|Presenilin-dependent gamma-secretase activity modulates neurite outgrowth. |
David J Figueroa, Jill A Morris, Lei Ma, Geeta Kandpal, Elizabeth Chen, Yue-Ming Li, Christopher P Austin
Neurobiology of disease
Demonstration that cleavage of both APP and Notch are dependent on the product of the early onset Alzheimer's disease gene, presenilin-1 (PS1), has raised the possibility that Notch function may be altered in AD. This finding also suggests that Notch may be affected by APPgamma-secretase inhibitors under development for the treatment of Alzheimer's disease, as these target PS1. Data that address these questions have been lacking, due to inability to specifically modulate PS1 activity in a system directly relevant to the adult human brain. Using novel highly specific inhibitors of PS1/gamma-secretase, we demonstrate that modulation of PS1 activity in human CNS neurons not only affects Abeta generation, but also has unanticipated effects on Notch and its activity. We demonstrate that intracellular trafficking of Notch in human CNS neurons is altered by inhibition of PS1 and is accompanied by dramatic changes in neurite morphology, consistent with inhibition of Notch activity. These data, together with immunohistochemical evidence of elevation of Notch pathway expression in AD brain, suggest that Notch dysregulation may contribute to the neuritic dystrophy characteristically seen in Alzheimer's disease brain. In addition, they raise the possibility that inhibition of gamma-secretase/PS1 may have clinically beneficial effects on the neuritic pathology of AD, in addition to its expected effect to reduce amyloid burden.
|Ultrastructural abnormality of sarcolemmal nuclei in Emery-Dreifuss muscular dystrophy (EDMD). |
Fidziańska, A, et al.
J. Neurol. Sci., 159: 88-93 (1998)
We performed ultrastructural studies on nuclear abnormalities in biopsied muscles from seven patients with EDMD, of three non-related families, and two sporadic cases. The diagnosis was based on clinical data and molecular findings. We detected different degrees of abnormalities in the sarcolemmal nuclei ranging from marked condensation of chromatin to complete damage of nuclear components. Other nuclei in the same muscle cell very often appeared normal. The extrusion of nuclear chromatin into sarcoplasm as a consequence of nuclear membrane disintegration was observed in numerous nuclei. All these nuclear changes are considered to be cytological indicators of nuclear dysfunction evoked by emerin deficiency.
|Characterization of HDJ-2, a human 40 kD heat shock protein. |
A R Davis, Y G Alevy, A Chellaiah, M T Quinn, T Mohanakumar, A R Davis, Y G Alevy, A Chellaiah, M T Quinn, T Mohanakumar
The international journal of biochemistry cell biology
Heat shock proteins (HSP) are a large and complex family of proteins that play important roles in cellular function and survival. In previous studies, cDNA for a 45 kD human HSP (HDJ-2) was cloned and shown to be homologous to DNA-J, a bacterial HSP [F.M. Ausubel, R. Brent, R. E. Kingston, D.D. Moore, J.G. Seidman, J.A. Smith, K. Struhl, Current Protocols in Molecular Biology, John Wiley and Sons, New York, 1997; A. Chellaiah, A. Davis, T. Mohanakumar, Cloning of a unique human homologue of the Escherichia coli DNAJ heat shock protein, Biochim. Biophys. Acta 1174 (1993) 111-113]. We have also shown that the expression of HDJ-2 is highly elevated in kidney allograft biopsies of kidneys undergoing rejection [Y.G. Alevy, D. Brennan, S. Durriya, T. Howard, T. Mohanakumar, Increased expression of the HDJ-2 heat shock protein in biopsies of human rejected kidneys, Transplantation 61 (1996) 963-967]. Because of the potential importance of HDJ-2 to disease pathogenesis, we carried out studies to characterize the structure and regulation of HDJ-2. Polyclonal and monoclonal antibodies that recognize recombinant HDJ-2 were prepared and used to localize its cellular expression. HDJ-2 was found to be farnesylated but not glycosylated. This HSP was ubiquitously expressed in all of the cell types we analyzed and was localized throughout the cytoplasm and around the nuclear membrane. However, upon heat shock it migrated to the Golgi, nucleolus, and the nuclear membrane. Northern blot analysis revealed two mRNA transcripts whose synthesis was not affected by heat shock. In addition, Western blot analysis showed that expression of HDJ-2 was also not affected by heat shock. Thus, our study shows the characterization of a HSP which, because of its migration pattern upon heat shock, is an excellent candidate for a protein chaperon.