Coordination spatio-temporelle des regulateurs du reseau branche d’actine dans les structures motiles

Cell motility is an integrated process involved in critical phenomena such as axonal pathfinding and synaptic plasticity. Dysregulation of cell motility can induce metastasis and abnormal spine shapes observed in neuropsychiatric disorders like autism and schizophrenia. Therefore it is essential to understand how cell motility is regulated. Cell motility requires the formation of branched actin networks propelled by actin polymerization that lead to the formation of membrane protrusions such as the lamellipodium. Several actin regulatory proteins are involved in this process, such as Rac1 and the WAVE and ARP2/3 complexes. Using single protein tracking, we revealed key phenomena concerning the spatio-temporal regulation of lamellipodium formation by actin regulatory proteins. We found that the localization and activation of the WAVE complex was enzymatically regulated, but also mechanically. First, we showed that the Rac1 RhoGTPase activates the WAVE complex specifically at the tip of the lamellipodium. We also showed that WAVE complex localization is regulated by the dynamics of branched-network actin filaments. This study confirms the crucial role of the WAVE complex in lamellipodium formation and reveals the existence of a mechanical regulation of the localization of this complex in the cell.La motilité cellulaire est un processus intégré essentiel à de nombreux phénomènes physiologiques tels que la formation du cône de croissance et la plasticité synaptique. Des dérégulations de la motilité cellulaire peuvent être à l’origine de la formation de métastases ou de pathologies neuropsychiatriques comme la schizophrénie et l'autisme. La compréhension des mécanismes régulant la migration cellulaire est donc un enjeu majeur. La motilité cellulaire repose sur la formation de diverses structures constituées de réseaux d’actine branchés telles que le lamellipode. La formation du lamellipode nécessite l’intervention de protéines régulatrices de l’actine telles que Rac1 et les complexes Wave et Arp2/3. Grâce à l’utilisation de suivi de protéine unique, nous avons pu comprendre comment la coordination spatio-temporelle de ces régulateurs contrôle la formation et la morphologie des lamellipodes de cellules migrantes. Nous avons ainsi découvert que l’activation et la localisation du complexe Wave étaient régulées de manière enzymatique mais également mécanique. Dans une première étude, nous avons montré que la RhoGTPase Rac1 active le complexe Wave spécifiquement à l’extrémité du lamellipode. Dans une seconde étude, nous avons révélé que la localisation du complexe Wave est régulée par la dynamique des filaments des réseaux branchés d’actine. Ces données soulignent l’importance du complexe Wave dans la formation du lamellipode et révèlent l’existence d’une régulation mécanique de la localisation du complexe Wave

Spatio-temporal coordination of branched actin network regulators in motile structures

La motilité cellulaire est un processus intégré essentiel à de nombreux phénomènes physiologiques tels que la formation du cône de croissance et la plasticité synaptique. Des dérégulations de la motilité cellulaire peuvent être à l’origine de la formation de métastases ou de pathologies neuropsychiatriques comme la schizophrénie et l'autisme. La compréhension des mécanismes régulant la migration cellulaire est donc un enjeu majeur. La motilité cellulaire repose sur la formation de diverses structures constituées de réseaux d’actine branchés telles que le lamellipode. La formation du lamellipode nécessite l’intervention de protéines régulatrices de l’actine telles que Rac1 et les complexes Wave et Arp2/3. Grâce à l’utilisation de suivi de protéine unique, nous avons pu comprendre comment la coordination spatio-temporelle de ces régulateurs contrôle la formation et la morphologie des lamellipodes de cellules migrantes. Nous avons ainsi découvert que l’activation et la localisation du complexe Wave étaient régulées de manière enzymatique mais également mécanique. Dans une première étude, nous avons montré que la RhoGTPase Rac1 active le complexe Wave spécifiquement à l’extrémité du lamellipode. Dans une seconde étude, nous avons révélé que la localisation du complexe Wave est régulée par la dynamique des filaments des réseaux branchés d’actine. Ces données soulignent l’importance du complexe Wave dans la formation du lamellipode et révèlent l’existence d’une régulation mécanique de la localisation du complexe Wave.Cell motility is an integrated process involved in critical phenomena such as axonal pathfinding and synaptic plasticity. Dysregulation of cell motility can induce metastasis and abnormal spine shapes observed in neuropsychiatric disorders like autism and schizophrenia. Therefore it is essential to understand how cell motility is regulated. Cell motility requires the formation of branched actin networks propelled by actin polymerization that lead to the formation of membrane protrusions such as the lamellipodium. Several actin regulatory proteins are involved in this process, such as Rac1 and the WAVE and ARP2/3 complexes. Using single protein tracking, we revealed key phenomena concerning the spatio-temporal regulation of lamellipodium formation by actin regulatory proteins. We found that the localization and activation of the WAVE complex was enzymatically regulated, but also mechanically. First, we showed that the Rac1 RhoGTPase activates the WAVE complex specifically at the tip of the lamellipodium. We also showed that WAVE complex localization is regulated by the dynamics of branched-network actin filaments. This study confirms the crucial role of the WAVE complex in lamellipodium formation and reveals the existence of a mechanical regulation of the localization of this complex in the cell

Regulation of the microtubule network; <i>the shaft matters!</i>

In cells, the microtubule network continually assembles and disassembles. The regulation of microtubule growth or shortening has almost exclusively been studied at their dynamic ends. However, microtubules are dynamic all along their entire shaft. A dynamic shaft increases the lifetime and length of a microtubule by reducing the shortening phases and promoting its regrowth. Here, we discuss how shaft dynamics can regulate microtubule network organization, intracellular transport, and polarization of the network

Spatio-temporal coordination of branched actin network regulators in motile structures

La motilité cellulaire est un processus intégré essentiel à de nombreux phénomènes physiologiques tels que la formation du cône de croissance et la plasticité synaptique. Des dérégulations de la motilité cellulaire peuvent être à l’origine de la formation de métastases ou de pathologies neuropsychiatriques comme la schizophrénie et l'autisme. La compréhension des mécanismes régulant la migration cellulaire est donc un enjeu majeur. La motilité cellulaire repose sur la formation de diverses structures constituées de réseaux d’actine branchés telles que le lamellipode. La formation du lamellipode nécessite l’intervention de protéines régulatrices de l’actine telles que Rac1 et les complexes Wave et Arp2/3. Grâce à l’utilisation de suivi de protéine unique, nous avons pu comprendre comment la coordination spatio-temporelle de ces régulateurs contrôle la formation et la morphologie des lamellipodes de cellules migrantes. Nous avons ainsi découvert que l’activation et la localisation du complexe Wave étaient régulées de manière enzymatique mais également mécanique. Dans une première étude, nous avons montré que la RhoGTPase Rac1 active le complexe Wave spécifiquement à l’extrémité du lamellipode. Dans une seconde étude, nous avons révélé que la localisation du complexe Wave est régulée par la dynamique des filaments des réseaux branchés d’actine. Ces données soulignent l’importance du complexe Wave dans la formation du lamellipode et révèlent l’existence d’une régulation mécanique de la localisation du complexe Wave.Cell motility is an integrated process involved in critical phenomena such as axonal pathfinding and synaptic plasticity. Dysregulation of cell motility can induce metastasis and abnormal spine shapes observed in neuropsychiatric disorders like autism and schizophrenia. Therefore it is essential to understand how cell motility is regulated. Cell motility requires the formation of branched actin networks propelled by actin polymerization that lead to the formation of membrane protrusions such as the lamellipodium. Several actin regulatory proteins are involved in this process, such as Rac1 and the WAVE and ARP2/3 complexes. Using single protein tracking, we revealed key phenomena concerning the spatio-temporal regulation of lamellipodium formation by actin regulatory proteins. We found that the localization and activation of the WAVE complex was enzymatically regulated, but also mechanically. First, we showed that the Rac1 RhoGTPase activates the WAVE complex specifically at the tip of the lamellipodium. We also showed that WAVE complex localization is regulated by the dynamics of branched-network actin filaments. This study confirms the crucial role of the WAVE complex in lamellipodium formation and reveals the existence of a mechanical regulation of the localization of this complex in the cell

Recruitment of Perisomatic Inhibition during Spontaneous Hippocampal Activity In Vitro.

It was recently shown that perisomatic GABAergic inhibitory postsynaptic potentials (IPSPs) originating from basket and chandelier cells can be recorded as population IPSPs from the hippocampal pyramidal layer using extracellular electrodes (eIPSPs). Taking advantage of this approach, we have investigated the recruitment of perisomatic inhibition during spontaneous hippocampal activity in vitro. Combining intracellular and extracellular recordings from pyramidal cells and interneurons, we confirm that inhibitory signals generated by basket cells can be recorded extracellularly, but our results suggest that, during spontaneous activity, eIPSPs are mostly confined to the CA3 rather than CA1 region. CA3 eIPSPs produced the powerful time-locked inhibition of multi-unit activity expected from perisomatic inhibition. Analysis of the temporal dynamics of spike discharges relative to eIPSPs suggests significant but moderate recruitment of excitatory and inhibitory neurons within the CA3 network on a 10 ms time scale, within which neurons recruit each other through recurrent collaterals and trigger powerful feedback inhibition. Such quantified parameters of neuronal interactions in the hippocampal network may serve as a basis for future characterisation of pathological conditions potentially affecting the interactions between excitation and inhibition in this circuit

Antioxidant effect of an aqueous extract of alga Cystoseira stricta during the frozen storage of Atlantic Chub mackerel (Scomber colias)

7 pages, 3 tablesAn aqueous extract of alga Cystoseira stricta was included in the glazing medium employed during the frozen storage of Atlantic Chub mackerel (Scomber colias). Rancidity stability of frozen fish muscle was determined throughout a 9-month storage at ‒18 ºC. An inhibitory effect on the development of lipid oxidation (assessment of peroxides, thiobarbituric acid and fluorescence indices) was observed as a result of the alga extract presence in the glazing system; thus, a marked retention of polyunsaturated fatty acids and alpha-tocopherol contents was achieved. Furthermore, an inhibitory effect on the lipid hydrolysis development and trimethylamine formation was implied as a result of the alga extract presence. Interestingly, enhancement of rancidity stability in frozen mackerel was found stronger by increasing the concentration of the alga extract in the glazing medium. A preservative effect of aqueous alga extract is established, this effect being attributed to the presence of potential active compounds able to stabilise radicals responsible for the lipid oxidation developmentThis work was supported by the Consejo Superior de Investigaciones Científicas (CSIC, Spain; project PIE 201370E001)Peer reviewe

Chemical composition and nutritional value of different seaweeds from the west Algerian coast

15 pages, 6 tables, 2 figuresAnalysis of proximate composition, lipid fraction (fatty acids and lipid classes), macroelements, and trace elements was carried out on brown (Cystoseira stricta; Cystoseira compressa), red (Corallina elongata), and green (Enteromorpha compressa; Ulva lactuca) seaweeds collected from the west Algerian coast to assess their nutritional value. Protein, lipid, carbohydrate, and ash content (g kg−1 dry alga) was in the ranges 58.5–141.4, 6.4–27.1, 134.0–461.1, and 246.1–764.2, respectively. The lowest caloric value was obtained for C. elongata (827.6 kcal kg−1 dry alga); the remaining values being in the range 2,106–2,479 kcal kg−1 dry alga. C. elongata and C. stricta provided the highest polyunsaturated fatty acid content, while a valuable n-6/n-3 ratio of between 0.95 and 4.20 was obtained for all species. α-Tocopherol was present in all seaweeds; the highest level was obtained in U. lactuca. Macroelements K and Na were predominant in C. compressa and C. stricta; while Mg and Ca were most abundant in E. compressa and C. elongata, respectively. In all cases, a healthy Na/K value < 0.7 was observed, and a profitable ion quotient ratio was observed in all cases, except for C. elongata. Estimated daily intake of most minerals from the algae studied is lower than the corresponding recommended daily intakeThanks to Department of Biology, Institute of Exact Sciences and Natural and Life Sciences, University Centre Ahmed Zabana of Relizane (Algeria) for the financial support of the internship of Mrs. Hanane Oucif. This work was supported by the Consejo Superior de Investigaciones Científicas (CSIC, Spain; project PIE 201370E001)Peer reviewe

Individual and pooled statistics for spike and eIPSP recruitment.

<p>Linear regression statistics parameters (<b>r²</b>, <b>F</b>, <b>p</b>; <b>Absolute</b> and <b>Relative</b> to shuffle: see methods) for the recruitment of action potentials (<b>p(AP triggering AP)</b>) and eIPSPs (<b>p(AP triggering eIPSP)</b>), for individual animals (<b>#1–3</b> in each species), and <b>pooled data</b>, as presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066509#pone-0066509-g004" target="_blank">Fig. 4C–F</a>.</p

eIPSPs induced by single interneurons and pyramidal cells in CA3.

<p>A–E. eIPSPs triggered by the discharge of single action potentials by a CA3 parvalbumin positive basket cell and by a pyramidal cell. Both neurons were recorded intracellularly in the CA3 pyramidal layer of rat slices and filled with biocytin. A. Camera lucida drawing of the axon (black) and dendrites (blue) of the interneuron and position of the extracellular electrodes (grey areas e1 and e2); scale bar 25 µm; dotted lines indicate the borders of the hippocampal strata: lacumosum-moleculare (slm), radiatum, lucidum, pyramidale and oriens. B. Immunohistochemical characterization of the same cell; scale bar 50 µm. Note perisomatic projection (A), parvalbumin positive (B, PV) and somatostatin negative (B, SOM) labelling. C. A single action potential from this cell (c bottom, averaged trace, scale bar 3 mV) was associated with an eIPSP in the CA3 pyramidal layer at the recording site corresponding to the interneuron projection area (e1, upper traces, 15 superimposed sweeps) but not at another recording site outside this area (e2, lower traces). D. photograph of the recorded and biocytin labeled pyramidal cell; scale bar 20 µm; <b>white spot</b>, extracellular recording site. Note the thorny excrescences on the proximal apical dendrites. E. eIPSPs (upper traces, 15 superimposed sweeps) triggered by the discharge of single action potentials (bottom, averaged trace, scale bar 10 mV) by the morphologically identified CA3 pyramidal cell shown in D. F–I. Amplitudes and latencies of eIPSPs evoked by the discharge of single spikes from individual interneurons (iNn) and pyramidal cells (pyr) recorded intracellularly. F. Average amplitude (one point per presynaptic neuron) of the evoked eIPSPs. G. Distribution of the amplitudes (mean±SEM) of the evoked eIPSPs. H. Average latencies (one point per presynaptic neuron) of the evoked eIPSPs. I. Distribution of the latencies (mean±SEM) of the evoked eIPSPs. Note that the distribution of interneuronal spikes to eIPSP latencies suggests monosynaptic transmission, while the longer latencies of eIPSPs evoked by pyramidal cells spikes suggest disynaptic transmission. Inset shows example histograms of eIPSP latencies for the interneuron shown in A (iNnd, blue bars) and for the pyramidal cell shown in D (pyr, black bars).</p

Recruitment of neuronal firing and inhibition in the CA3 circuit.

<p>A. The number of action potentials (AP, vertical bars and green arrow) within a 10 ms sliding window (time step 1 ms) was used to quantify the probability (see methods) for spike discharge to trigger action potentials (Pre-AP, light grey) or eIPSPs (Pre-eIPSP, light blue). Vertical blue line and arrow, eIPSP peak. B. Vertical bars show the probability (averaged from 9 animals) that an AP (left, grey) or eIPSP (right, blue) was preceded by a given number of spikes (within 10 ms). Note that only few (<10%) events (AP or eIPSPs) were preceded by more than 1 spike. C–F. Graphs showing the probability (absolute and relative to chance, see methods) that a given number of spikes (X axis) triggered a spike (<b>C, D</b>) or an eIPSP (<b>E, F</b>). Broken lines, individual animals (dotted lines, mice; dashed lines, guinea pigs rats; plain lines, rats); dots/squares, average values; thick lines, linear fit (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066509#pone-0066509-t001" target="_blank">Table 1</a> for corresponding R² and p values). Note the increasing probability of recruitment relative to chance (<b>D, F</b>), suggestive of neuronal cooperation in the circuit, and the modest absolute probabilities (<12% for eIPSP recruitment), suggestive of globally low levels of recruitment in the circuit.</p