Blood pressure homeostasis is maintained by a P311-TGF-β axis

P311 is an 8-kDa intracellular protein that is highly conserved across species and is expressed in the nervous system as well as in vascular and visceral smooth muscle cells. P311-null (P311(–/–)) mice display learning and memory defects, but alterations in their vasculature have not been previously described. Here we report that P311(–/–) mice are markedly hypotensive with accompanying defects in vascular tone and VSMC contractility. Functional abnormalities in P311(–/–) mice resulted from decreased total and active levels of TGF-β1, TGF-β2, and TGF-β3 that arise as a specific consequence of decreased translation. Vascular hypofunctionality was fully rescued in vitro and in vivo by exogenous TGF-β1–TGF-β3. Conversely, P311-transgenic (P311(TG)) mice had elevated levels of TGF-β1–TGF-β3 and subsequent hypertension. Consistent with findings attained in mouse models, arteries recovered from hypertensive human patients displayed increased P311 expression. Thus, we identified P311 as the first protein known to modulate TGF-β translation and the first pan-regulator of TGF-β expression under steady-state conditions. Together, our findings point to P311 as a critical blood pressure regulator and establish a potential link between P311 expression and the development of hypertensive disease

A third lineage with two-piece tmRNA

tmRNA combines tRNA and mRNA properties and helps bacteria to cope with stalled ribosomes. Its termini normally pair in the tRNA domain, closing the mRNA portion into a looping domain. A striking variation is a two-piece form that effectively breaks open the mRNA domain loop, resulting from independent gene permutation events in alphaproteobacteria and cyanobacteria. Convergent evolution to a similar form in separate bacterial lineages suggests that loop-opening benefits tmRNA function. This argument is strengthened by the discovery of a third bacterial lineage with a loop-opened two-piece tmRNA. Whereas most betaproteobacteria have one-piece tmRNA, a permuted tmRNA gene was found for Dechloromonas aromatica and close relatives. Correspondingly, two tmRNA pieces were identified, at approximately equal abundance and at a level one-fifteenth that of ribosomes, a 189 nt mRNA piece and a 65 nt aminoacylatable piece. Together these pieces were active with purified Escherichia coli translational components, but not alone. The proposed secondary structure combines common tmRNA features differently from the structures of other two-piece forms. The origin of the gene is unclear; horizontal transfer may be indicated by the similarity of the tRNA domain to that from a cyanobacterial two-piece tmRNA, but such transfer would not appear simple since the mRNA domain is most similar to that of other betaproteobacteria

Genomic Insights into Drug Resistance Determinants in Cedecea neteri, A Rare Opportunistic Pathogen

Cedecea, a genus in the Enterobacteriaceae family, includes several opportunistic pathogens reported to cause an array of sporadic acute infections, most notably of the lung and bloodstream. One species, Cedecea neteri, is associated with cases of bacteremia in immunocompromised hosts and has documented resistance to different antibiotics, including β-lactams and colistin. Despite the potential to inflict serious infections, knowledge about drug resistance determinants in Cedecea is limited. In this study, we utilized whole-genome sequence data available for three environmental strains (SSMD04, M006, ND14a) of C. neteri and various bioinformatics tools to analyze drug resistance genes in this bacterium. All three genomes harbor multiple chromosome-encoded β-lactamase genes. A deeper analysis of β-lactamase genes in SSMD04 revealed four metallo-β-lactamases, a novel variant, and a CMY/ACT-type AmpC putatively regulated by a divergently transcribed AmpR. Homologs of known resistance-nodulation-cell division (RND)-type multidrug efflux pumps such as OqxB, AcrB, AcrD, and MdtBC were also identified. Genomic island prediction for SSMD04 indicated that tolC, involved in drug and toxin export across the outer membrane of Gram-negative bacteria, was acquired by a transposase-mediated genetic transfer mechanism. Our study provides new insights into drug resistance mechanisms of an environmental microorganism capable of behaving as a clinically relevant opportunistic pathogen

Characterization of Two Novel AmpC Beta-Lactamases from the Emerging Opportunistic Pathogen, <i>Cedecea neteri</i>

The genus Cedecea (family Enterobacteriaceae) causes a wide spectrum of acute infections in immunocompromised hosts, from pneumonia and bacteremia to oral ulcers and dialysis-related peritonitis. While Cedecea infections are reported infrequently in the literature, documented clinical cases of this emerging opportunistic human pathogen have occurred worldwide. Cedecea neteri has clinical significance and exhibits antimicrobial drug resistance. However, little is known about the molecular basis underlying the resistance phenotypes in C. neteri. We previously hypothesized that the open-reading frame cnt10470 in the C. neteri SSMD04 genome encodes a chromosomal Ambler class C (AmpC) β-lactamase based on sequence homology. In this study, recombinant polyhistidine-tagged proteins were created by cloning the putative ampC genes from SSMD04 and C. neteri ATCC 33855 (a clinical isolate) into the pET-6xHN expression vector, overexpressing the proteins, and then purifying the recombinant AmpCs (rAmpCs) using immobilized metal affinity chromatography (Ni-NTA). The in vitro enzymatic analysis of the purified rAmpCs was performed to determine the Km and kcat for various β-lactam substrates. The rAmpCs are functional class C β-lactamases when assayed using the chromogenic β-lactamase substrate, nitrocefin. The presence of functional AmpCs in both C. neteri strains underscores the necessity of performing antibiotic susceptibility testing in the management of C. neteri infections