Fe65-PTB2 Dimerization Mimics Fe65-APP Interaction

Physiological function and pathology of the Alzheimer’s disease causing amyloid precursor protein (APP) are correlated with its cytosolic adaptor Fe65 encompassing a WW and two phosphotyrosine-binding domains (PTBs). The C-terminal Fe65-PTB2 binds a large portion of the APP intracellular domain (AICD) including the GYENPTY internalization sequence fingerprint. AICD binding to Fe65-PTB2 opens an intra-molecular interaction causing a structural change and altering Fe65 activity. Here we show that in the absence of the AICD, Fe65-PTB2 forms a homodimer in solution and determine its crystal structure at 2.6 Å resolution. Dimerization involves the unwinding of a C-terminal α-helix that mimics binding of the AICD internalization sequence, thus shielding the hydrophobic binding pocket. Specific dimer formation is validated by nuclear magnetic resonance (NMR) techniques and cell-based analyses reveal that Fe65-PTB2 together with the WW domain are necessary and sufficient for dimerization. Together, our data demonstrate that Fe65 dimerizes via its APP interaction site, suggesting that besides intra- also intermolecular interactions between Fe65 molecules contribute to homeostatic regulation of APP mediated signaling.

Synthesis of Highly Selective Submicromolar Microcystin-Based Inhibitors of Protein Phosphatase (PP)2A over PP1

Research and therapeutic targeting of the phosphoserine/threonine phosphatases PP1 and PP2A is hindered by the lack of selective inhibitors. The microcystin (MC) natural toxins target both phosphatases with equal potency, and their complex synthesis has complicated structure–activity relationship studies in the past. We report herein the synthesis and biochemical evaluation of 11 MC analogues, which was accomplished through an efficient strategy combining solid‐ and solution‐phase approaches. Our approach led to the first MC analogue with submicromolar inhibitory potency that is strongly selective for PP2A over PP1 and does not require the complex lipophilic Adda group. Through mutational and structural analyses, we identified a new key element for binding, as well as reasons for the selectivity. This work gives unprecedented insight into how selectivity between these phosphatases can be achieved with MC analogues.

[Input of a laboratory in the management of patients with Ebola virus disease and in the training of health personnel: experience of the Forecariah Ebola treatment centre (Guinea) in 2015]

Ebola virus disease (EVD) is associated with a high lethality rate even when the afflicted are provided with good support in an Ebola treatment center (ETC). Basic laboratory tests can help to better understand the pathophysiology of the disease, to guide treatment and to establish simple protocols and procedures tailored to the practice of medicine in the context of such precarious environment for caregivers. Based on a few clinical cases of patients treated in the ETC of Forecariah, Guinea, run by the French Red Cross, this article describes the difficult conditions associated with the provision of medical practice in this challenging environment, aiming to minimize the casualties in the EVD patient and to train the health staff.

Exploration of pathomechanisms triggered by a single-nucleotide polymorphism in titin's I-band: the cardiomyopathy-linked mutation T2580I

Missense single-nucleotide polymorphisms (mSNPs) in titin are emerging as a main causative factor of heart failure. However, distinguishing between benign and disease-causing mSNPs is a substantial challenge. Here, we research the question of whether a single mSNP in a generic domain of titin can affect heart function as a whole and, if so, how. For this, we studied the mSNP T2850I, seemingly linked to arrhythmogenic right ventricular cardiomyopathy (ARVC). We used structural biology, computational simulations and transgenic muscle in vivo methods to track the effect of the mutation from the molecular to the organismal level. The data show that the T2850I exchange is compatible with the domain three-dimensional fold, but that it strongly destabilizes it. Further, it induces a change in the conformational dynamics of the titin chain that alters its reactivity, causing the formation of aberrant interactions in the sarcomere. Echocardiography of knock-in mice indicated a mild diastolic dysfunction arising from increased myocardial stiffness. In conclusion, our data provide evidence that single mSNPs in titin's I-band can alter overall muscle behaviour. Our suggested mechanisms of disease are the development of non-native sarcomeric interactions and titin instability leading to a reduced I-band compliance. However, understanding the T2850I-induced ARVC pathology mechanistically remains a complex problem and will require a deeper understanding of the sarcomeric context of the titin region affected.

Resolving the α-glycosidic linkage of arginine-rhamnosylated translation elongation factor P triggers generation of the first ArgRha specific antibody

A previously discovered posttranslational modification strategy - arginine rhamnosylation - is essential for elongation factor P (EF-P) dependent rescue of polyproline stalled ribosomes in clinically relevant species such as Pseudomonas aeruginosa and Neisseria meningitidis. However, almost nothing is known about this new type of N-linked glycosylation. In the present study we used NMR spectroscopy to show for the first time that the α anomer of rhamnose is attached to Arg32 of EF-P, demonstrating that the corresponding glycosyltransferase EarP inverts the sugar of its cognate substrate dTDP-β-l-rhamnose. Based on this finding we describe the synthesis of an α-rhamnosylated arginine containing peptide antigen in order to raise the first anti-rhamnosyl arginine specific antibody (anti-Arg^Rha). Using ELISA and Western Blot analyses we demonstrated both its high affinity and specificity without any cross-reactivity to other N-glycosylated proteins. Having the anti-Arg^Rha at hand we were able to visualize endogenously produced rhamnosylated EF-P. Thus, we expect the antibody to be not only important to monitor EF-P rhamnosylation in diverse bacteria but also to identify further rhamnosyl arginine containing proteins. As EF-P rhamnosylation is essential for pathogenicity, our antibody might also be a powerful tool in drug discovery.

When Misery Loves Categorical Company: Accessibility of the Individual Self as a Moderator in Category-Based Representation of Attractive and Unattractive In-Groups

In two experiments, the role of the accessibility of the individual self as a moderator variable in processing information about attractive or unattractive in-groups was examined. An indicator of category-based in-group representation served as the main dependent variable. In Experiment 1, the authors predicted and found an interaction between accessibility of the individual self and in-group attractiveness. People exhibited more category-based representations for unattractive than for attractive in-groups when accessibility was low, but the opposite trend was observed when accessibility was high. Experiment 2 showed that the difference in category-based representations of unattractive versus attractive in-groups, given low accessibility of the individual self: depends also on relative in-group size. Here, only majority members, but not minority members, showed the critical effect. The results are discussed in terms of group members' self-evaluation concerns.

Helping Individuals or Group Members? The Role of Individual and Collective Identification in AIDS Volunteerism

This article presents a group-level perspective on helping that was tested in the context of AIDS volunteerism. It was predicted and found that homosexuals were more willing to volunteer when collective identification in terms of sexual orientation was high. The opposite trend was found for heterosexuals. Also as predicted, homosexuals were less willing to volunteer when identification as a unique individual was high, whereas the opposite was again true for heterosexuals. Thus, AIDS volunteerism emerged as a form of intragroup helping for homosexuals and as a form of interindividual helping for heterosexuals. In addition, identification with the AIDS volunteer service organization proved to be a positive predictor of AIDS volunteerism regardless of sexual orientation. Finally, two individual motivations emerged as positive predictors, namely, gaining knowledge and understanding emerged for homosexuals and expressing humanitarian values emerged for heterosexuals. The results are summarized in a dual-pathway model of volunteerism.

MRI during radiotherapy of glioblastoma : Does MRI allow for prognostic stratification?

AIM

To evaluate the role of magnetic resonance imaging (MRI) as a predictor for the clinical course in patients with glioblastoma.

PATIENTS AND METHODS

In 64 patients with glioblastoma undergoing (chemo)radiotherapy MRI studies were obtained before radiation, after 30 gray (Gy), after 60 Gy and during follow-up. MRI findings were assigned to categories: definite progression, questionable progression, no change. Patients were followed clinically.

RESULTS

At 30 Gy, 23 of 64 patients (36 %) demonstrated definite (dp; n = 15) or questionable (qp; n = 8) progression; in 41/64 (64 %) no change was found compared with preradiation MRI. After radiotherapy at 60 Gy, 26 of 64 (41 %) patients showed dp (n = 18) or qp (n = 8). In 2 cases with qp at the 30 Gy MRI, progress was unquestionable in the 60 Gy MRI study. In the 64 patients, 5 of the 60 Gy MRIs showed dp/qp after being classified as no change at the 30 Gy MRI, 2 of the 30 Gy MRIs showed qp, while the 60 Gy MRI showed tumour regression and 3 fulfilled the criteria for pseudoprogression during ongoing radiotherapy. The 30 Gy study allowed for prognostic stratification: dp/qp compared to stable patients showed median survival of 10.5 versus 20 months.

CONCLUSION

MR follow-up after 30 Gy in patients undergoing (chemo)radiotherapy for glioblastoma allows prognostic appraisal. Pseudoprogression has to be taken into account, though rare in our setting. Based on these findings, early discussion of treatment modification is possible.

Abstract P2-11-12: Novel protocol combining metronomic nant-paclitaxel with HER2-targeted natural killer cells (innate immunotherapy) for HER2-positive metastatic breast cancer

Background. Natural killer (NK) cells are an important effector cell type for adoptive cancer immunotherapy. Phase 1 clinical trials in patients with advanced cancers demonstrated the safety of unmodified, activated NK-92 cells (aNK), with no evidence of cytokine storm from 18 infusions delivered over 6 months; clinical responses were observed in a subset of patients. Like T cells, NK cells can be engineered to express chimeric antigen receptors (CARs) to enhance their antitumor activity. A stable clonal HER2-specific NK-92 cell line (HER2.taNK) mediated selective and sequential killing of HER2-expressing MDA-MB-453 cells in vitro (Schönfeld. MolTher. 2015;23:330-338). In addition, HER2.taNK cells were enriched in MDA-MB-453/EGFP xenografts and reduced the number of pulmonary metastasis in a renal cell carcinoma model, suggesting that HER2.taNK cells are a promising clinical candidate for use in adoptive cancer immunotherapy. Metronomic (low-dose, continuous) chemotherapy can be more effective than high-dose therapy in patients with advanced breast cancer (Montagna. Canc. Treat. Rev. 2014;40:922-950). Here we evaluate HER2.taNK cells in combination with metronomic nant-paclitaxel (lyophilized polymeric micellar formulation of paclitaxel) in a mouse model of HER2-positive breast cancer to determine the feasibility of a human clinical trial of HER2.taNK in combination with metronomic nant-paclitaxel.

Methods. HER2.taNK cells were generated as described previously (Schönfeld. MolTher. 2015;23:330-338). MDA-MB-453 cells were implanted into the mammary fat pads of female nude mice. When tumors reached 100 mm3, mice were divided into 6 groups of 5 mice and dosed (IV) with saline (10 mL/kg, qd x 15), nant-paclitaxel (2.5-4 mg/kg q2d x 15), γ-irradiated (5 Gy) HER2.taNK cells (1 x 107 cells, days 1, 3, 5, and 8), or nant-paclitaxel + γ-irradiated (5 Gy) HER2.taNK cells–γ-irradiation is a potential safety measure for clinical application and prevents HER2.taNK cell replication while preserving antitumor activity. Tumor size and animal weights were measured every other day post-implantation.

Results: Results obtained 20 days post-treatment are shown in the table. Nant-paclitaxel alone and HER2.taNK alone significantly inhibited tumor growth. The combination of nant-paclitaxel + HER2.taNK led to significant tumor regressions (p<0.05).

Treatment Dose T/C (%) P-ValueSalinenant-paclitaxel5 mg/kg-26.7 P < 0.05 (vs saline) HER2.taNK1 x 107 cells-22.2 P < 0.05 (vs saline)nant-paclitaxel +5 mg/kg +-60.0P < 0.05 (vs nant-paclitaxel)HER2.taNK1 x 107 cellsP < 0.05 (vs HER2.taNK)

Conclusions: Single agent nant-paclitaxel and HER2.taNK were similarly effective at inhibiting tumor growth in this mouse model of HER2+ breast cancer. The combination of nant-paclitaxel + HER2.taNK appeared to be synergistic resulting in tumor regressions and significantly better efficacy vs each agent alone. This study illustrates the potential for combining metronomic low-dose chemotherapy with NK-based immunotherapy in a clinical trial of patients with metastatic breast cancer.

Citation Format: Rabizadeh S, Simon B, Klingemann H, Sims D, Weiss R, Soon-Shiong P. Novel protocol combining metronomic nant-paclitaxel with HER2-targeted natural killer cells (innate immunotherapy) for HER2-positive metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-11-12.

When less equal is less human: Intragroup (dis)respect and the experience of being human

Past research has demonstrated that equality-based respect is an important antecedent of positive social interaction and group-serving behavior. In the present research we tested whether intragroup equality-based respect affects perceptions of being treated as a human as well as self-dehumanization. In Experiment 1, we found that high respect received from fellow work group members heightens group members' sense of being treated as a human being, while low respect diminishes it. In Experiment 2, we secured evidence that (dis)respect also affected recipients' self-views in terms of self-dehumanization. More specifically, if respect was withheld by other ingroup members, fewer human nature and human uniqueness traits, as well as secondary positive emotions, were attributed to the self. This increase in self-infrahumanization was further related to higher endorsement of unethical behavior. We discuss the importance of equality-based respect for (de-)humanization processes in social groups.

Tolerance as a function of disapproval and respect: The case of Muslims

The article assesses a disapproval-respect model of tolerance according to which tolerance is made possible when disapproval of others' beliefs, preferences, or practices is balanced by respect for them as equal fellow citizens. Employing a sample of Muslims living in Germany, we predicted and found that such respect was more predictive of outgroup toleration when respondents disapproved rather than approved of the outgroups' beliefs, preferences, or practices. Moreover, respondents who displayed the critical combination of extreme disapproval and full respect indeed showed outgroup toleration. A parallel pattern of results was observed for willingness to engage in intergroup cooperation. Practical implications are discussed.

The structure of the SOLE element of oskar mRNA

mRNA localization by active transport is a regulated process that requires association of mRNPs with protein motors for transport along either the microtubule or the actin cytoskeleton. oskar mRNA localization at the posterior pole of the Drosophila oocyte requires a specific mRNA sequence, termed the SOLE, which comprises nucleotides of both exon 1 and exon 2 and is assembled upon splicing. The SOLE folds into a stem-loop structure. Both SOLE RNA and the exon junction complex (EJC) are required for oskar mRNA transport along the microtubules by kinesin. The SOLE RNA likely constitutes a recognition element for a yet unknown protein, which either belongs to the EJC or functions as a bridge between the EJC and the mRNA. Here, we determine the solution structure of the SOLE RNA by Nuclear Magnetic Resonance spectroscopy. We show that the SOLE forms a continuous helical structure, including a few noncanonical base pairs, capped by a pentanucleotide loop. The helix displays a widened major groove, which could accommodate a protein partner. In addition, the apical helical segment undergoes complex dynamics, with potential functional significance.

The structure of the SOLE element of oskar mRNA

mRNA localization by active transport is a regulated process that requires association of mRNPs with protein motors for transport along either the microtubule or the actin cytoskeleton. oskar mRNA localization at the posterior pole of the Drosophila oocyte requires a specific mRNA sequence, termed the SOLE, which comprises nucleotides of both exon 1 and exon 2 and is assembled upon splicing. The SOLE folds into a stem-loop structure. Both SOLE RNA and the exon junction complex (EJC) are required for oskar mRNA transport along the microtubules by kinesin. The SOLE RNA likely constitutes a recognition element for a yet unknown protein, which either belongs to the EJC or functions as a bridge between the EJC and the mRNA. Here, we determine the solution structure of the SOLE RNA by Nuclear Magnetic Resonance spectroscopy. We show that the SOLE forms a continuous helical structure, including a few noncanonical base pairs, capped by a pentanucleotide loop. The helix displays a widened major groove, which could accommodate a protein partner. In addition, the apical helical segment undergoes complex dynamics, with potential functional significance.

RNA structure determination by solid-state NMR spectroscopy

Knowledge of the RNA three-dimensional structure, either in isolation or as part of RNP complexes, is fundamental to understand the mechanism of numerous cellular processes. Because of its flexibility, RNA represents a challenge for crystallization, while the large size of cellular complexes brings solution-state NMR to its limits. Here, we demonstrate an alternative approach on the basis of solid-state NMR spectroscopy. We develop a suite of experiments and RNA labeling schemes and demonstrate for the first time that ssNMR can yield a RNA structure at high-resolution. This methodology allows structural analysis of segmentally labelled RNA stretches in high-molecular weight cellular machines—independent of their ability to crystallize— and opens the way to mechanistic studies of currently difficult-to-access RNA-protein assemblies.

The determination of RNA structures within high-molecular weight protein-RNA complexes in non-crystalline state is technically challenging. Here, the authors describe a solid-state NMR protocol for the determination of RNA structures at high resolution.

Reaching across group boundaries: Respect from outgroup members facilitates recategorization as a common group

Two laboratory experiments tested the hypothesis that (equality-based) respect from outgroup members facilitates recategorization of the original ingroup and outgroup as a common group. In Experiment 1, we varied respect from outgroup members (low vs. medium vs. high) and measured recipients' willingness to recategorize. As predicted, high respect from an outgroup source increased willingness to recategorize as a common group relative to low respect. In Experiment 2, we orthogonally varied respect (low vs. medium vs. high) and its source (ingroup members vs. outgroup members) and employed a more differentiated recategorization measure including an intermediate or nested-group option (i.e., two subgroups of a common group). While the recategorization effect of high versus low respect from outgroup members was replicated, no such effect was observed for respect from ingroup members. Instead, there was some indication that, when it comes from ingroup members, a medium level of respect may be optimal for inducing a shift towards recategorization as a common group. Implications of the present research for the conceptualization of respect are discussed.

Introduction of a metabolic joint asymmetry score derived from conventional bone scintigraphy. A new tool to differentiate psoriatic from rheumatoid arthritis

AIM

Clinical differentiation of psoriatic arthritis (PsA) and rheumatoid arthritis (rA) based on the pattern of joint involvement can be difficult; the frequent form of PsA with polyarthritis of the peripheral joints may sometime resemble rA. We investigated a metabolic joint asymmetry score (MJAS), reflecting the overall asymmetric joint involvement on conventional bone scintigraphy, for differentiating PsA from rA in patients presenting with peripheral polyarthritis.

PATIENTS, METHODS

106 patients (n = 61, PsA; n = 45, rA) with peripheral polyarthritis (≥ 5 joints) as well as 26 control subjects with no history of chronic joint disorders were analyzed. The intensity of articular 99mTc-MDP uptake in 40 peripheral joint pairs was scored regarding the bilateral difference of each joint based on a scale of 0-2 (no significant, moderate, and marked asymmetry, respectively). The patient's MJAS was defined as the sum of uptake difference scores of all joint pairs. The association of MJAS with the underlying condition (Psoriasis criteria, Revised Criteria of the ACR) was examined.

RESULTS

5280 peripheral joint pairs were investigated. There was no significant difference in the total number of involved joints in PsA 15.0 ± 8.2 versus rA 17.5 ± 8.8 patients (p = 0.132), but significantly less involvement in the control group (6.7 ± 5.0, p < 0.001). MJAS was markedly higher in PsA (17.0 ± 9.6) than in rA (4.8 ± 3.9, p < 0.001), and correlated with the total number of involved joints in PsA (r = 0.516, p < 0.001), but not in rA (r = 0.078, p = 0.380). The MJAS disparity between PsA and rA persisted after exclusion of the DIP joints (14.4 ± 7.7 vs. 4.4 ± 3.3; p<0.001).

CONCLUSIONS

The new reproducible semi-quantification method for the asymmetry of metabolic joint involvement permits differentiation of psoriatic from rheumatoid peripheral arthritis with MJAS being markedly higher in patients with PsA as compared to rA patients. The score may offer an effective complementary tool for characterizing patients with peripheral polyarthritis.

Structural Analysis of Protein-RNA Complexes in Solution Using NMR Paramagnetic Relaxation Enhancements

Biological activity in the cell is predominantly mediated by large multiprotein and protein-nucleic acid complexes that act together to ensure functional fidelity. Nuclear magnetic resonance (NMR) spectroscopy is the only method that can provide information for high-resolution three-dimensional structures and the conformational dynamics of these complexes in solution. Mapping of binding interfaces and molecular interactions along with the characterization of conformational dynamics is possible for very large protein complexes. In contrast, de novo structure determination by NMR becomes very time consuming and difficult for protein complexes larger than 30 kDa as data are noisy and sparse. Fortunately, high-resolution structures are often available for individual domains or subunits of a protein complex and thus sparse data can be used to define their arrangement and dynamics within the assembled complex. In these cases, NMR can therefore be efficiently combined with complementary solution techniques, such as small-angle X-ray or neutron scattering, to provide a comprehensive description of the structure and dynamics of protein complexes in solution. Particularly useful are NMR-derived paramagnetic relaxation enhancements (PREs), which provide long-range distance restraints (ca. 20Å) for structural analysis of large complexes and also report on conformational dynamics in solution. Here, we describe the use of PREs from sample production to structure calculation, focusing on protein-RNA complexes. On the basis of recent examples from our own research, we demonstrate the utility, present protocols, and discuss potential pitfalls when using PREs for studying the structure and dynamic features of protein-RNA complexes.

Optical polymers with tunable refractive index for nanoimprint technologies

In order to realize a versatile high throughput production of micro-optical elements, UV-curable polymer composites containing titanium dioxide nanoparticles were prepared and characterized. The composites are based on an industrial prototype epoxy polymer. Titanium dioxide nanoparticles smaller than 10 nm were synthesized by the nonaqueous sol method and in situ sterically stabilized by three different organic surfactants. The composites exhibit high transparency. Distinct alteration of optical transmission properties for visible light and near IR wavelength range could be avoided by adaption of the stabilizing organic surfactant. Most importantly, the refractive index (RI) of the composites that depends on the fraction of incorporated inorganic nanoparticles could be directly tuned. E.g. the RI at a wavelength of 635 nm of a composite containing 23 wt% titanium dioxide nanoparticles is increased to 1.626, with respect to a value of 1.542 for the pure polymer. Furthermore, it could be demonstrated that the prepared inorganic-organic nanocomposites are well suited for the direct fabrication of low-cost micro-optical elements by nanoimprint lithography. A low response of the optical composite properties to temperature treatment up to 220 °C with a shrinkage of only about 4% ensures its application for integrated micro-optical elements in industrial production.

NMR approaches for structural analysis of multidomain proteins and complexes in solution

NMR spectroscopy is a key method for studying the structure and dynamics of (large) multidomain proteins and complexes in solution. It plays a unique role in integrated structural biology approaches as especially information about conformational dynamics can be readily obtained at residue resolution. Here, we review NMR techniques for such studies focusing on state-of-the-art tools and practical aspects. An efficient approach for determining the quaternary structure of multidomain complexes starts from the structures of individual domains or subunits. The arrangement of the domains/subunits within the complex is then defined based on NMR measurements that provide information about the domain interfaces combined with (long-range) distance and orientational restraints. Aspects discussed include sample preparation, specific isotope labeling and spin labeling; determination of binding interfaces and domain/subunit arrangements from chemical shift perturbations (CSP), nuclear Overhauser effects (NOEs), isotope editing/filtering, cross-saturation, and differential line broadening; and based on paramagnetic relaxation enhancements (PRE) using covalent and soluble spin labels. Finally, the utility of complementary methods such as small-angle X-ray or neutron scattering (SAXS, SANS), electron paramagnetic resonance (EPR) or fluorescence spectroscopy techniques is discussed. The applications of NMR techniques are illustrated with studies of challenging (high molecular weight) protein complexes.

Profile of incident chronic kidney disease related-mineral bone disorders in chronic kidney disease Stage 4 and 5: A hospital based cross-sectional survey

Chronic kidney disease related-mineral bone disorder (CKD-MBD) has been poorly studied in pre-dialysis Indian CKD patients. We aimed to study the clinical, biochemical and extra skeletal manifestations of untreated CKD-MBD in pre-dialysis Stage 4 and 5 CKD patients attending nephrology out-patient clinic at a tertiary care hospital in South India. A hospital based cross-sectional survey including, demographic profile, history of CKD-MBD symptoms, measurement of serum calcium, phosphate, parathyroid hormone, 25 hydroxy vitamin D (25(OH) D) and alkaline phosphatase; lateral abdominal X-rays for abdominal aortic calcification (AAC) and echocardiography for valvular calcification (VC) was carried out. Of the 710 patients surveyed, 45% had no CKD-MBD related symptom. Prevalence of hypocalcemia, hyperphosphatemia, hyperparathyroidism (>150 pg/mL) and 25(OH) D levels <30 ng/mL was 66.3%, 59%, 89.3% and 74.7% respectively. Echocardiography was carried out in 471 patients; 96% of whom had VC (calcification score ≥1). Patients with VC were older and had lower 25(OH) D levels than those without. Lateral abdominal X-rays were obtained in 558 patients, 6.8% of whom were found to have AAC, which was associated with older age. Indian patients with incident CKD-MBD have a high prevalence of hypocalcemia, 25(OH) D deficiency and VC even prior to initiating dialysis while AAC does not appear to be common. The association between 25(OH) D deficiency and VC needs further exploration.

¹H, ¹³C, and ¹⁵N chemical shift assignments of the phosphotyrosine binding domain 2 (PTB2) of human FE65

Phosphotyrosine binding domains (PTB) are protein-protein interaction domains that play important roles in various cellular signal transduction pathways. The second phosphotyrosine binding domain (PTB2) of the human scaffolding protein FE65 interacts with the C-terminal part of the Amyloid Precursor Protein (APP) involved in Alzheimer's disease. The structure of PTB2 in complex with a 32 amino acid fragment of APP has been solved previously by X-ray crystallography. Here, we report the NMR spectral assignments of the free FE65 PTB2. This provides the basis for further investigation of the interactions of PTB2 with peptides and small organic ligands with the aim of disrupting the PTB2-APP interaction.

Tomographic diffractive microscopy and multiview profilometry with flexible aberration correction

We have developed a tomographic diffractive microscope in reflection, which permits observation of sample surfaces with an improved lateral resolution, compared to a conventional holographic microscope. From the same set of data, high-precision measurements can be performed on the shape of the reflective surface by reconstructing the phase of the diffracted field. Doing so allows for several advantages compared to classical holographic interferometric measurements: improvement in lateral resolution, easier phase unwrapping, reduction of the coherent noise, combined with the high-longitudinal precision provided by interferometric phase measurements. We demonstrate these capabilities by imaging various test samples.

The structure of the box C/D enzyme reveals regulation of RNA methylation

Post-transcriptional modifications are essential to the cell life cycle, as they affect both pre-ribosomal RNA processing and ribosome assembly. The box C/D ribonucleoprotein enzyme that methylates ribosomal RNA at the 2'-O-ribose uses a multitude of guide RNAs as templates for the recognition of rRNA target sites. Two methylation guide sequences are combined on each guide RNA, the significance of which has remained unclear. Here we use a powerful combination of NMR spectroscopy and small-angle neutron scattering to solve the structure of the 390 kDa archaeal RNP enzyme bound to substrate RNA. We show that the two methylation guide sequences are located in different environments in the complex and that the methylation of physiological substrates targeted by the same guide RNA occurs sequentially. This structure provides a means for differential control of methylation levels at the two sites and at the same time offers an unexpected regulatory mechanism for rRNA folding.

Functional role of the flexible N-terminal extension of FKBP38 in catalysis

FKBP38 regulates apoptosis through unique interactions with multiple regulators including Bcl-2. Interestingly, the peptidylprolyl isomerase activity of FKBP38 is only detectable when it binds to calcium-saturated calmodulin (CaM/Ca²⁺). This, in turn, permits the formation of a complex with Bcl-2. FKBP38 thereby provides an important link between isomerase activity and apoptotic pathways. Here, we show that the N-terminal extension (residues 1-32) preceding the catalytic domain of FKBP38 has an autoinhibitory activity. The core isomerase activity of FKBP38 is inhibited by transient interactions involving the flexible N-terminal extension that precedes the catalytic domain. Notably, CaM/Ca²⁺ binds to this N-terminal extension and thereby releases the autoinhibitory contacts between the N-terminal extension and the catalytic domain, thus potentiating the isomerase activity of FKBP38. Our data demonstrate how CaM/Ca²⁺ modulates the catalytic activity of FKBP38.

Association of human cytomegalovirus DNAaemia and specific granzyme B responses in lung transplant recipients

In lung transplant recipients (LTRs), human cytomegalovirus (HCMV) DNAaemia could be associated with HCMV disease and reduced allograft survival. In the present study we analysed whether or not HCMV-specific granzyme B (Grz-B) responses indicating CD8(+) T cell cytotoxicity exert an impact on HCMV DNAaemia and relate to specific interferon (IFN)-γ secretion. HCMV-specific Grz-B responses were quantitated by enzyme-linked immunosorbent assay (ELISA) in 70 samples from 39 HCMV seropositive LTRs who were prospectively investigated for HCMV DNA plasma levels and IFN-γ kinetics using a standardized CD8(+) T cell assay (QuantiFERON®-CMV assay). In all LTRs who were protected from HCMV DNAaemia by early and persistent IFN-γ responses, Grz-B responses were also detected. In LTRs who developed episodes of HCMV DNAaemia, the Grz-B responses which were detected prior to viral DNA detection differed significantly in patients who experienced episodes with high (exceeding 1000 copies/ml) and low plasma DNA levels (P = 0·0290, Fisher's exact test). Furthermore, the extent of Grz-B release prior to viral DNAaemia correlated statistically with the detected levels of IFN-γ (P < 0·0001, Spearman's rank test). Of note, simultaneous detection of Grz-B and IFN-γ secretion was associated significantly with protection from high HCMV DNA plasma levels during the subsequent follow-up (P = 0·0057, Fisher's exact test), and this association was stronger than for IFN-γ detection alone. We conclude that, in addition to IFN-γ responses, Grz-B secretion by CD8(+) T cells is essential to control HCMV replication and a simultaneous measurement of IFN-γ and Grz-B could contribute to the immune monitoring of LTRs.

A reducing milieu renders cofilin insensitive to phosphatidylinositol 4,5-bisphosphate (PIP2) inhibition

Oxidative stress can lead to T cell hyporesponsiveness. A reducing micromilieu (e.g. provided by dendritic cells) can rescue T cells from such oxidant-induced dysfunction. However, the reducing effects on proteins leading to restored T cell activation remained unknown. One key molecule of T cell activation is the actin-remodeling protein cofilin, which is dephosphorylated on serine 3 upon T cell costimulation and has an essential role in formation of mature immune synapses between T cells and antigen-presenting cells. Cofilin is spatiotemporally regulated; at the plasma membrane, it can be inhibited by phosphatidylinositol 4,5-bisphosphate (PIP₂). Here, we show by NMR spectroscopy that a reducing milieu led to structural changes in the cofilin molecule predominantly located on the protein surface. They overlapped with the PIP₂- but not actin-binding sites. Accordingly, reduction of cofilin had no effect on F-actin binding and depolymerization and did not influence the cofilin phosphorylation state. However, it did prevent inhibition of cofilin activity through PIP₂. Therefore, a reducing milieu may generate an additional pool of active cofilin at the plasma membrane. Consistently, in-flow microscopy revealed increased actin dynamics in the immune synapse of untransformed human T cells under reducing conditions. Altogether, we introduce a novel mechanism of redox regulation: reduction of the actin-remodeling protein cofilin renders it insensitive to PIP₂ inhibition, resulting in enhanced actin dynamics.

Efficient detection of hydrogen bonds in dynamic regions of RNA by sensitivity-optimized NMR pulse sequences

Improved Sensitivity: Efficient NMR experiments are presented for determining the secondary structure in large and dynamic RNAs using J-couplings across hydrogen bonds. The experiments provide up to eight-fold improved sensitivity and thus enable detection of base pairs in dynamic regions even in large RNAs.

Structural principles of RNA catalysis in a 2'-5' lariat-forming ribozyme

RNA-catalyzed lariat formation is present in both eukaryotes and prokaryotes. To date we lack structural insights into the catalytic mechanism of lariat-forming ribozymes. Here, we study an artificial 2'-5' AG1 lariat-forming ribozyme that shares the sequence specificity of lariat formation with the pre-mRNA splicing reaction. Using NMR, we solve the structure of the inactive state of the ribozyme in the absence of magnesium. The reaction center 5'-guanosine appears to be part of a helix with an exceptionally widened major groove, while the lariat-forming A48 is looped out at the apex of a pseudoknot. The model of the active state built by mutational analysis, molecular modeling, and small-angle X-ray scattering suggests that A48 is recognized by a conserved adenosine, juxtaposed to the 5'-guanosine in one base-pair step distance, while the G1-N7 coordinates a magnesium ion essential for the activation of the nucleophile. Our findings offer implications for lariat formation in RNA enzymes including the mechanism of the recognition of the branch-site adenosine.