SecA alone can promote protein translocation and ion channel activity: SecYEG increases efficiency and signal peptide specificity

SecA is an essential component of the Sec-dependent protein translocation pathway across cytoplasmic membranes in bacteria. Escherichia coli SecA binds to cytoplasmic membranes at SecYEG high affinity sites and at phospholipid low affinity sites. It has been widely viewed that SecYEG functions as the essential protein-conducting channel through which precursors cross the membranes in bacterial Sec-dependent pathways, and that SecA functions as a motor to hydrolyze ATP in translocating precursors through SecYEG channels. We have now found that SecA alone can promote precursor translocation into phospholiposomes. Moreover, SecA-liposomes elicit ionic currents in Xenopus oocytes. Patch-clamp recordings further show that SecA alone promotes signal peptide- or precursor-dependent single channel activity. These activities were observed with the functional SecA at about 1-2 μM. The results show that SecA alone is sufficient to promote protein translocation into liposomes and to elicit ionic channel activity at the phospholipids low affinity binding sites, thus indicating that SecA is able to form the protein-conducting channels. Even so, such SecA-liposomes are less efficient than those with a full complement of Sec proteins, and lose the signal-peptide proofreading function, resembling the effects of PrlA mutations. Addition of purified SecYEG restores the signal peptide specificity and increases protein translocation and ion channel activities. These data show that SecA can promote protein translocation and ion channel activities both when it is bound to lipids at low affinity sites and when it is bound to SecYEG with high affinity. The latter of the two interactions confers high efficiency and specificity.     

The molecular and mathematical basis of Waddington's epigenetic landscape: A framework for post‐Darwinian biology?

The Neo-Darwinian concept of natural selection is plausible when one assumes a straightforward causation of phenotype by genotype. However, such simple 1:1 mapping must now give place to the modern concepts of gene regulatory networks and gene expression noise. Both can, in the absence of genetic mutations, jointly generate a diversity of inheritable randomly occupied phenotypic states that could also serve as a substrate for natural selection. This form of epigenetic dynamics challenges Neo-Darwinism. It needs to incorporate the non-linear, stochastic dynamics of gene networks. A first step is to consider the mathematical correspondence between gene regulatory networks and Waddington's metaphoric 'epigenetic landscape', which actually represents the quasi-potential function of global network dynamics. It explains the coexistence of multiple stable phenotypes within one genotype. The landscape's topography with its attractors is shaped by evolution through mutational re-wiring of regulatory interactions - offering a link between genetic mutation and sudden, broad evolutionary changes.     

The role of TWEAK/Fn14 in cardiac remodeling

The pathophysiological basis of heart failure is cardiac remodeling, a process that comprises structural and functional changes including cardiomyocyte proliferation, hypertrophy, necrosis, apoptosis, autophagy, interstitial fibrosis, contractile dysfunction and ventricular dilatation. Accumulating evidence demonstrate that tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is involved in the process by binding its receptor fibroblast growth factor-inducible molecule 14 (Fn14). In this review, we will discuss the potential role of the TWEAK/Fn14 axis in cardiac remodeling, elucidate its possible mechanisms and explore new therapeutic targets for heart failure.     

Involvement of protein kinase A activation and phospholipase A(2) inhibition in the adenosine-activated basolateral 50 pS K(+) channels in the thick ascending limb of the rat kidney

The present study was designed to investigate the role of protein kinase A (PKA) and phospholipase A(2) (PLA(2)) in the stimulating effect of adenosine on the basolateral 50 pS K(+) channels in the thick ascending limb (TAL) of the rat kidney. Under the anatomic microscope, the TAL was dissected. The current of 50 pS K(+) channels were recorded by patch clamp technology. The protein expression of phosphorylated PKA and phosphorylated PLA(2) were examined by Western blot. The results showed that cyclohexyladenosine (CHA), an analog of adenosine, increased the 50 pS K(+) channel activity (P < 0.05). In the presence of H8, an antagonist of PKA, CHA did not affect the 50 pS K(+) channel activity. In the presence of AACOCF3 (an antagonist of PLA(2)), CHA did not further increase the 50 pS K(+) channel activity. CHA increased phosphorylation level of PKA, whereas inhibited phosphorylation of PLA(2) in the TAL of the rat kidney (P < 0.01). Furthermore, after blocking the PLA(2) with AACOCF3, CHA still increased the expression of phosphorylated PKA. On the contrary, CHA did not obviously change the expression of phosphorylated PLA(2) after H8 pretreatment. The results suggest that the stimulation of basolateral 50 pS K(+) channels by CHA is mediated by the activation of PKA followed by the inhibition of PLA(2) in the TAL of the rat kidney.     

Human Anti-CCR4 Minibody Gene Transfer for the Treatment of Cutaneous T-Cell Lymphoma

Background

Although several therapeutic options have become available for patients with Cutaneous T-cell Lymphoma (CTCL), no therapy has been curative. Recent studies have demonstrated that CTCL cells overexpress the CC chemokine receptor 4 (CCR4).

Methodology/Principal Findings

In this study, a xenograft model of CTCL was established and a recombinant adeno-associated viral serotype 8 (AAV8) vector expressing a humanized single-chain variable fragment (scFv)-Fc fusion (scFvFc or “minibody”) of anti-CCR4 monoclonal antibody (mAb) h1567 was evaluated for curative treatment. Human CCR4⁺ tumor-bearing mice treated once with intravenous infusion of AAV8 virions encoding the h1567 (AAV8-h1567) minibody showed anti-tumor activity in vivo and increased survival. The AAV8-h1567 minibody notably increased the number of tumor-infiltrating Ly-6G⁺ FcγRIIIa(CD16A)⁺ murine neutrophils in the tumor xenografts over that of AAV8-control minibody treated mice. Furthermore, in CCR4⁺ tumor-bearing mice co-treated with AAV8-h1567 minibody and infused with human peripheral blood mononuclear cells (PBMCs), marked tumor infiltration of human CD16A⁺ CD56⁺ NK cells was observed. The h1567 minibody also induced in vitro ADCC activity through both mouse neutrophils and human NK cells.

Conclusions/Significance

Overall, our data demonstrate that the in vivo anti-tumor activity of h1567 minibody is mediated, at least in part, through CD16A⁺ immune effector cell ADCC mechanisms. These data further demonstrate the utility of the AAV-minibody gene transfer system in the rapid evaluation of candidate anti-tumor mAbs and the potency of h1567 as a potential novel therapy for CTCL.     

Genome Analysis of Mycobacterium massiliense Strain M172, Which Contains a Putative Mycobacteriophage

The genome of Mycobacterium massiliense M172, isolated from a human sputum sample, was sequenced using Illumina GA IIX technology and found to contain 5,204,460 bp, including putative genes for virulence and antibiotic resistance as well as a 92-kb genomic region most likely to correspond to a mycobacteriophage.     

Genomic Analysis of Mycobacterium massiliense Strain M115, an Isolate from Human Sputum

We report the draft genome sequence of a clinical isolate, strain M115, identified as Mycobacterium massiliense, a member of the newly created taxon of Mycobacterium abscessus subspecies bolletii comb. nov.     

Genome sequence of Mycobacterium massiliense M18, isolated from a lymph node biopsy specimen

Mycobacterium massiliense is a rapidly growing mycobacterial species. The pathogenicity of this subspecies is not well known. We report here the annotated genome sequence of M. massiliense strain M18, which was isolated from a lymph node biopsy specimen from a Malaysian patient suspected of having tuberculous cervical lymphadenitis.