Nestboxes and immigration drive the growth of an urban Peregrine Falcon Falco peregrinus population

Drivers of wildlife population dynamics are generally numerous and interacting. Some of these drivers may impact demographic processes that are difficult to estimate, such as immigration into the focal population. Populations may furthermore be small and subject to demographic stochasticity. All of these factors contribute to blur the causal relationship between past management action and current population trends. The urban Peregrine Falcon Falco peregrinus population in Cape Town, South Africa, increased from three pairs in 1997 to 18 pairs in 2010. Nestboxes were installed over this period to manage the interface between new urban pairs of Falcons and the human users of colonized buildings, and incidentally to improve breeding success. We used integrated population models (IPMs) formally to combine information from a capture–mark–recapture study, monitoring of reproductive success and counts of population size. As all local demographic processes were directly observed, the IPM approach also allowed us to estimate immigration by difference. The provision of nestboxes, as a possible stimulant of population growth, improved breeding success and accounted for an estimated 3–26% of the population increase. The most important driver of growth, however, was immigration. Despite low sample sizes, the IPM approach allowed us to obtain relatively precise estimates of the population‐level impact of nestbox deployment. The goal of conservation interventions is often to increase population size, so the effectiveness of such interventions should ideally be assessed at the population level. IPMs are powerful tools in this context for combining demographic information that may be limited due to small population size or practical constraints on monitoring. Our study quantitatively documented both the immigration process that led to growth of a small population and the effect of a management action that helped the process.     

Channelrhodopsin unchained: Structure and mechanism of a light-gated cation channel

The new and vibrant field of optogenetics was founded by the seminal discovery of channelrhodopsin, the first light-gated cation channel. Despite the numerous applications that have revolutionised neurophysiology, the functional mechanism is far from understood on the molecular level. An arsenal of biophysical techniques has been established in the last decades of research on microbial rhodopsins. However, application of these techniques is hampered by the duration and the complexity of the photoreaction of channelrhodopsin compared with other microbial rhodopsins. A particular interest in resolving the molecular mechanism lies in the structural changes that lead to channel opening and closure. Here, we review the current structural and mechanistic knowledge that has been accomplished by integrating the static structure provided by X-ray crystallography and electron microscopy with time-resolved spectroscopic and electrophysiological techniques. The dynamical reactions of the chromophore are effectively coupled to structural changes of the protein, as shown by ultrafast spectroscopy. The hierarchical sequence of structural changes in the protein backbone that spans the time range from 10^− 12 s to 10^− 3 s prepares the channel to open and, consequently, cations can pass. Proton transfer reactions that are associated with channel gating have been resolved. In particular, glutamate 253 and aspartic acid 156 were identified as proton acceptor and donor to the retinal Schiff base. The reprotonation of the latter is the critical determinant for channel closure. The proton pathway that eventually leads to proton pumping is also discussed. This article is part of a Special Issue entitled: Retinal Proteins — You can teach an old dog new tricks.     

Mutual structural effect of bilirubin and model membranes by vibrational circular dichroism

In this study, vibrational circular dichroism (VCD) spectroscopy was employed for the first time to study the bilirubin (BR) interaction with model membranes and models for membrane proteins. An enantioselective interaction of BR with zwitterionic 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and sphingomyelin (SPM) liposomes was observed by VCD and electronic circular dichroism (ECD) complemented by absorption and fluorescence spectroscopy. The M-form of BR was preferentially recognized in the BR/DMPC system at concentration above 1 × 10^− 4 M, for lower concentrations the P-form of BR was recognized by the DMPC liposomes. The VCD spectra also showed that the SPM liposomes, which represent the main component of nerve cell membrane, were significantly more disturbed by the presence of BR than the DMPC liposomes—a stable association with a strong VCD signal was observed providing the explanations for the supposed BR neurotoxicity. The effect of time and pH on the BR/DMPC or SPM liposome systems was shown to be essential while the effect of temperature in the range of 15–70 °C was negligible demonstrating the surprisingly high temperature stability of BR when interacting with the studied membranes. The influence of a membrane protein was tested on a model consisting of poly-l-arginine (PLAG) bound in the α-helical form to the surface of 1,2-dimyristoyl-sn-glycero-3-phospho-(1′-rac-glycerol) liposomes and sodium dodecyl sulfate micelles. VCD and also ECD spectra showed that a variety of BR diastereoisomers interacted with PLAG in such systems. In a system of PLAG with micelles composed of sodium dodecyl sulfate, the M-form of bound BR was observed.     

Influence of the scaffolding protein Zonula Occludens (ZOs) on membrane channels

Zonula Occludens (ZO) proteins are ubiquitous scaffolding proteins providing the structural basis for the assembly of multiprotein complexes at the cytoplasmic surface of the plasma membrane and linking transmembrane proteins to the filamentous cytoskeleton. They belong to the large family of membrane-associated guanylate kinase (MAGUK)-like proteins comprising a number of subfamilies based on domain content and sequence similarity. ZO proteins were originally described to localize specifically to tight junctions, or Zonulae Occludentes, but this notion was rapidly reconsidered since ZO proteins were found to associate with adherens junctions as well as with gap junctions, particularly with connexin-made intercellular channels, and also with a few other membrane channels. Accumulating evidence reveals that in addition to having passive scaffolding functions in organizing gap junction complexes, including connexins and cytoskeletals, ZO proteins (particularly ZO-1) also actively take part in the dynamic function as well as in the remodeling of junctional complexes in a number of cellular systems. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.     

S100 to receptor for advanced glycation end-products binding assay: Looking for inhibitors

Secreted by tumor and stromal cells, S100 proteins exert their biological functions via the interaction with surface receptors. The most described receptor is the receptor for advanced glycation end-products (RAGE), thereby participating in the S100-dependent cell migration, invasion, tumor growth, angiogenesis and metastasis. Several approaches have been described for determining this interaction. Here we describe an easy, specific and highly reproducible ELISA-based method, by optimizing several parameters such as the binding and blocking buffer, interaction time and concentrations, directed to screen chemical and biological inhibitors of this interaction for S100A4, S100A7 and S100P proteins. The efficiency of the protocol was validated by using well described neutralizing agents of the RAGE receptor and of the S100A4 activity. The methodology described here will allow future works with other members of the S100 protein family and their receptors.     

Small molecule glutaminase inhibitors block glutamate release from stimulated microglia

Glutaminase plays a critical role in the generation of glutamate, a key excitatory neurotransmitter in the CNS. Excess glutamate release from activated macrophages and microglia correlates with upregulated glutaminase suggesting a pathogenic role for glutaminase. Both glutaminase siRNA and small molecule inhibitors have been shown to decrease excess glutamate and provide neuroprotection in multiple models of disease, including HIV-associated dementia (HAD), multiple sclerosis and ischemia. Consequently, inhibition of glutaminase could be of interest for treatment of these diseases. Bis-2-(5-phenylacetimido-1,2,4-thiadiazol-2-yl)ethyl sulfide (BPTES) and 6-diazo-5-oxo-l-norleucine (DON), two most commonly used glutaminase inhibitors, are either poorly soluble or non-specific. Recently, several new BPTES analogs with improved physicochemical properties were reported. To evaluate these new inhibitors, we established a cell-based microglial activation assay measuring glutamate release. Microglia-mediated glutamate levels were significantly augmented by tumor necrosis factor (TNF)-α, phorbol 12-myristate 13-acetate (PMA) and Toll-like receptor (TLR) ligands coincident with increased glutaminase activity. While several potent glutaminase inhibitors abrogated the increase in glutamate, a structurally related analog devoid of glutaminase activity was unable to block the increase. In the absence of glutamine, glutamate levels were significantly attenuated. These data suggest that the in vitro microglia assay may be a useful tool in developing glutaminase inhibitors of therapeutic interest.     

Bovine alpha-2-HS-glycoprotein functions as a booster antigen for efficiently stimulating humoral immune responses to CCR5 and SIVmac239 envelope glycoprotein

The presence of anti-CCR5 and anti-HIV-1 envelope glycoprotein (ENV) gp41 antibodies (Abs) at sites of HIV-1 exposure was effective in preventing its transmission to HIV-1-exposed seronegative (ESN) subjects. Here, we design an immunogen that can induce Abs against CCR5 and SIVmac239 ENV simultaneously and show that bovine alpha-2-HS-glycoprotein (bAHSG) functions as a booster antigen for efficiently stimulating humoral immune responses to CCR5 and ENV. Initially, we generated a rhesus CCR5-derived cyclopeptide (cDDR5) conjugated with a recombinant trimeric SIVmac239 Env. When inguinally administered to rhesus macaques, the immunogen simultaneously induced both anti-CCR5 and anti-ENV Abs in sera, and the purified serum IgG fraction exerted an inhibitory effect on SIVmac239 infection in vitro. When further boosted with bAHSG, the responses of both Abs were significantly enhanced. To examine the cross-reactivity of bAHSG, it was administered to naïve cynomolgus macaques. The results showed a statistically significant increase in IgG response against cynomolgus CCR5 and SIVmac239 ENV, and the induction of neutralizing activity against SIVmac239. These findings suggest that bAHSG is useful for immune strategies aimed at generating Abs against CCR5 and ENV simultaneously to confer HIV-protective immunity.     

Effect and mechanism of the Ang-(1-7) on human mesangial cells injury induced by low density lipoprotein

Hyperlipidemia is an independent risk factor for renal disease, and lipid deposition is associated with glomerulosclerosis. The angiotensin converting enzyme 2-angiotensin-(1-7)-Mas axis (ACE2-Ang-(1-7)-Mas axis) has been reported to participate in lipid metabolic regulation but its mechanism remains unclear. We hypothesized Ang-(1-7) would reduce lipid uptake in human mesangial cells (HMCs) by regulating the low density lipoprotein receptor–sterol regulatory element binding proteins 2–SREBP cleavage activating protein (LDLr–SREBP2–SCAP) negative feedback system, and improve glomerulosclerosis by regulating the transforming growth factor-β1 (TGF-β1). In this study we found that ACE2 was undetected in HMCs. The administration of LDL caused normal LDLr–SREBPs–SCAP negative feedback effect. Exogenous Ang-(1-7) enhanced this negative feedback effect via down-regulating LDLr, SREBP2, and SCAP expression, and effectively inhibited LDL-induced lipid deposition and cholesterol increases. This enhanced inhibitory effect was reversed by the Mas receptor antagonist A-779. Meanwhile, Ang-(1-7) significantly decreased the high LDL-induced production of TGF-β1, an effect blocked by A-779. Interestingly, HMCs treated with Ang-(1-7) alone activated the TGF-β1 expression. Our results suggested that Ang-(1-7) inhibits LDL accumulation and decreases cholesterol levels via modulating the LDLr–SREBPs–SCAP negative feedback system through the Mas receptor. Moreover, Ang-(1-7) exhibits a dual regulatory effect on TGF-β1 in HMCs.     

Evaluation and identification of hepatitis B virus entry inhibitors using HepG2 cells overexpressing a membrane transporter NTCP

Hepatitis B virus (HBV) entry has been analyzed using infection-susceptible cells, including primary human hepatocytes, primary tupaia hepatocytes, and HepaRG cells. Recently, the sodium taurocholate cotransporting polypeptide (NTCP) membrane transporter was reported as an HBV entry receptor. In this study, we established a strain of HepG2 cells engineered to overexpress the human NTCP gene (HepG2-hNTCP-C4 cells). HepG2-hNTCP-C4 cells were shown to be susceptible to infection by blood–borne and cell culture-derived HBV. HBV infection was facilitated by pretreating cells with 3% dimethyl sulfoxide permitting nearly 50% of the cells to be infected with HBV. Knockdown analysis suggested that HBV infection of HepG2-hNTCP-C4 cells was mediated by NTCP. HBV infection was blocked by an anti-HBV surface protein neutralizing antibody, by compounds known to inhibit NTCP transporter activity, and by cyclosporin A and its derivatives. The infection assay suggested that cyclosporin B was a more potent inhibitor of HBV entry than was cyclosporin A. Further chemical screening identified oxysterols, oxidized derivatives of cholesterol, as inhibitors of HBV infection. Thus, the HepG2-hNTCP-C4 cell line established in this study is a useful tool for the identification of inhibitors of HBV infection as well as for the analysis of the molecular mechanisms of HBV infection.     

HUWE1 interacts with BRCA1 and promotes its degradation in the ubiquitin–proteasome pathway

The cellular BRCA1 protein level is essential for its tumor suppression activity and is tightly regulated through multiple mechanisms including ubiquitn–proteasome system. E3 ligases are involved to promote BRCA1 for ubiquitination and degradation. Here, we identified HUWE1/Mule/ARF-BP1 as a novel BRCA1-interacting protein involved in the control of BRCA1 protein level. HUWE1binds BRCA1 through its N-terminus degron domain. Depletion of HUWE1 by siRNA-mediated interference significantly increases BRCA1 protein levels and prolongs the half-life of BRCA1. Moreover, exogenous expression of HUWE1 promotes BRCA1 degradation through the ubiquitin–proteasome pathway, which could explain an inverse correlation between HUWE1 and BRCA1 levels in MCF10F, MCF7 and MDA-MB-231 breast cancer cells. Consistent with a functional role for HUWE1 in regulating BRCA1-mediated cellular response to DNA damage, depletion of HUWE1 by siRNA confers increased resistance to ionizing radiation and mitomycin. These data indicate that HUWE1 is a critical negative regulator of BRCA1 and suggest a new molecular mechanism for breast cancer pathogenesis.