Faculty Bibliography

The calcium-activated protease calpain cleaves a variety of biologically important proteins and serves, therefore, as a key regulator of many cellular functions. Activation of both main isoforms, calpain 1 and calpain 2, was demonstrated previously in Alzheimer's disease. In this report, antibodies specifically recognizing the active form of calpain 2 were used to investigate calpain 2 activation in a broad range of neurodegenerative diseases, utilizing multiple-label confocal immunofluorescence imaging. With rare exceptions, the active form of calpain 2 was found in colocalization with hyperphosphorylated tau protein. Aggregates of mutated huntingtin, alpha-synuclein, or unidentified protein in motor neuron disease type of frontotemporal dementia were always negative. These findings indicate that calpain 2 activation is not a general response to protein aggregation. In tauopathies, more pathological inclusions were labeled for hyperphosphorylated tau than for activated calpain 2. The extent of colocalization varied in both a disease-specific and cell-type specific manner. The active form of calpain 2 was detected in 50-75% of tau neurofibrillary pathology in Alzheimer's disease, Alzheimer neurofibrillary changes and Down's syndrome, as well as in the accompanying Alzheimer-type tau pathology in diffuse Lewy bodies disease, progressive supranuclear palsy, and corticobasal degeneration. For glial cells, only 10-25% of tuft-shaped astrocytes, glial plaques, or coiled bodies contained activated calpain 2. The majority of Pick bodies were negative. The association of calpain 2 activation with hyperphosphorylated tau might be the result of an attempt by the calpain proteolytic system to degrade the tau protein aggregates. Alternatively, calpain 2 could be directly involved in tau hyperphosphorylation by modulating protein kinase activities. Overall, these results provide evidence of the important role of the calpain proteolytic system in the pathogenesis of neurodegenerative diseases with tau neurofibrillary pathology

Activation of the calpain system might contribute to the impairment of synaptic transmission inAlzheimer's disease (AD) (Liu et al., 1999; Rapoport, 1999; Selkoe, 1994). Calpains regulate the function of many proteins by limited proteolysis and initiate the complete degradation of other proteins. In particular, they modulate processes that govern the function and metabolism of proteins key to the pathogenesis of AD, including tau and amyloid precursor protein (APP). (Xie and Johnson, 1998; Wang, 2000). We have found that overexpression of APP(K670M:N671L) and PS1(M146L) proteins in hippocampal cultures derived from transgenic mice causes an increase in the frequency of spontaneous release of neurotransmitter. We have also found that calpain immunoreactive clusters are co-localized with immunoreactivity for the vesicle-associated presynaptic marker, synaptophysin. Moreover, application of calpain inhibitor reduces the frequency of spontaneous release of neurotransmitter. Therefore, we have hypothesized that calpains might contribute to the increase in transmitter release. Based on this hypothesis, we propose to test whether it is possible to restore normal synaptic transmission between cells derived from the transgenic model of AD by using calpain inhibitors. The transgenic mouse model also shows spatial learning impairment, a phenomenon that is thought to be associated with plastic changes at synaptic level. Therefore, we will also test whether we can rescue the learning impairment through a treatment with calpain inhibitors

BACKGROUND: Several lines of evidence indicate the altered function of the temporal lobe, including the hippocampus and entorhinal cortex (EC), is associated with schizophrenia. We used single-cell gene expression technologies to assess coordinate changes in the expression of multiple genes, including neuronal signaling and synaptic-related markers in EC layer II stellate neurons. METHODS: We used a single-neuron microdissection technique coupled with linear antisense RNA amplification and high density/candidate gene arrays to assess coordinate changes in gene expression. The expression and relative abundance of more than 18,000 messenger RNAs were assessed from EC layer II stellate neurons from postmortem samples of schizophrenic and age-matched control brains. Results of this initial screen were used to perform a more specific secondary messenger RNA screen for each subject. RESULTS: Data disclosed marked differences in expression of various G-protein-coupled receptor-signaling transcripts, glutamate receptor subunits, synaptic proteins, and other transcripts. Results of secondary screening showed significant decreases in levels of G-protein subunit i(alpha)1, glutamate receptor 3, N-methyl-D-aspartate receptor 1, synaptophysin, and sensory nerve action potentials 23 and 25 in the stellate neurons of schizophrenic patients. We observed down-regulation of phospholemman (a phosphoprotein associated with anion channel formation) messenger RNA and protein levels in layer II/III stellate neurons in the population with schizophrenia. CONCLUSIONS: These results provide a preliminary expression profile of schizophrenia in defined neuronal populations. Understanding the coordinated involvement of multiple genes in human disease provides insight into the molecular basis of the disease and offers new targets for pharmacotherapeutic intervention.