DD04107-Derived neuronal exocytosis inhibitor peptides: Evidences for synaptotagmin-1 as a putative target

The analgesic peptide DD04107 (Pal-EEMQRR-NH2) and its acetylated analogue inhibit a-calcitonin gene-related peptide (a-CGRP) exocytotic release from primary sensory neurons. Examining the crystal structure of the SNARE-Synaptotagmin-1(Syt1) complex, we hypothesized that these peptides could inhibit neuronal exocytosis by binding to Syt1, hampering at least partially its interaction with the SNARE complex. To address this hypothesis, we first interrogate the role of individual side-chains on the inhibition of a-CGRP release, finding that E1, M3, Q4 and R6 residues were crucial for activity. CD and NMR conformational analysis showed that linear peptides have tendency to adopt a-helical conformations, but the results with cyclic analogues indicated that this secondary structure is not needed for activity. Isothermal titration calorimetry (ITC) measurements demonstrate a direct interaction of some of these peptides with Syt1-C2B domain, but not with Syt7-C2B region, indicating selectivity. As expected for a compound able to inhibit a-CGRP release, cyclic peptide derivative Pal-E-cyclo[EMQK]R-NH2 showed potent in vivo analgesic activity, in a model of inflammatory pain. Molecular dynamics simulations provided a model consistent with KD values for the interaction of peptides with Syt1-C2B domain, and with their biological activity. Altogether, these results identify Syt1 as a potential new analgesic target. © 202

The structure and flexibility analysis of the Arabidopsis synaptotagmin 1 reveal the basis of its regulation at membrane contact sites

17 pags., 7 figs., 1 tab.Non-vesicular lipid transfer at ER and plasma membrane (PM) contact sites (CS) is crucial for the maintenance of membrane lipid homeostasis. Extended synaptotagmins (E-Syts) play a central role in this process as they act as molecular tethers of ER and PM and as lipid transfer proteins between these organelles. E-Syts are proteins constitutively anchored to the ER through an N-terminal hydrophobic segment and bind the PM via a variable number of C-terminal C2 domains. Synaptotagmins (SYTs) are the plant orthologous of E-Syts and regulate the ER–PM communication in response to abiotic stress. Combining different structural and biochemical techniques, we demonstrate that the binding of SYT1 to lipids occurs through a Ca2+-dependent lipid-binding site and by a site for phosphorylated forms of phosphatidylinositol, thus integrating two different molecular signals in response to stress. In addition, we show that SYT1 displays three highly flexible hinge points that provide conformational freedom to facilitate lipid extraction, protein loading, and subsequent transfer between PM and ER.This work was funded by grants from Agencia Estatal de Investigación (AEI, Spain) and Fondo Europeo de Desarrollo Regional (European Union) (BIO2017-89523-R to A Albert). A Albert and D Siliqi thank ALBA (beamline XALOC) and Diamond Light Source (beamline B21, proposal MX21741) for granting access to the synchrotron radiation source. We thank Nathan Cowieson and Charlotte JC Edwards-Gayle from Diamond Light Source for their assistance in the preparation of the SAXS experimentsPeer reviewe

Pneumococcal phosphorylcholine esterase, Pce, contains a metal binuclear center that is essential for substrate binding and catalysis

The phosphorylcholine esterase from Streptococcus pneumoniae, Pce, catalyzes the hydrolysis of phosphorylcholine residues from teichoic and lipoteichoic acids attached to the bacterial envelope and comprises a globular N-terminal catalytic module containing a zinc binuclear center and an elongated C-terminal choline-binding module. The dependence of Pce activity on the metal/enzyme stoichiometry shows that the two equivalents of zinc are essential for the catalysis, and stabilize the catalytic module through a complex metal-ligand coordination network. The pH dependence of Pce activity toward the alternative substrate p-nitrophenylphosphorylcholine (NPPC) shows that kcat and kcat/Km depend on the protonation state of two protein residues that can be tentatively assigned to the ionization of the metal-bound water (hydrogen bonded to D89) and to H228. Maximum activity requires deprotonation of both groups, although the catalytic efficiency is optimum for the single deprotonated form. The drastic reduction of activity in the H90A mutant, which still binds two Zn2+ ions at neutral pH, indicates that Pce activity also depends on the geometry of the metallic cluster. The denaturation heat capacity profile of Pce exhibits two peaks with Tm values of 39.6°C (choline-binding module) and 60.8°C (catalytic module). The H90A mutation reduces the high-temperature peak by about 10°C. Pce is inhibited in the presence of 1 mM zinc, but this inhibition depends on pH, buffer, and substrate species. A reaction mechanism is proposed on the basis of kinetic data, the structural model of the Pce:NPPC complex, and the currently accepted mechanism for other Zn-metallophosphoesterases

Insights into synaptotagmin-1 C2B domain as a putative target for new analgesic

17th Iberian Peptide Meeting, Madrid, 5-7th February 2020SAF2015-66275-C2-R, CTQ2017-84371-P, RTI2018-097189-C2, CSIC, 201880E109, 201980E030.Peer reviewe

Chemical tolls to modulate kchip3 signaling

Trabajo presentado en el 19th Meeting SEQT, celebrado en Vitoria-Gasteiz (España) del 8 al 11 de julio de 2019.DREAM (Downstream Regulatory Element Antagonist Modulator), also known as KChIP-3 or calsenilin, is a multifunctional calcium binding protein that controls the expression level and/or the activity of several proteins related to calcium homeostasis, neuronal excitability and neuronal survival. As an auxiliary protein in the plasma membrane, DREAM interacts with KV4 potassium channels, L- and T-type voltage-dependent calcium channels, NMDA receptors, presenilins and the transcriptor factor ATF6.1 The interaction between DREAM and KV4 potassium channels regulates of A-type outward potassium currents (IA) that is responsible of the fast repolarization of neuron action potentials and frequency of firing.2 Using a multidisciplinary approach that involves drug design, organic chemistry, surface plasmon resonance assays, electrophysiological recordings of KV4.3/DREAM channels, and IA recordings in rat dorsal root ganglion neurons, we have identified IQM-266.3 IQM-266 slows the inactivation kinetics, and this effect may explain why at concentrations lower than the IC50, IQM-266 augments the efflux of potassium ions resulting in an increase of the charge (activating effect). This effect could be the basis of a promising therapeutic strategy for the treatment of certain neuronal pathologies (epilepsy, Alzheimer disease or ataxia), in which a downregulation of KV4.3 or DREAM has been demonstrated.4 IQM-266 also modulated IA from rat DRG neurons. Overall, IQM-266 constitutes a novel small chemical tool suitable to modulate KV4.3 channels in native systems, that might allow a better understanding of DREAM physiological roles, as well as modulation of neuronal IA current in pathological processes

Crystallization of the pneumococcal autolysin LytC: in-house phasing using novel lanthanide complexes

The complete pneumococcal autolysin LytC has been crystallized by the hanging-drop vapor-diffusion method. A SAD data set has been collected in-house from a Gd derivative up to 2.6 Å resolution

Synthesis and Biophysical and Biological Studies of N-Phenylbenzamide Derivatives Targeting Kinetoplastid Parasites

The AT-rich mitochondrial DNA (kDNA) of trypanosomatid parasites is a target of DNA minor groove binders. We report the synthesis, antiprotozoal screening, and SAR studies of three series of analogues of the known antiprotozoal kDNA binder 2-((4-(4-((4,5-dihydro-1H-imidazol-3-ium-2-yl)amino)benzamido)phenyl)amino)-4,5-dihydro-1H-imidazol-3-ium (1a). Bis(2-aminoimidazolines) (1) and bis(2-aminobenzimidazoles) (2) showed micromolar range activity against Trypanosoma brucei, whereas bisarylimidamides (3) were submicromolar inhibitors of T. brucei, Trypanosoma cruzi, and Leishmania donovani. None of the compounds showed relevant activity against the urogenital, nonkinetoplastid parasite Trichomonas vaginalis. We show that series 1 and 3 bind strongly and selectively to the minor groove of AT DNA, whereas series 2 also binds by intercalation. The measured pKa indicated different ionization states at pH 7.4, which correlated with the DNA binding affinities (ΔTm) for series 2 and 3. Compound 3a, which was active and selective against the three parasites and displayed adequate metabolic stability, is a fine candidate for in vivo studies.Agencia Estatal de InvestigaciónEuropean Regional Development FundRecovery and Resilience Facility, RRF, NextGenerationEUPetroleum Technology Development FundDepto. de Microbiología y ParasitologíaTRUEpubAPC financiada por la UC