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Touchard A, Mendel HC, Boulogne I, Herzig V, Braga Emidio N, King GF, Triquigneaux M, Jaquillard L, Beroud R, De Waard M, Delalande O, Dejean A, Muttenthaler M, Duplais C. Heterodimeric Insecticidal Peptide Provides New Insights into the Molecular and Functional Diversity of Ant Venoms. ACS Pharmacol Transl Sci 2020; 3:1211-1224. [PMID: 33344898 DOI: 10.1021/acsptsci.0c00119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Indexed: 12/14/2022]
Abstract
Ants use venom for predation, defense, and communication; however, the molecular diversity, function, and potential applications of ant venom remains understudied compared to other venomous lineages such as arachnids, snakes and cone snails. In this work, we used a multidisciplinary approach that encompassed field work, proteomics, sequencing, chemical synthesis, structural analysis, molecular modeling, stability studies, and in vitro and in vivo bioassays to investigate the molecular diversity of the venom of the Amazonian Pseudomyrmex penetrator ants. We isolated a potent insecticidal heterodimeric peptide Δ-pseudomyrmecitoxin-Pp1a (Δ-PSDTX-Pp1a) composed of a 27-residue long A-chain and a 33-residue long B-chain cross-linked by two disulfide bonds in an antiparallel orientation. We chemically synthesized Δ-PSDTX-Pp1a, its corresponding parallel AA and BB homodimers, and its monomeric chains and demonstrated that Δ-PSDTX-Pp1a had the most potent insecticidal effects in blowfly assays (LD50 = 3 nmol/g). Molecular modeling and circular dichroism studies revealed strong α-helical features, indicating its cytotoxic effects could derive from cell membrane pore formation or disruption. The native heterodimer was substantially more stable against proteolytic degradation (t 1/2 = 13 h) than its homodimers or monomers (t 1/2 < 20 min), indicating an evolutionary advantage of the more complex structure. The proteomic analysis of Pseudomyrmex penetrator venom and in-depth characterization of Δ-PSDTX-Pp1a provide novel insights in the structural complexity of ant venom and further exemplifies how nature exploits disulfide-bond formation and dimerization to gain an evolutionary advantage via improved stability, a concept that is highly relevant for the design and development of peptide therapeutics, molecular probes, and bioinsecticides.
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Affiliation(s)
- Axel Touchard
- CNRS, UMR Ecofog, AgroParisTech, Cirad, INRAE, Université des Antilles, Université de Guyane, Kourou 97310, France
| | - Helen C Mendel
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Isabelle Boulogne
- Université de ROUEN, UFR des Sciences et Techniques, Laboratoire Glycobiologie et Matrice Extracellulaire Végétale, UPRES-EA 4358, Fédération de Recherche Normandie Végétal FED 4277, Mont-Saint-Aignan 76821, France
| | - Volker Herzig
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.,GeneCology Research Centre, School of Science, Technology and Engineering, University of the Sunshine Coast, Sippy Downs, Queensland 4556, Australia
| | - Nayara Braga Emidio
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | | | - Lucie Jaquillard
- Smartox Biotechnology, 6 rue des Platanes, Saint Egrève 38120, France
| | - Rémy Beroud
- Smartox Biotechnology, 6 rue des Platanes, Saint Egrève 38120, France
| | - Michel De Waard
- Smartox Biotechnology, 6 rue des Platanes, Saint Egrève 38120, France.,Université de Nantes, CNRS, INSERM, L'institut du thorax, Nantes 44000, France.,LabEx, Ion Channels, Science & Therapeutics, Valbonne 06560, France
| | - Olivier Delalande
- Institute of Genetics and Development of Rennes (IGDR), CNRS UMR 6290, Université de Rennes Faculté de Pharmacie, 2 avenue du Professeur Léon Bernard, Rennes 35043, France
| | - Alain Dejean
- CNRS, UMR Ecofog, AgroParisTech, Cirad, INRAE, Université des Antilles, Université de Guyane, Kourou 97310, France.,Ecolab, Université de Toulouse, CNRS, INPT, UPS, Toulouse 31058, France
| | - Markus Muttenthaler
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.,Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, Vienna 1090, Austria
| | - Christophe Duplais
- CNRS, UMR Ecofog, AgroParisTech, Cirad, INRAE, Université des Antilles, Université de Guyane, Kourou 97310, France
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Horvath L, Bodmer D, Radojevic V, Monge Naldi A. Activin Signaling Disruption in the Cochlea Does Not Influence Hearing in Adult Mice. Audiol Neurootol 2014; 20:51-61. [DOI: 10.1159/000366152] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 07/24/2014] [Indexed: 11/19/2022] Open
Abstract
Activin, a member of the TGF-F superfamily, was found to play an important role in the development, repair and apoptosis of different tissues and organs. Accordingly, activin signaling is involved in the development of the cochlea. Activin binds to its receptor ActRII, then dimerizes with ActRI and induces a signaling pathway resulting in gene expression. A study reported a case of fibrodysplasia ossificans progressiva with an unusual mutation in the ActRI gene leading to sensorineural hearing loss. This draws attention to the role of activin and its receptors in the developed cochlea. To date, only the expression of ActRII is known in the adult mammalian cochlea. In this study, we present for the first time the presence of activin A and ActRIB in the adult cochlea. Transgenic mice with postnatal dominant-negative ActRIB expression causing disruption of activin signaling in vivo were used for assessing cochlear morphology and hearing ability through the auditory brainstem response (ABR) threshold. Nonfunctioning ActRIB did not affect the ABR thresholds and did not alter the microscopic anatomy of the cochlea. We conclude, therefore, that activin signaling is not necessary for hearing in adult mice under physiological conditions but may be important during and after damaging events in the inner ear. i 2014 S. Karger AG, Basel
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Farahbakhsh NA, Narins PM. Slow motility in hair cells of the frog amphibian papilla: myosin light chain-mediated shape change. Hear Res 2008; 241:7-17. [PMID: 18534795 PMCID: PMC2516351 DOI: 10.1016/j.heares.2008.04.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2007] [Revised: 04/10/2008] [Accepted: 04/14/2008] [Indexed: 12/01/2022]
Abstract
Using video, fluorescence and confocal microscopy, quantitative analysis and modeling, we investigated intracellular processes mediating the calcium/calmodulin (Ca(2+)/CaM)-dependent slow motility in hair cells dissociated from the rostral region of amphibian papilla, one of the two auditory organs in frogs. The time course of shape changes in these hair cells during the period of pretreatment with several specific inhibitors, as well as their response to the calcium ionophore, ionomycin, were recorded and compared. These cells respond to ionomycin with a tri-phasic shape change: an initial phase of iso-volumetric length decrease; a period of concurrent shortening and swelling; and the final phase of increase in both length and volume. We found that both the myosin light chain kinase inhibitor, ML-7, and antagonists of the multifunctional Ca(2+)/CaM-dependent kinases, KN-62 and KN-93, inhibit the iso-volumetric shortening phase of the response to ionomycin. The type 1 protein phosphatase inhibitors, calyculin A and okadaic acid induce minor shortening on their own, but do not significantly alter phase 1 response. However, they appear to counter effects of the inhibitors of Ca(2+)/CaM-dependent kinases. We hypothesize that an active actomyosin-based process mediates the iso-volumetric shortening in the frog rostral amphibian papillar hair cells.
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Affiliation(s)
- Nasser A Farahbakhsh
- Department of Physiological Science, 621 Charles E. Young Drive S., University of California, Los Angeles, CA 90095-1606, USA.
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Borkó R, Batta TJ, Sziklai I. Slow motility, electromotility and lateral wall stiffness in the isolated outer hair cells. Hear Res 2005; 207:68-75. [PMID: 15950414 DOI: 10.1016/j.heares.2005.04.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2005] [Revised: 04/05/2005] [Accepted: 04/08/2005] [Indexed: 11/18/2022]
Abstract
Slow motile length changes of isolated, apical turn outer hair cells (OHCs) (n=36) were induced by perfusion of saline (flow rate: 0.6 microl/min) as a mechanical challenge or by perfusion of 12.5 mM KCl solution for 90 s as a chemical and mechanical challenge with and without ocadaic acid (OA), a serine/threonine protein phosphatase inhibitor. Electromotility was evoked by square pulses from +/-35 mV to +/-240 mV during the slow shortening and recovery period (n=36). Stiffness of the lateral wall was measured by the micropipette aspiration technique (n=20). Saline perfusion caused a reversible shortening of 774+/-87 nm (n=9) as well as K+ of 1465+/-159 nm (n=9). Slow shortening increased lateral wall stiffness (1.25+/-0.02 to 1.52+/-0.03 nN/microm) (n=5-5). Simultaneously, electromotility magnitude decreased (n=9). Ocadaic acid blocked slow shortening, increased lateral wall stiffness, and decreased the magnitude of electromotility. Mechanical or mechanical+chemical stimulation of ocadaic acid treated OHCs do not further change stiffness or electromotility. Isolated OHCs respond with slow shortening and consutive cell stiffness increase to mechanical insult. This phenomenon seems operating with calcium-, and phosphorylation-dependent modifications of the cytoskeletal proteins. The subsequent electromotility gain decrease suggests a slow OHC shortening driven regulation of the cochlear amplifier with simultaneous safety control of the auditory periphery against overstimulation.
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Affiliation(s)
- Rezsö Borkó
- ORL Clinic, University of Debrecen, Health Science Center, Nagyerdei krt. 98, 4012 Debrecen, Hungary
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Batta TJ, Panyi G, Gáspár R, Sziklai I. Active and passive behaviour in the regulation of stiffness of the lateral wall in outer hair cells of the guinea-pig. Pflugers Arch 2003; 447:328-36. [PMID: 14586657 DOI: 10.1007/s00424-003-1186-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2003] [Revised: 08/18/2003] [Accepted: 09/09/2003] [Indexed: 10/26/2022]
Abstract
The stiffness of the outer hair cell (OHC) lateral wall, measured by the micropipette aspiration technique, is non-linear, decreasing from the ciliary pole (stiffness parameter Sp 1.83+/-0.13 nN/microm n=10) towards the cell base (Sp 1.14+/-0.16 nN/microm, n=10) irrespective of the cochleoapical or cochleobasal origin of the cells. The length of the aspirated lateral wall segment was related exponentially to the duration of the applied negative pressure (6 cm H2O) in the synaptic region of the OHCs whereas an active, sigmoid component was observed between 30 and 60 s in the supranuclear regions. A significant increase of the midlateral wall stiffness (to 1.91+/-0.23 nN/microm; n=10) was observed in calcium-free medium and the sigmoid component of the response of the lateral wall was abolished. Salicylate (5 mM) had no significant effect on the active sigmoid behaviour of the lateral wall (n=10). Gadolinium (5 mM), a non-specific cation channel blocker, increased the stiffness of the lateral wall and attenuated the active component (n=10). The motor protein prestin thus does not seem to be involved in the active stiffness regulation seen in this study. A role for the cortical cytoskeleton in the regulation of stiffness seems reasonable according to our model. The mechanism may involve calcium-dependent metabolic modification of cytoskeletal or membrane proteins.
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Affiliation(s)
- Tamás József Batta
- ORL Clinic, Medical and Health Science Centre, University of Debrecen, Nagyerdei krt. 98., 4012 Debrecen, Hungary
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Farkas Z, Sziklai I. Potassium-induced slow motility is partially calcium-dependent in isolated outer hair cells. Acta Otolaryngol 2003; 123:160-3. [PMID: 12701732 DOI: 10.1080/0036554021000028127] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Low flow rate (0.6 microl/min) administration of high concentration potassium solutions (12.5, 25 and 37.5 mM) was tested for evoking slow-motility length changes in isolated, apical turn, guinea pig outer hair cells (OHCs) (length 65-80 microm; n = 38). Control OHCs (n = 16) showed a flow rate-dependent, reversible, longitudinal shortening of 0.5-3 microm during perfusion with normal saline. Potassium, an effective depolarizing agent for OHCs, induced a concentration-dependent cell shortening of 0.5-13 microm. These cell shape changes were reversible. The magnitude of shortening was significantly (p < 0.01) decreased in a calcium-free incubation medium (n = 8). The velocity of the shortening was 300 nm/s in the first 10 s after application of 37.5 mM K+ in a normal incubation medium and decreased to 100 nm/s during the next 10 s. Corresponding velocities in calcium-free solutions were 100 and 50 nm/s, respectively. K+-induced shortening velocities were not significantly different from control values after 30 s. It appears that K+-induced OHC shortening is sensitive to the calcium content of the incubation medium during the first 10 s. Higher flow rate (1.5 microl/min) administration of K+ makes the velocity and magnitude of slow motility of OHCs insensitive to the absence of calcium. These results highlight the fact that one of the critical technical points in fluid perfusion experiments with isolated OHCs is selecting a safe low flow rate of < 0.6 microl/min. At this perfusion rate, K+-induced OHC shortening is composed of both calcium-sensitive and -insensitive components.
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Affiliation(s)
- Zsolt Farkas
- Clinic of Otorhinolaryngology and Head & Neck Surgery, Debrecen University, Debrecen, Hungary
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Kawasaki E, Hattori N, Miyamoto E, Yamashita T, Inagaki C. mRNA expression of kidney-specific ClC-K1 chloride channel in single-cell reverse transcription-polymerase chain reaction analysis of outer hair cells of rat cochlea. Neurosci Lett 2000; 290:76-8. [PMID: 10925178 DOI: 10.1016/s0304-3940(00)01310-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Outer hair cells (OHCs) of cochlea have been suggested to have Cl(-) channels sensitive to an ototoxic diuretic, furosemide. We therefore examined whether kidney-specific chloride channels (ClC-K1 and ClC-K2) and ClC-5 are also expressed in OHCs of rat cochlea, assuming that these channels might be the targets of oto-nephrotoxic drugs, by single-cell reverse transcription-polymerase chain reaction (RT-PCR) technique. Single-cell RT-PCR revealed the presence of transcripts of ClC-K1 in OHCs which was verified by DNA sequencing, while ClC-K2 and ClC-5 were not detected. The possible roles of ClC-K1 in OHCs are discussed.
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Affiliation(s)
- E Kawasaki
- Department of Pharmacology, Kansai Medical University, Fumizono-cho 10-15, Moriguchi-shi, 570-8506, Osaka, Japan
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Sansom SC, Ma R, Carmines PK, Hall DA. Regulation of Ca(2+)-activated K(+) channels by multifunctional Ca(2+)/calmodulin-dependent protein kinase. Am J Physiol Renal Physiol 2000; 279:F283-8. [PMID: 10919847 DOI: 10.1152/ajprenal.2000.279.2.f283] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of mesangial cells by ANG II provokes release of intracellular Ca(2+) stores and subsequent Ca(2+) influx through voltage-gated channels, events that are reflected by a large transient increase in intracellular concentration [Ca(2+)](i) followed by a modest sustained elevation in [Ca(2+)](i). These ANG II-induced alterations in [Ca(2+)](i) elicit activation of large Ca(2+)-activated K(+) channels (BK(Ca)) in a negative-feedback manner. The mechanism of this BK(Ca) feedback response may involve the direct effect of intracellular Ca(2+) on the channel and/or channel activation by regulatory enzymes. The present study utilized patch-clamp and fura 2 fluorescence techniques to assess the involvement of multifunctional calcium calmodulin kinase II (CAMKII) in the BK(Ca) feedback response. In cell-attached patches, KN62 (specific inhibitor of CAMKII) either abolished or reduced to near zero the ANG II-induced BK(Ca) feedback response. This phenomenon did not reflect direct effects of KN62 on the BK(Ca) channel, because this agent alone did not significantly alter BK(Ca) channel activity in inside-out patches. KN62 also failed to alter either the transient peak or sustained plateau phases of the [Ca(2+)](i) response to ANG II. In inside-out patches (1 microM Ca(2+) in bath), calmodulin plus ATP activated BK(Ca) channels in the presence but not the absence of CAMKII. These observations are consistent with the postulate that CAMKII is involved in the BK(Ca) feedback response of mesangial cells, acting to potentiate the influence of increased [Ca(2+)](i) on the BK(Ca) channel or a closely associated regulator of the channel. An additional effect of CAMKII to activate a voltage-gated Ca(2+) channel cannot be ruled out by these experiments.
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Affiliation(s)
- S C Sansom
- Department of Physiology and Biophysics, University of Nebraska Medical Center, Omaha 68198-4575, USA.
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Kawasaki E, Hattori N, Miyamoto E, Yamashita T, Inagaki C. Single-cell RT-PCR demonstrates expression of voltage-dependent chloride channels (ClC-1, ClC-2 and ClC-3) in outer hair cells of rat cochlea. Brain Res 1999; 838:166-70. [PMID: 10446329 DOI: 10.1016/s0006-8993(99)01730-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We investigated whether voltage-dependent chloride channels (ClC-1, ClC-2 and ClC-3) are expressed in outer hair cells (OHCs) of rat cochlea using a single-cell reverse transcription-polymerase chain reaction (RT-PCR) technique. The OHCs were isolated from rat cochlea and the cytoplasm of each OHC was suctioned into a glass pipette containing RT-PCR reaction buffer with RNase inhibitor. RT-PCR revealed the presence of transcripts of ClC-1, ClC-2 and ClC-3, which were verified by DNA sequencing. The possible roles of these chloride channels in OHCs are discussed.
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Affiliation(s)
- E Kawasaki
- Department of Pharmacology, Kansai Medical University, Fumizono-cho 10-15, Moriguchi, Osaka 570-8506, Japan
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