Expression and activity of the calcitonin receptor family in a sample of primary human high-grade gliomas

Background

Glioblastoma (GBM) is the most common and aggressive type of primary brain cancer. With median survival of less than 15 months, identification and validation of new GBM therapeutic targets is of critical importance.

Results

In this study we tested expression and performed pharmacological characterization of the calcitonin receptor (CTR) as well as other members of the calcitonin family of receptors in high-grade glioma (HGG) cell lines derived from individual patient tumours, cultured in defined conditions.

Previous immunohistochemical data demonstrated CTR expression in GBM biopsies and we were able to confirm CALCR (gene encoding CTR) expression. However, as assessed by cAMP accumulation assay, only one of the studied cell lines expressed functional CTR, while the other cell lines have functional CGRP (CLR/RAMP1) receptors. The only CTR-expressing cell line (SB2b) showed modest coupling to the cAMP pathway and no activation of other known CTR signaling pathways, including ERK_1/2 and p38 MAP kinases, and Ca²⁺ mobilization, supportive of low cell surface receptor expression.

Exome sequencing data failed to account for the discrepancy between functional data and expression on the cell lines that do not respond to calcitonin(s) with no deleterious non-synonymous polymorphisms detected, suggesting that other factors may be at play, such as alternative splicing or rapid constitutive receptor internalisation.

Conclusions

This study shows that GPCR signaling can display significant variation depending on cellular system used, and effects seen in model recombinant cell lines or tumour cell lines are not always reproduced in a more physiologically relevant system and vice versa.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5369-y) contains supplementary material, which is available to authorized users.

Genetically encoded photocross-linkers determine the biological binding site of exendin-4 peptide in the N-terminal domain of the intact human glucagon-like peptide-1 receptor (GLP-1R)

The glucagon-like peptide-1 receptor (GLP-1R) is a key therapeutic target in the management of type II diabetes mellitus, with actions including regulation of insulin biosynthesis and secretion, promotion of satiety, and preservation of β-cell mass. Like most class B G protein-coupled receptors (GPCRs), there is limited knowledge linking biological activity of the GLP-1R with the molecular structure of an intact, full-length, and functional receptor·ligand complex. In this study, we have utilized genetic code expansion to site-specifically incorporate the photoactive amino acid p-azido-l-phenylalanine (azF) into N-terminal residues of a full-length functional human GLP-1R in mammalian cells. UV-mediated photolysis of azF was then carried out to induce targeted photocross-linking to determine the proximity of the azido group in the mutant receptor with the peptide exendin-4. Cross-linking data were compared directly with the crystal structure of the isolated N-terminal extracellular domain of the GLP-1R in complex with exendin(9-39), revealing both similarities as well as distinct differences in the mode of interaction. Generation of a molecular model to accommodate the photocross-linking constraints highlights the potential influence of environmental conditions on the conformation of the receptor·peptide complex, including folding dynamics of the peptide and formation of dimeric and higher order oligomeric receptor multimers. These data demonstrate that crystal structures of isolated receptor regions may not give a complete reflection of peptide/receptor interactions and should be combined with additional experimental constraints to reveal peptide/receptor interactions occurring in the dynamic, native, and full-length receptor state.

A nuclear transport inhibitor that modulates the unfolded protein response and provides in vivo protection against lethal dengue virus infection

BACKGROUND

Dengue virus (DENV) is estimated to cause 390 million infections each year, but there is no licensed vaccine or therapeutic currently available.

METHODS

We describe a novel, high-throughput screen to identify compounds inhibiting the interaction between DENV nonstructural protein 5 and host nuclear transport proteins. We document the antiviral properties of a lead compound against all 4 serotypes of DENV, antibody-dependent enhanced (ADE) infection, and ex vivo and in vivo DENV infections. In addition, we use quantitative reverse-transcription polymerase chain reaction to examine cellular effects upon compound addition.

RESULTS

We identify N-(4-hydroxyphenyl) retinamide (4-HPR) as effective in protecting against DENV-1-4 and DENV-1 ADE infections, with 50% effective concentrations in the low micromolar range. 4-HPR but not the closely related N-(4-methoxyphenyl) retinamide (4-MPR) could reduce viral RNA levels and titers when applied to an established infection. 4-HPR but not 4-MPR was found to specifically upregulate the protein kinase R-like endoplasmic reticulum kinase arm of the unfolded protein response. Strikingly, 4-HPR but not 4-MPR restricted infection in peripheral blood mononuclear cells and in a lethal ADE-infection mouse model.

CONCLUSIONS

4-HPR is a novel antiviral that modulates the unfolded protein response, effective against DENV1-4 at concentrations achievable in the plasma in a clinical setting, and provides protection in a lethal mouse model.

Privileging place: Reflections on involving people with dementia in a residency

Although attention is paid to involving people with dementia as collaborators in research, the issue of place - where involvement actually occurs - has been neglected. This is significant because we know from the academic literature that places can adversely affect social relations and a person's ability to participate as equal partners. This paper privileges place and documents our experiences of running residencies in the English Lake District with people with dementia - Houston, Gardiner and Wallace all have some form of dementia. In doing so we provide a model to reference for involving people with dementia in research and knowledge production, while simultaneously strengthening the evidence base for the residency as a method for participatory research. People with dementia participated in two residencies to co-produce a touring exhibition and educational resource as part of a research dissemination project. We found that by privileging place a more equitable, productive, healthier, and respectful way of involving people with dementia as collaborators in research dissemination could be realised. The project has wider implications for the involvement of people with dementia in not only research, but also public consultations, service evaluations, and policy-related work.

[When is a doctor a good doctor? An analysis of the contents of statements by representatives of the medical profession ]

BACKGROUND

Several professional bodies have developed influential documents which have tried to describe the essential competences of a good doctor. Such an initiative has not been previously conducted in German-speaking countries. Differences between the published statements point towards the significance of differences in the respective sociocultural setting.

METHODS

The first step was to take advantage of a series of standardized written interviews [including the item "What makes a doctor a good doctor?"], conducted with leading German physicians and published serially in the Deutsche Medizinische Wochenschrift. Responses were qualitatively analysed by three assessors in accordance with Grounded Theory. Text fragmentation and assignment of categories was built successively: it was based on the actual material and repeatedly revised.

RESULTS

261 statements were extracted from a total of 83 interviews. It was possible to assign 249 of them to one of the following nine categories: "knowledge", "empathy" and "patient orientation" and, less frequently "practical competence", "genuineness", "helper", "awareness of limits", "life-long learning" and "cooperation". Results were similar for older and younger physicians, or when comparing representatives of clinical and theoretical disciplines.

CONCLUSIONS

It will be worthwhile to survey and evaluate the opinion of additional members of the medical profession and of patients and others with a stake in the health system--comparing and delineating results from different countries--so that a more comprehensive picture can be drawn of "the good doctor".

Analysis of human Nav1.8 expressed in SH-SY5Y neuroblastoma cells

The tetrodotoxin-resistant voltage-gated sodium channel alpha-subunit Nav1.8 is expressed in nociceptors and has been implicated in chronic pain. Difficulties of heterologous expression have so far precluded analysis of the pharmacological properties of human Nav1.8. To address this we have introduced human Nav1.8 in neuroblastoma SH-SY5Y cells. Voltage-clamp analysis showed that human Nav1.8 generated an inward tetrodotoxin-resistant sodium current with an activating threshold around -50 mV, half maximal activation at -11+/-3 mV and a reversal potential of 67+/-4 mV. These properties closely match those of the endogenous rat tetrodotoxin-resistant sodium current in dorsal root ganglia suggesting that the expressed human channel is in a near physiological conformation. Human Nav1.8 was resistant to tetrodotoxin and activated by the pyrethroid toxin deltamethrin. Both voltage-activated and deltamethrin-activated human Nav1.8 were inhibited by the sodium channel blockers BIII 890 CL, NW-1029, and mexiletine. Inhibition of Nav1.8 by these compounds may underlie their known analgesic effects in animal models.

Heterologous expression and functional analysis of rat NaV1.8 (SNS) voltage-gated sodium channels in the dorsal root ganglion neuroblastoma cell line ND7–23

The voltage-gated sodium channel NaV1.8 (SNS, PN3) is thought to be a molecular correlate of the dorsal root ganglion (DRG) tetrodotoxin resistant (TTX-R) Na+ current. TTX-R/NaV1.8 is an attractive therapeutic drug target for inflammatory and neuropathic pain on the basis of its specific distribution in sensory neurones and its modulation by inflammatory mediators. However, detailed analysis of recombinant NaV1.8 has been hampered by difficulties in stably expressing the functional protein in mammalian cells. Here, we show stable expression and functional analysis of rat NaV1.8 (rNaV1.8) in the rat DRG/mouse N18Tg2 neuroblastoma hybridoma cell line ND7-23. Rat NaV1.8 Na+ currents were recorded (789 +/- 89 pA, n=62, over 20-cell passages) that qualitatively resembled DRG TTX-R in terms of gating kinetics and voltage-dependence of activation and inactivation. The local anaesthetic drug tetracaine produced tonic inhibition of rNaV1.8 (mean IC50 value 12.5 microM) and in repeated gating paradigms (2-10 Hz) also showed frequency-dependent block. There was a correlation between the ability of several analogues of the anticonvulsant/analgesic compound lamotrigine to inhibit TTX-R and rNaV1.8 (r=0.72, P<0.001). RT-PCR analysis of wild type ND7-23 cells revealed endogenous expression of the beta1 and beta3 accessory Na+ channel subunits-the possibility that the presence of these subunits assists and stabilises expression of rNaV1.8 is discussed. We conclude that the neuroblastoma ND7-23 cell line is a suitable heterologous expression system for rNaV1.8 Na+ channels in that it allows stable expression of a channel with biophysical properties that closely resemble the native TTX-R currents in DRG neurones. This reagent will prove useful in the search for pharmacological inhibitors of rNaV1.8 as novel analgesics.

The art of perception: from the life world to the medical gaze and back again

Perceptions are often merely regarded as the basic elements of knowledge. They have, however, a complex structure of their own and are far from being elementary. My paper will analyze two basic patterns of perception and some of the resulting medical implications. Most basically, all object perception is characterized by a mixture of knowledge and ignorance (Husserl). Perception essentially perceives with inner and outer horizons, brought about by the kinesthetic activity of the perceiving subject (Sartre). This first layer of perceptual reality, the world of "open" perceptions, is the inescapable background for "every rationality, every value, every existence" (Merleau-Ponty). On an epistemological level a characteristic change of perceptual patterns in medicine was introduced by pathological anatomy (Foucault). The reference of medical perception to the dead body created the new possibility of "absolute" perception, allowing for more precise medical interventions, but at the same time coming into conflict with the open structures of "ordinary," non-scientific perception patterns in everyday life. On the basis of these distinctions, an analysis of the different perceptual patterns in medicine becomes possible. Such an analysis would be the task of a sub-field in medical philosophy that could be called "medical aesthetics" having as its goal an "art of perception" understood as a technique of adequately applying different perceptual patterns in medical practice.

Codes and morals: is there a missing link? (The Nuremberg Code revisited)

Codes are a well known and popular but weak form of ethical regulation in medical practice. There is, however, a lack of research on the relations between moral judgments and ethical Codes, or on the possibility of morally justifying these Codes. Our analysis begins by showing, given the Nuremberg Code, how a typical reference to natural law has historically served as moral justification. We then indicate, following the analyses of H. T. Engelhardt, Jr., and A. MacIntyre, why such general moral justifications of codes must necessarily fail in a society of "moral strangers." Going beyond Engelhardt we argue, that after the genealogical suspicion in morals raised by Nietzsche, not even Engelhardt's "principle of permission" can be rationally justified in a strong sense--a problem of transcendental argumentation in morals already realized by I. Kant. Therefore, we propose to abandon the project of providing general justifications for moral judgements and to replace it with a hermeneutical analysis of ethical meanings in real-world situations, starting with the archetypal ethical situation, the encounter with the Other (E. Levinas).