9158-9165). The degree of homology allowed us to build a reliable TNAP model to investigate the relationship between mutations associated with hypophosphatasia and their probable consequences on the activity or the structure of the enzyme. The mutations are clustered within five crucial regions, namely the active site and its vicinity, the active site valley, the homodimer interface, the crown domain, and the metal-binding site. The crown domain and the metal-binding domain are mammalian-specific and were observed for the first time in the PLAP structure. The crown domain contains a collagen binding loop. A synchrotron radiation x-ray fluorescence study confirms that the metal in the metal-binding site is a calcium ion. Several severe mutations in TNAP occur around this calcium site, suggesting that calcium may be of critical importance for the TNAP function. The presence of this extra metal-binding site gives new insights on the controversial role observed for calcium.