calpain and Learning-Disabilities

Humanin and calmodulin-like skin protein (CLSP) inhibits Alzheimer disease (AD)-related neuronal cell death via the heterotrimeric humanin receptor in vitro. It has been suggested that CLSP is a central agonist of the heterotrimeric humanin receptor in vivo. To investigate the role of CLSP in the AD pathogenesis in vivo, we generated mouse CLSP-1 transgenic mice, crossed them with the APPswe/PSEN1dE9 mice, a model mouse of AD, and examined the effect of CLSP over-expression on the pathological phenotype of the AD mouse model. We found that over-expression of the mouse CLSP-1 gene attenuated spatial learning impairment, the loss of a presynaptic marker synaptophysin, and the inactivation of STAT3 in the APPswe/PSEN1dE9 mice. On the other hand, CLSP over-expression did not affect levels of Aβ, soluble Aβ oligomers, or gliosis. These results suggest that the CLSP-mediated attenuation of memory impairment and synaptic loss occurs in an Aβ-independent manner. The results of this study may serve as a hint to the better understanding of the AD pathogenesis and the development of AD therapy.

Topics: Alzheimer Disease; Animals; Brain; Calpain; Cytoskeletal Proteins; Intracellular Signaling Peptides and Proteins; Learning Disabilities; Maze Learning; Mice; Mice, Transgenic; Nerve Tissue Proteins; Neuroprotection; Presenilin-1; STAT3 Transcription Factor; Synaptophysin

In the central nervous system, two calpain isoforms are highly expressed: calpain1 and calpain2. Here, we show for the first time that activation of the calpain isoform, calpain2, is a necessary event in hippocampal synaptic plasticity and in learning and memory. We developed a fluorescence resonance energy transfer-based animal model to monitor in vivo calpain activation in single cells and in real time. Additionally, utilizing a novel rabies virus glycoprotein-chimeric peptide, which enabled the transvascular delivery of small interfering RNA to the brain against calpain2, we down-regulated the calpain2 isoform in vivo. Calpain2 gene silencing eliminated long-term potentiation and impaired learning and memory. Our results not only identify the calpain2 isoform as a critical mediator in learning and memory but also highlight an innovative, highly efficient calpain2-targeting peptide capable of isoform-specific gene silencing in the brain. We anticipate these innovative technologies and our better understanding of the calpain machinery, particularly of the calpain2 isoform, will have substantial influence on future translational studies, attracting considerable interest in the use of calpain models and calpain-specific inhibitors in the development of therapeutics.

Topics: Amino Acid Sequence; Animals; Brain-Derived Neurotrophic Factor; Calpain; Conditioning, Operant; Dipeptides; Drug Delivery Systems; Electroshock; Exploratory Behavior; Fear; Female; Fluorescence Resonance Energy Transfer; Freezing Reaction, Cataleptic; Glycoproteins; Learning Disabilities; Male; Memory Disorders; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microscopy, Confocal; Molecular Sequence Data; Nerve Tissue Proteins; Neuronal Plasticity; Peptide Fragments; Peptides; Receptors, Cholinergic; RNA Interference; RNA, Small Interfering; Single-Blind Method; Tetraethylammonium; Viral Proteins

The entorhinal cortex (EC) is one of the most vulnerable brain regions that is affected by beta amyloid (Aβ) in the early phases of Alzheimer's disease (AD). Calcium dyshomeostasis is one reason of Aβ pathology and the role of calcium channel blockers (CCBs) in this phenomenon has not fully understood. In this study, we investigated the possible neuroprotective effect of CCBs, nimodipine and isradipine against amyloid pathogenesis in EC. The Aβ 1-42 was injected bilaterally into the EC of male rats and spatial performance was assessed between 7 and 12 days after Aβ injection by Morris water maze test. Animals were daily treated by injection of various doses of nimodipine or isradipine (both at 3, 10, or 30 μg/2 μl) or their vehicles into the lateral ventricle until the start of behavioral test. Lesion in EC was assessed by measuring some proteinases involved in calcium dependent apoptotic pathway (calpain 2, caspase 12 and 3). Despite normal performance in probe test, Aβ treated rats showed delayed acquisition in a spatial reference memory task. Aβ treated rats revealed delayed acquisition in reversal memory and had deficit in probe test. The observed impairments were attenuated by isradipine (10 and 30 μg but not 3 μg) and nimodipine (30 μg). Calpain 2, caspase 12 and 3 were increased in the Aβ treated animals which was partially antagonized by isradipine and nimodipine. It is concluded that CCBs might have beneficial therapeutic effects in AD especially in the early phases of this disease.

Topics: Amyloid beta-Peptides; Analysis of Variance; Animals; Area Under Curve; Calcium Channel Blockers; Calpain; Caspases; Cell Death; Dose-Response Relationship, Drug; Humans; In Situ Nick-End Labeling; Isradipine; Learning Disabilities; Male; Maze Learning; Memory Disorders; Nimodipine; Peptide Fragments; Rats; Rats, Wistar; Reversal Learning; Time Factors

Tau-tubulin kinase-1 (TTBK1) is involved in phosphorylation of tau protein at specific Serine/Threonine residues found in paired helical filaments, suggesting its role in tauopathy pathogenesis. We found that TTBK1 levels were upregulated in brains of human Alzheimer' disease (AD) patients compared with age-matched non-AD controls. To understand the effects of TTBK1 activation in vivo, we developed transgenic mice harboring human full-length TTBK1 genomic DNA (TTBK1-Tg). Transgenic TTBK1 is highly expressed in subiculum and cortical pyramidal layers, and induces phosphorylated neurofilament aggregation. TTBK1-Tg mice show significant age-dependent memory impairment as determined by radial arm water maze test, which is associated with enhancement of tau and neurofilament phosphorylation, increased levels of p25 and p35, both activators of cyclin-dependent protein kinase 5 (CDK5), enhanced calpain I activity, and reduced levels of hippocampal NMDA receptor types 2B (NR2B) and D. Enhanced CDK5/p35 complex formation is strongly correlated with dissociation of F-actin from p35, suggesting the inhibitory mechanism of CDK5/p35 complex formation by F-actin. Expression of recombinant TTBK1 in primary mouse cortical neurons significantly downregulated NR2B in a CDK5- and calpain-dependent manner. These data suggest that TTBK1 in AD brain may be one of the underlying mechanisms inducing CDK5 and calpain activation, NR2B downregulation, and subsequent memory dysfunction.

Topics: Actins; Age Factors; Alzheimer Disease; Animals; Calpain; Cells, Cultured; Cerebral Cortex; Down-Regulation; Hippocampus; Humans; Learning Disabilities; Mass Spectrometry; Maze Learning; Mice; Mice, Transgenic; Microtubule-Associated Proteins; Molecular Weight; Nerve Tissue Proteins; Neurons; Nuclear Proteins; Protein Serine-Threonine Kinases; Receptors, N-Methyl-D-Aspartate; RNA, Small Interfering; Spatial Behavior; t-Complex Genome Region; Transfection; Up-Regulation