The basal (ligand-independent) kinase activity of receptor tyrosine kinases (RTKs) promotes trans-phosphorylation on activation loop tyrosines upon ligand-induced receptor dimerization, thus ...upregulating intrinsic kinase activity and triggering intracellular signaling. To understand the molecular determinants of intrinsic kinase activity, we used X-ray crystallography and NMR spectroscopy to analyze pathogenic FGF receptor mutants with gradations in gain-of-function activity. These structural analyses revealed a “two-state” dynamic equilibrium model whereby the kinase toggles between an “inhibited,” structurally rigid ground state and a more dynamic and heterogeneous active state. The pathogenic mutations have different abilities to shift this equilibrium toward the active state. The increase in the fractional population of FGF receptors in the active state correlates with the degree of gain-of-function activity and clinical severity. Our data demonstrate that the fractional population of RTKs in the active state determines intrinsic kinase activity and underscore how a slight increase in the active population of kinases can have grave consequences for human health.
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•FGFRs dynamically exchange between a ground- and active-state conformation•Pathogenic mutations differentially shift the equilibrium toward the active state•Fractional population of RTKs in active state determines intrinsic kinase activity
Basal intrinsic kinase activity of RTKs is necessary to jump-start trans-phosphorylation on A loop tyrosines and thereby upregulate activity. What underlies basal intrinsic kinase activity is, however, unclear. Mohammadi and colleagues studied naturally occurring mutations in FGF receptor kinases, which allowed them to uncover a model whereby kinase molecules move between two conformational states. The authors demonstrate that the fractional population of RTKs in the active state determines basal kinase activity.
Agonists of the vanilloid receptor transient vanilloid potential 1 (TRPV1) are emerging as highly efficacious nonopioid analgesics in preclinical studies. These drugs selectively lesion TRPV1+ ...primary sensory afferents, which are responsible for the transmission of many noxious stimulus modalities. Resiniferatoxin (RTX) is a very potent and selective TRPV1 agonist and is a promising candidate for treating many types of pain. Recent work establishing intrathecal application of RTX for the treatment of pain resulting from advanced cancer has demonstrated profound analgesia in client-owned dogs with osteosarcoma. The present study uses transcriptomics and histochemistry to examine the molecular mechanism of RTX action in rats, in clinical canine subjects, and in 1 human subject with advanced cancer treated for pain using intrathecal RTX. In all 3 species, we observe a strong analgesic action, yet this was accompanied by limited transcriptional alterations at the level of the dorsal root ganglion. Functional and neuroanatomical studies demonstrated that intrathecal RTX largely spares susceptible neuronal perikarya, which remain active peripherally but unable to transmit signals to the spinal cord. The results demonstrate that central chemo-axotomy of the TRPV1+ afferents underlies RTX analgesia and refine the neurobiology underlying effective clinical use of TRPV1 agonists for pain control.
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•Self-assembly in model DPPC lipids and NaDC bile salt by SANS and DLS experiments.•Bile salt creates structural interference against cohesive tendency of DPPC bilayers.•NaDC steric ...interactions cause transition toward different supramolecular structures.
Small angle neutron scattering (SANS) and dynamic light scattering (DLS) were used to study different aggregation states in sodium deoxycholate (NaDC)-phosphatidylcholine systems at T=60°C. Size and shape of the aggregates investigated as a function of the NaDC bile salt concentration (at the constant DPPC concentration of 6mM) indicate a strong dependence of the size and morphology of the generated aggregates on the relative amount of NaDC bile salt. More specifically large occupied area of the bile salt induces a steric interaction which promotes the transition toward a variety of supramolecular structures ranging from ellipsoidal vesicles, ribbon-like structures, up to final spherical mixed micelles at the large amount of bile salt of 10mM NaDC. The findings of the obtained results give important insight for understanding the formation of different topologies in aqueous lipid–bile salt mixtures as well as stimulate new routes for liposome reconstitution–solubilisation processes suitable for technological applications.
Terrestrial gamma ray flashes (TGFs) are beams of high‐energy photons associated to lightning. These photons are the bremsstrahlung of energetic electrons whose origin is currently explained by two ...mechanisms: energizing electrons in weak, but large‐scale thundercloud fields or the acceleration of low‐energy electrons in strong, but localized fields of lightning leaders. Contemporary measurements by the Atmosphere‐Space Interactions Monitor suggest that the production of TGFs is related to the leader step and associated streamer coronae when upward moving intracloud lightning illuminates. Based on these observations, we apply a particle‐in‐cell Monte Carlo code tracing electrons in the superposed electric field of two encountering streamer coronae and modeling the subsequent photon emission. We also perform a parameter study by solving the deterministic equations of motion for one electron. We find that this mechanism can explain the occurrence of TGFs with photons energies of several MeV lasting for tens to hundreds of μs, in agreement with observations.
Plain Language Summary
For more than two decades, it has been known that thunderstorms emit high‐energy X‐rays and γ rays, the so‐called terrestrial gamma ray flashes (TGFs) lasting for tens to hundreds of μs, which are the bremsstrahlung (“braking radiation”) of energetic electrons and are the most energetic natural phenomena on Earth. Within the last years, two theories have been crystallized out to explain the origin of energetic electrons: the acceleration and multiplication of energetic electrons as remnants of cosmic rays in the large‐scale electric fields of thunderclouds or the acceleration of thermal electrons in high electric fields in the vicinity of the tips of lightning leaders. Contemporary measurements of the Atmosphere‐Space Interactions Monitor (ASIM) show that TGFs are produced at the onset of the main optical lightning pulse, indicating that the electron acceleration is related to the upward pointing lighting leader tip. We have performed computational simulations of the electron acceleration in the superposed electric field of two encountering streamer coronae, a compilation of small plasma channels with high‐field tips, arising in the proximity of the lightning leader tip and the upper charge layer. We find that this scenario can explain the occurrence of TGFs with energies and durations compatible with previous and contemporary measurements.
Key Points
Relativistic electrons are produced during the breakdown of ICs during a current surge when two streamer coronae approach each other
The acceleration of electrons between two streamer coronae leads to TGFs lasting for tens to hundreds of μs with photon energies of
O(10 MeV)
The maximum photon energy in TGFs is determined by the electric field of the upper cloud charge layer
Verification of candidate biomarkers relies upon specific, quantitative assays optimized for selective detection of target proteins, and is increasingly viewed as a critical step in the discovery ...pipeline that bridges unbiased biomarker discovery to preclinical validation. Although individual laboratories have demonstrated that multiple reaction monitoring (MRM) coupled with isotope dilution mass spectrometry can quantify candidate protein biomarkers in plasma, reproducibility and transferability of these assays between laboratories have not been demonstrated. We describe a multilaboratory study to assess reproducibility, recovery, linear dynamic range and limits of detection and quantification of multiplexed, MRM-based assays, conducted by NCI-CPTAC. Using common materials and standardized protocols, we demonstrate that these assays can be highly reproducible within and across laboratories and instrument platforms, and are sensitive to low mug/ml protein concentrations in unfractionated plasma. We provide data and benchmarks against which individual laboratories can compare their performance and evaluate new technologies for biomarker verification in plasma.
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