Inter and intralaminar excitation of parvalbumin interneurons in mouse barrel cortex.

Parvalbumin (PV) interneurons are inhibitory fast-spiking cells with essential roles in directing the flow of information through cortical circuits. These neurons set the balance between excitation and inhibition and control rhythmic activity. PV interneurons differ between cortical layers in their morphology, circuitry, and function, but how their electrophysiological properties vary has received little attention. Here we investigate responses of PV interneurons in different layers of primary somatosensory barrel cortex (BC) to different excitatory inputs. With the genetically-encoded hybrid voltage sensor, hVOS, we recorded voltage changes in many L2/3 and L4 PV interneurons simultaneously, with stimulation applied to either L2/3 or L4. A semi-automated procedure was developed to identify small regions of interest corresponding to single responsive PV interneurons. Amplitude, half-width, and rise-time were greater for PV interneurons residing in L2/3 compared to L4. Stimulation in L2/3 elicited responses in both L2/3 and L4 with longer latency compared to stimulation in L4. These differences in latency between layers could influence their windows for temporal integration. Thus, PV interneurons in different cortical layers of BC respond in a layer specific and input specific manner, and these differences have potential roles in cortical computations.

Inter and Intralaminar Excitation of Parvalbumin Interneurons in Mouse Barrel Cortex.

Parvalbumin (PV) interneurons are inhibitory fast-spiking cells with essential roles in directing the flow of information through cortical circuits. These neurons set the balance between excitation and inhibition, control rhythmic activity, and have been linked to disorders including autism spectrum and schizophrenia. PV interneurons differ between cortical layers in their morphology, circuitry, and function, but how their electrophysiological properties vary has received little attention. Here we investigate responses of PV interneurons in different layers of primary somatosensory barrel cortex (BC) to different excitatory inputs. With the genetically-encoded hybrid voltage sensor, hVOS, we recorded voltage changes simultaneously in many L2/3 and L4 PV interneurons to stimulation in either L2/3 or L4. Decay-times were consistent across L2/3 and L4. Amplitude, half-width, and rise-time were greater for PV interneurons residing in L2/3 compared to L4. Stimulation in L2/3 elicited responses in both L2/3 and L4 with longer latency compared to stimulation in L4. These differences in latency between layers could influence their windows for temporal integration. Thus PV interneurons in different cortical layers of BC show differences in response properties with potential roles in cortical computations.

The interleukin-like epithelial-mesenchymal transition inducer ILEI exhibits a non-interleukin-like fold and is active as a domain-swapped dimer.

Production and secretion of pro-metastatic proteins is a feature of many tumor cells. The FAM3C interleukin-like epithelial-to-mesenchymal-transition (EMT) inducer (ILEI) has been shown to be strongly up-regulated in several cancers and to be essential for tumor formation and metastasis in epithelial cells, correlating with a significant decrease in overall survival in colon and breast cancer patients. ILEI has been seen to interact with the γ-secretase presenilin 1 subunit (PS1). However, not much is known about the mechanism-of-action or the detailed ILEI structure. We present here the crystal structures of FAM3C ILEI and show that it exists as monomers but also as covalent dimers. The observed ILEI ß-ß-α fold confirmed previous indications that the FAM3C proteins do not form classical four-helix-bundle structures as was initially predicted. This provides the first experimental evidence that the interleukin-like EMT inducers are not evolutionarily related to the interleukins. However, more surprisingly, the ILEI dimer structure was found to feature a trans-linked domain swap, converting an intramolecular disulfide to intermolecular. Interestingly, dimeric but not monomeric ILEI was subsequently found to cause a dose-dependent increase in EpRas cell invasiveness comparable with TGF-ß, indicating that the dimer might be the active ILEI species. This is in line with a parallel study showing that covalent oligomerization of ILEI is essential for EMT and tumor progression in vivo The structures and the activity data give some first insight into the relationship between dimerization and ILEI function as well as indicate an intriguing link between ILEI, the PS1-protease, TGF-ß, and the TGF-ß receptor 1.

Phototriggerable peptidomimetics for the inhibition of Mycobacterium tuberculosis ribonucleotide reductase by targeting protein-protein binding.

Incorporation of an artificial amino acid 2 with a stilbene chromophore into peptidomimetics with three to nine amino acids yields phototriggerable candidates for inhibition of the binding between the R1 and R2 subunits of the M. tuberculosis ribonucleotide reductase (RNR). Interstrand hydrogen bond probability was used as a guideline for predicting conformational preferences of the photoisomers. Binding of these inhibitors has been rationalized by docking studies with the R1 unit. Significant differences in binding of the photoisomers were observed. For the shorter peptidomimetics, stronger binding of the Z isomer might indicate hydrophobic interactions between the stilbene chromophore and the binding site.

DXR inhibition by potent mono- and disubstituted fosmidomycin analogues.

The antimalarial compound fosmidomycin targets DXR, the enzyme that catalyzes the first committed step in the MEP pathway, producing the essential isoprenoid precursors, isopentenyl diphosphate and dimethylallyl diphosphate. The MEP pathway is used by a number of pathogens, including Mycobacterium tuberculosis and apicomplexan parasites, and differs from the classical mevalonate pathway that is essential in humans. Using a structure-based approach, we designed a number of analogues of fosmidomycin, including a series that are substituted in both the Cα and the hydroxamate positions. The latter proved to be a stable framework for the design of inhibitors that extend from the polar and cramped (and so not easily druggable) substrate-binding site and can, for the first time, bridge the substrate and cofactor binding sites. A number of these compounds are more potent than fosmidomycin in terms of killing Plasmodium falciparum in an in vitro assay; the best has an IC50 of 40 nM.

Novel pseudopeptides incorporating a benzodiazepine-based turn mimetic--targeting Mycobacterium tuberculosis ribonucleotide reductase.

Peptides mimicking the C-terminus of the small subunit (R2) of Mycobacterium tuberculosis ribonucleotide reductase (RNR) can compete for binding to the large subunit (R1) and thus inhibit RNR activity. Moreover, it has been suggested that the binding of the R2 C-terminus is very similar in M. tuberculosis and Salmonella typhimurium. Based on modeling studies of a crystal structure of the holocomplex of the S. typhimurium enzyme, a benzodiazepine-based turn mimetic was identified and a set of novel compounds incorporating the benzodiazepine scaffold was synthesized. The compounds were evaluated in a competitive fluorescence polarization assay and in an RNR activity assay. These studies revealed that the compounds incorporating the benzodiazepine scaffold have the ability to compete for the M. tuberculosis R2 binding site with low-micromolar affinity.

Structure of alphacoronavirus transmissible gastroenteritis virus nsp1 has implications for coronavirus nsp1 function and evolution.

Coronavirus nsp1 has been shown to induce suppression of host gene expression and to interfere with the host immune response. However, the mechanism is currently unknown. The only available structural information on coronavirus nsp1 is the nuclear magnetic resonance (NMR) structure of the N-terminal domain of nsp1 from severe acute respiratory syndrome coronavirus (SARS-CoV) from the betacoronavirus genus. Here we present the first nsp1 structure from an alphacoronavirus, transmissible gastroenteritis virus (TGEV) nsp1. It displays a six-stranded ß-barrel fold with a long alpha helix on the rim of the barrel, a fold shared with SARS-CoV nsp1(13-128). Contrary to previous speculation, the TGEV nsp1 structure suggests that coronavirus nsp1s have a common origin, despite the lack of sequence homology. However, comparisons of surface electrostatics, shape, and amino acid conservation between the alpha- and betacoronaviruses lead us to speculate that the mechanism for nsp1-induced suppression of host gene expression might be different in these two genera.

Multimarker risk assessment including osteoprotegerin and CXCL16 in acute coronary syndromes.

OBJECTIVE: CXCL16 and osteoprotegerin (OPG) both predict mortality in acute coronary syndromes. We hypothesized that a combination of CXCL16 and OPG concentrations would add prognostic information to the Global Registry of Acute Coronary Events (GRACE) score in patients hospitalized for acute coronary syndromes. METHODS AND RESULTS: We assessed the associations between circulating OPG and soluble CXCL16 levels, obtained within 24 hours of admission (day 1) and after 3 months, and mortality, heart failure and reinfarction in 1322 patients admitted with acute coronary syndromes. After adjustment for the GRACE score, medication, diabetes mellitus and sex, the combination of high values (fourth quartile) for OPG and CXCL16 at baseline was associated with increased short-term (3 months) cardiovascular mortality (hazard ratio, 3.28; 95% CI, 1.84-5.82; P<0.0001). The combined high values were also significantly associated with the long-term (median 91 months) prognosis after adjustment, with hazard ratios 2.18 for cardiovascular mortality (95% CI, 1.62-2.92; P<0.0001), and 2.22 for heart failure (95% CI, 1.67-2.96; P<0.0001). These long-term associations remained significant after further adjustment for left ventricular ejection fraction, C-reactive protein, and pro B-type natriuretic peptide. For 635 patients with blood samples within 24 hours and at 3 months, the combination of high CXCL16 and OPG values (fourth quartile) in the early or stable phase was of a similar order associated with mortality and morbidity beyond 3 months. CONCLUSIONS: Circulating CXCL16 and OPG are independent predictors of long-term mortality and heart failure development in acute coronary syndromes patients, even after extensive adjustments. Their combination gives more information than either marker alone.

Synthesis of functionalized cinnamaldehyde derivatives by an oxidative Heck reaction and their use as starting materials for preparation of Mycobacterium tuberculosis 1-deoxy-D-xylulose-5-phosphate reductoisomerase inhibitors.

Cinnamaldehyde derivatives were synthesized in good to excellent yields in one step by a mild and selective, base-free palladium(II)-catalyzed oxidative Heck reaction starting from acrolein and various arylboronic acids. Prepared α,ß-unsaturated aldehydes were used for synthesis of novel α-aryl substituted fosmidomycin analogues, which were evaluated for their inhibition of Mycobacterium tuberculosis 1-deoxy-D-xylulose 5-phosphate reductoisomerase. IC(50) values between 0.8 and 27.3 µM were measured. The best compound showed activity comparable to that of the most potent previously reported α-aryl substituted fosmidomycin-class inhibitor.

Structure and functionality in flavivirus NS-proteins: perspectives for drug design.

Flaviviridae are small enveloped viruses hosting a positive-sense single-stranded RNA genome. Besides yellow fever virus, a landmark case in the history of virology, members of the Flavivirus genus, such as West Nile virus and dengue virus, are increasingly gaining attention due to their re-emergence and incidence in different areas of the world. Additional environmental and demographic considerations suggest that novel or known flaviviruses will continue to emerge in the future. Nevertheless, up to few years ago flaviviruses were considered low interest candidates for drug design. At the start of the European Union VIZIER Project, in 2004, just two crystal structures of protein domains from the flaviviral replication machinery were known. Such pioneering studies, however, indicated the flaviviral replication complex as a promising target for the development of antiviral compounds. Here we review structural and functional aspects emerging from the characterization of two main components (NS3 and NS5 proteins) of the flavivirus replication complex. Most of the reviewed results were achieved within the European Union VIZIER Project, and cover topics that span from viral genomics to structural biology and inhibition mechanisms. The ultimate aim of the reported approaches is to shed light on the design and development of antiviral drug leads.

Structure of the methyltransferase domain from the Modoc virus, a flavivirus with no known vector.

The Modoc virus (MODV) is a flavivirus with no known vector (NKV). Evolutionary studies have shown that the viruses in the MODV group have evolved in association with mammals (bats, rodents) without transmission by an arthropod vector. MODV methyltransferase is the first enzyme from this evolutionary branch to be structurally characterized. The high-resolution structure of the methyltransferase domain of the MODV NS5 protein (MTase(MODV)) was determined. The protein structure was solved in the apo form and in complex with its cofactor S-adenosyl-L-methionine (SAM). Although it belongs to a separate evolutionary branch, MTase(MODV) shares structural characteristics with flaviviral MTases from the other branches. Its capping machinery is a relatively new target in flaviviral drug development and the observed structural conservation between the three flaviviral branches indicates that it may be possible to identify a drug that targets a range of flaviviruses. The structural conservation also supports the choice of MODV as a possible model for flavivirus studies.

Soluble CXCL16 predicts long-term mortality in acute coronary syndromes.

BACKGROUND: CXCL16/SR-PSOX is an interferon-gamma-regulated chemokine and scavenger receptor for oxidized low-density lipoprotein that is expressed in atherosclerotic lesions. Proteolytic cleavage of membrane-bound CXCL16 releases soluble CXCL16, which may promote migration of effector T cells and augment a proatherogenic inflammatory response. We hypothesized that soluble CXCL16 concentrations are associated with long-term outcome in patients with acute coronary syndromes. METHODS AND RESULTS: We assessed the association between circulating CXCL16 levels obtained within 24 hours after admission and time to death in 1351 patients (median age 67 years, 30% female) with a diagnosis of unstable angina, non-ST-segment-elevation myocardial infarction, or ST-segment-elevation myocardial infarction. During a median follow-up time of 81 months, 377 patients died. Increased levels of CXCL16 were prognostically unfavorable; the fourth versus first quartile was associated with higher risk of death (hazard ratio 2.1; 95% CI 1.6 to 2.8; P<0.0001), triple risk of developing heart failure (hazard ratio 3.0; 95% CI 1.8 to 5.1; P<0.0001), and a doubling of the risk of rehospitalization for myocardial infarction (hazard ratio 2.1; 95% CI 1.3 to 3.3; P=0.002). After adjustment for conventional risk markers, logarithmically transformed CXCL16 level remained a strong independent indicator of long-term mortality (hazard ratio 1.21; 95% CI 1.09 to 1.36 per 1 SD increase in CXCL16; P=0.0006) and congestive heart failure development (hazard ratio 1.25; 95% CI 1.05 to 1.48; P=0.01). In a subsample of 714 patients, after further adjustment for troponin T, high-sensitive C-reactive protein, pro-B-type natriuretic peptide, and left ventricular ejection fraction, CXCL16 still provided significant additional prognostic information on mortality (hazard ratio 1.21; 95% CI 1.02 to 1.42 per 1 SD increase in CXCL16; P=0.02). CONCLUSIONS: In patients with an acute coronary syndrome, CXCL16 levels obtained within 24 hours of admission are associated with long-term mortality after adjustment for other risk factors.

Prognostic value of circulating chromogranin A levels in acute coronary syndromes.

AIMS: To determine whether circulating levels of chromogranin A (CgA) provide prognostic information independently of conventional risk markers in acute coronary syndromes (ACSs). METHODS AND RESULTS: We measured circulating CgA levels on day 1 in 1268 patients (median age 67 years, 70% male) with ACS admitted to a single coronary care unit of a Scandinavian teaching hospital. The merit of CgA as a biomarker was evaluated after adjusting for conventional cardiovascular risk factors. During a median follow-up of 92 months, 389 patients (31%) died. The baseline CgA concentration was strongly associated with increased long-term mortality [hazard ratio per 1 standard deviation increase in logarithmically transformed CgA level: 1.57 (1.44-1.70), P < 0.001], heart failure hospitalizations [1.54 (1.35-1.76), P < 0.001], and recurrent myocardial infarction (MI) [1.27 (1.10-1.47), P < 0.001], but not stroke. After adjustment for conventional cardiovascular risk markers, the association remained significant for mortality [hazard ratio 1.28 (1.15-1.42), P < 0.001] and heart failure hospitalization [hazard ratio 1.24 (1.04-1.47), P = 0.02], but not recurrent MI. CONCLUSION: CgA is an independent predictor of long-term mortality and heart failure hospitalizations across the spectrum of ACSs and provides incremental prognostic information to conventional cardiovascular risk markers.

Circulating osteoprotegerin levels and long-term prognosis in patients with acute coronary syndromes.

OBJECTIVES: This study was designed to assess the association between osteoprotegerin (OPG) levels on admission and long-term prognosis in patients with acute coronary syndromes (ACS). BACKGROUND: Osteoprotegerin, a member of the tumor necrosis factor receptor superfamily, has pleiotropic effects on bone metabolism, endocrine function, and the immune system. METHODS: Serum samples for OPG analysis were obtained within 24 h of admission in 897 ACS patients (median age 66 years, 71% men) and related to the incidence of death, heart failure (HF) hospitalizations, myocardial infarction (MI), and stroke. RESULTS: A total of 261 patients died during a median follow-up of 89 months. The baseline OPG concentration was strongly associated with increased long-term mortality (hazard ratio [HR] for HR per 1 SD increase in logarithmically transformed OPG level 1.7 [range 1.5 to 1.9] p < 0.0001) and HF hospitalizations (HR 2.0 [range 1.6 to 2.5]; p < 0.0001) but weaker with recurrent MI (HR 1.3 [range 1.0 to 1.5]; p = 0.02) and not with stroke (HR 1.2 [range 0.9 to 1.6]; p = 0.35). After adjustment for conventional risk markers, including troponin I, C-reactive protein (CRP), B-type natriuretic peptide (BNP), and ejection fraction, the association remained significant for mortality (HR 1.4 [range 1.2 to 1.7]; p < 0.0001) and HF hospitalization (HR 1.6 [range 1.2 to 2.1]; p = 0.0002), but not recurrent MI. By comparison of the area under the receiver-operating characteristics curves, OPG performed similarly to BNP and ejection fraction and significantly better than CRP and troponin I as a predictor of death. CONCLUSIONS: Serum OPG is strongly predictive of long-term mortality and HF development in patients with ACS, independent of conventional risk markers.