Effects of a Sensory Block on Calexcitin Levels in the Photoreceptors of <i>Hermissenda crassicornis</i>

Borley, Kimberly A.; Epstein, Herman T.; Kuzirian, Alan M.

doi:10.2307/1543394

Cited by 5 publications

(3 citation statements)

References 4 publications

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“…The increased levels of bryostatin-induced calexcitin were consistent with those of initial bryostatin studies (Scioletti et al, 2004) and with levels induced solely by associative conditioning (Kuzirian et al, 2001Borley et al, 2002). This study's data, however, indicated that bryostatin acting through PKC activation could induce calexcitin levels to rise irrespective of the training paradigm (Figs.…”

Section: Discussionsupporting

confidence: 87%

Bryostatin Enhancement of Memory inHermissenda

Kuzirian

Epstein

Gagliardi

et al. 2006

The Biological Bulletin

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Abstract. Bryostatin, a potent agonist of protein kinase C (PKC), when administered to Hermissenda was found to affect acquisition of an associative learning paradigm. Low bryostatin concentrations (0.1 to 0.5 ng/ml) enhanced memory acquisition, while concentrations higher than 1.0 ng/ml down-regulated the pathway and no recall of the associative training was exhibited. The extent of enhancement depended upon the conditioning regime used and the memory stage normally fostered by that regime. The effects of two training events (TEs) with paired conditioned and unconditioned stimuli, which standardly evoked only short-term memory (STM) lasting 7 min, were-when bryostatin was added concurrently-enhanced to a long-term memory (LTM) that lasted about 20 h. The effects of both 4-and 6-paired TEs (which by themselves did not generate LTM), were also enhanced by bryostatin to induce a consolidated memory (CM) that lasted at least 5 days. The standard positive 9-TE regime typically produced a CM lasting at least 6 days. Low concentrations of bryostatin (Ͻ0.5 ng/ml) elicited no demonstrable enhancement of CM from 9-TEs. However, animals exposed to bryostatin concentrations higher than 1.0 ng/ml exhibited no behavioral learning.Sharp-electrode intracellular recordings of type-B photoreceptors in the eyes from animals conditioned in vivo with bryostatin revealed changes in input resistance and an enhanced long-lasting depolarization (LLD) in response to light. Likewise, quantitative immunocytochemical measurements using an antibody specific for the PKC-activated Ca 2ϩ /GTP-binding protein calexcitin showed enhanced antibody labeling with bryostatin.Animals exposed to the PKC inhibitor bisindolylmaleimide-XI (Ro-32-0432) administered by immersion prior to 9-TE conditioning showed no training-induced changes with or without bryostatin exposure. However, if animals received bryostatin before Ro-32, the enhanced acquisition and demonstrated recall still occurred. Therefore, pathways responsible for the enhancement effects induced by bryostatin were putatively mediated by PKC.Overall, the data indicated that PKC activation occurred and calexcitin levels were raised during the acquisition phases of associative conditioning and memory initiation, and subsequently returned to baseline levels within 24 and 48 h, respectively. Therefore, the protracted recall measured by the testing regime used was probably due to bryostatininduced changes during the acquisition and facilitated storage of memory, and not necessarily to enhanced recall of the stored memory when tested many days after training.

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Section: Discussionsupporting

confidence: 87%

Bryostatin Enhancement of Memory inHermissenda

Kuzirian

Epstein

Gagliardi

et al. 2006

The Biological Bulletin

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“…Electrophysiological studies using recombinant squid calexcitin and human fibroblast inside-out patches also showed that the protein is capable of directly regulating K + -channel mean open time and probability in the presence of Ca 2+ (Nelson et al, 1996). Furthermore, investigation using sensory and chemical blocks during learning in Hermissenda established calexcitin as being necessary to establish and consolidate longterm memory (Kuzirian et al, 2001(Kuzirian et al, , 2003Borley et al, 2002;Child et al, 2003;Epstein et al, 2003). Additional experimental evidence has also implicated calexcitin in several mechanisms that could enable it to functionally alter neuronal physiology.…”

Section: Introductionmentioning

confidence: 99%

Binding of Gd³⁺to the neuronal signalling protein calexcitin identifies an exchangeable Ca²⁺-binding site

et al. 2016

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Calexcitin was first identified in the marine snail Hermissenda crassicornis as a neuronal-specific protein that becomes upregulated and phosphorylated in associative learning. Calexcitin possesses four EF-hand motifs, but only the first three (EF-1 to EF-3) are involved in binding metal ions. Past work has indicated that under physiological conditions EF-1 and EF-2 bind Mg 2+ and Ca 2+ , while EF-3 is likely to bind only Ca 2+ . The fourth EF-hand is nonfunctional owing to a lack of key metal-binding residues. The aim of this study was to use a crystallographic approach to determine which of the three metal-binding sites of calexcitin is most readily replaced by exogenous metal ions, potentially shedding light on which of the EF-hands play a 'sensory' role in neuronal calcium signalling. By co-crystallizing recombinant calexcitin with equimolar Gd 3+ in the presence of trace Ca 2+ , EF-1 was shown to become fully occupied by Gd 3+ ions, while the other two sites remain fully occupied by Ca 2+ . The structure of the Gd 3+ -calexcitin complex has been refined to an R factor of 21.5% and an R free of 30.4% at 2.2 Å resolution. These findings suggest that EF-1 of calexcitin is the Ca 2+ -binding site with the lowest selectivity for Ca 2+ , and the implications of this finding for calcium sensing in neuronal signalling pathways are discussed.

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“…Among these was the kenspeckle figure of James Stevens Curl, now regarded as one of Britain's most astute and prolific architectural historians, who was engaged to enable the Trust to coordinate Scotland's contribution to the celebration of European Architectural Heritage Year in 1975. 20 Another was Sadie Douglas, who later stayed on as office manager but who joined the Trust in 1974 to run a city-wide campaign, Facelift Glasgow, under contract from Glasgow Corporation. 21 The project began with the stone cleaning of the monumental column at the centre of George Square, erected to the memory of Sir Walter Scott and reputed to be the largest memorial in the world to commemorate an artistic figure. This exercise, sponsored by a firm of builders, marked the start of many years of endeavour to remove a century and more of grime from the stonework of Glasgow.…”

mentioning

confidence: 99%

The Early Years of the Scottish Civic Trust

Gerrard¹

2010

Architectural Heritage

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Effects of a Sensory Block on Calexcitin Levels in the Photoreceptors of Hermissenda crassicornis

Cited by 5 publications

References 4 publications

Bryostatin Enhancement of Memory inHermissenda

Bryostatin Enhancement of Memory inHermissenda

Binding of Gd³⁺to the neuronal signalling protein calexcitin identifies an exchangeable Ca²⁺-binding site

The Early Years of the Scottish Civic Trust

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Effects of a Sensory Block on Calexcitin Levels in the Photoreceptors of Hermissenda crassicornis

Cited by 5 publications

References 4 publications

Bryostatin Enhancement of Memory inHermissenda

Bryostatin Enhancement of Memory inHermissenda

Binding of Gd3+to the neuronal signalling protein calexcitin identifies an exchangeable Ca2+-binding site

The Early Years of the Scottish Civic Trust

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Binding of Gd³⁺to the neuronal signalling protein calexcitin identifies an exchangeable Ca²⁺-binding site