anisomycin and lactacystin

For decades there has been a consensus that de novo protein synthesis is necessary for long-term memory. A second round of protein synthesis has been described for both extinction and reconsolidation following an unreinforced test session. Recently, it was shown that consolidation and reconsolidation depend not only on protein synthesis but also on protein degradation by the ubiquitin-proteasome system (UPS), a major mechanism responsible for protein turnover. However, the involvement of UPS on consolidation and reconsolidation of object recognition memory remains unknown. Here we investigate in the CA1 region of the dorsal hippocampus the involvement of UPS-mediated protein degradation in consolidation and reconsolidation of object recognition memory. Animals with infusion cannulae stereotaxically implanted in the CA1 region of the dorsal hippocampus, were exposed to an object recognition task. The UPS inhibitor β-Lactacystin did not affect the consolidation and the reconsolidation of object recognition memory at doses known to affect other forms of memory (inhibitory avoidance, spatial learning in a water maze) while the protein synthesis inhibitor anisomycin impaired the consolidation and the reconsolidation of the object recognition memory. However, β-Lactacystin was able to reverse the impairment caused by anisomycin on the reconsolidation process in the CA1 region of the hippocampus. Therefore, it is possible to postulate a direct link between protein degradation and protein synthesis during the reconsolidation of the object recognition memory.

Topics: Acetylcysteine; Animals; Anisomycin; CA1 Region, Hippocampal; Catheters, Indwelling; Cysteine Proteinase Inhibitors; Male; Neuropsychological Tests; Proteasome Endopeptidase Complex; Protein Synthesis Inhibitors; Proteolysis; Rats, Wistar; Recognition, Psychology; Ubiquitin

Exposure to a novel environment enhances the extinction of contextual fear. This has been explained by tagging of the hippocampal synapses used in extinction, followed by capture of proteins from the synapses that process novelty. The effect is blocked by the inhibition of hippocampal protein synthesis following the novelty or the extinction. Here, we show that it can also be blocked by the postextinction or postnovelty intrahippocampal infusion of the NMDA receptor antagonist 2-amino-5-phosphono pentanoic acid; the inhibitor of calcium/calmodulin-dependent protein kinase II (CaMKII), autocamtide-2-related inhibitory peptide; or the blocker of L-voltage-dependent calcium channels (L-VDCCs), nifedipine. Inhibition of proteasomal protein degradation by β-lactacystin has no effect of its own on extinction or on the influence of novelty thereon but blocks the inhibitory effects of all the other substances except that of rapamycin on extinction, suggesting that their action depends on concomitant synaptic protein turnover. Thus, the tagging-and-capture mechanism through which novelty enhances fear extinction involves more molecular processes than hitherto thought: NMDA receptors, L-VDCCs, CaMKII, and synaptic protein turnover.

Topics: Acetylcysteine; Animals; Anisomycin; Behavior, Animal; Calcium Channel Blockers; Conditioning, Classical; Excitatory Amino Acid Antagonists; Fear; Hippocampus; Proteasome Endopeptidase Complex; Protein Kinase Inhibitors; Rats; Sirolimus; Ubiquitin

The formation of long-term memory requires protein synthesis, particularly during initial memory consolidation. This process also seems to be dependant upon protein degradation, particularly degradation by the ubiquitin-proteasome system. The aim of this study was to investigate the temporal requirement of protein synthesis and degradation during the initial consolidation of allocentric spatial learning. As memory returns to a labile state during reactivation, we also focus on the role of protein synthesis and degradation during memory reconsolidation of this spatial learning. Male CD1 mice were submitted to massed training in the spatial version of the Morris water maze. At various time intervals after initial acquisition or after a reactivation trial taking place 24 h after acquisition, mice received an injection of either the protein synthesis inhibitor anisomycin or the protein degradation inhibitor lactacystin. This injection was performed into the hippocampal CA3 region, which is specifically implicated in the processing of spatial information. Results show that, in the CA3 hippocampal region, consolidation of an allocentric spatial learning task requires two waves of protein synthesis taking place immediately and 4 h after acquisition, whereas reconsolidation requires only the first wave. However, for protein degradation, both consolidation and reconsolidation require only one wave, taking place immediately after acquisition or reactivation, respectively. These findings suggest that protein degradation is a key step for memory reconsolidation, as for consolidation. Moreover, as protein synthesis-dependent reconsolidation occurred faster than consolidation, reconsolidation did not consist of a simple repetition of the initial consolidation.

Topics: Acetylcysteine; Animals; Anisomycin; Cysteine Proteinase Inhibitors; Hippocampus; Long-Term Potentiation; Male; Maze Learning; Memory; Mice; Nerve Tissue Proteins; Neurons; Protein Synthesis Inhibitors; Space Perception

Stress signals elicit a wide variety of cellular responses, many of which converge on the phosphorylation of JNK and p38 kinases, the activation of which has been well-characterized. How these kinases are switched off by dephosphorylation is not well understood. Here we describe how diverse cellular stresses affect differently the stability and activity of a JNK-inactivating dual-specificity threonine-tyrosine phosphatase M3/6. Both anisomycin and arsenite activate the JNK pathway and, in addition, inactivate the M3/6 phosphatase. However, while anisomycin treatment of cells leads to M3/6 protein degradation, arsenite appears to inactivate M3/6 directly. These results might have implications for the mechanism of tumour promotion by arsenic.

Topics: Acetylcysteine; Anisomycin; Arsenites; Cell Line, Transformed; Cysteine Proteinase Inhibitors; Dual-Specificity Phosphatases; Enzyme Stability; Humans; JNK Mitogen-Activated Protein Kinases; Kinetics; MAP Kinase Signaling System; Mitogen-Activated Protein Kinases; Models, Biological; Phosphoproteins; Protein Tyrosine Phosphatases; Transfection