Alzheimer Disease: Das HK

Das HK. · Department of Pharmacology and Neuroscience, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas 76107, USA. · Front Biosci. · Pubmed #17981591 No free full text.

Abstract: Two (amyloid and presenilin) hypotheses have been proposed to explain the pathogenesis of Alzheimer's disease (AD). According to amyloid hypothesis, the main amyloid plaques which are hallmark of AD are generated by beta- and gamma-secretase mediated proteolytic processing of amyloid precursor protein (APP). The amyloid hypothesis does not adequately address the pathogenesis of the disease, however, since transgenic mice that express the pathologic mutations of the APP and presenilin-1 (PS1) genes produce amyloid plaques but fail to exhibit neurodegeneration and memory loss observed in AD patients. According to presenilin hypothesis, loss of essential functions of PS due to decreased PS expression or mutations in the PS genes better explains the pathogenesis of AD. Recent studies have revealed that forebrain specific conditional knockouts of PS1 and PS2 genes (cPSKO) cause both neuronal degeneration and memory loss without evidence of formation of amyloid plaques. Another potential mechanism for the pathogenesis of AD may reside at the transcriptional regulation of the presenilin-1 gene. In this review, a detailed analysis of transcription factors that regulate PS1 transcription will be discussed. An in depth understanding of the regulatory mechanism of PS1 transcription can identify the targets that can potentially be used in therapeutic intervention of AD.

Das HK, Baez ML. · Department of Pharmacology and Neuroscience, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, USA. · Front Biosci. · Pubmed #18508445 No free full text.

Abstract: We have identified downstream promoter sequence of the PS1 gene that may be regulated by novel transcription factors. 3' deletion from +178 to +165 had no effect on PS1 transcription. 3' deletion from +178 to +140 decreased promoter activity by 50%. Further 3' deletion from +178 to +114 decreased promoter activity by 80%. Therefore, a crucial element controlling over 80% of the promoter activity in SK-N-SH cell line is located between +114 and +165. Electrophoretic mobility shift assays suggested that zinc finger proteins Sp1 and ADR1 interacted with the PS1 promoter sequence (+114 to +140) and promoter region (+140 to +165) respectively. A three base pair substitution within the core sequence (GGCGGGGA to GGCGactA) of the ADR1 consensus in the element (+140 to +165) that abolished ADR1-DNA interaction, reduced PS1 transcription by 50%. The substitution mutation in the sequence (+114 to +140) that abolished Sp1-DNA interaction had no effect on PS1 expression. These data suggest that a novel mammalian trans-activator protein ADR1 binds to the downstream element (+140 to +165) to activate PS1 transcription.

Pastorcic M, Das HK. · Department of Pharmacology and Neuroscience, University of North Texas Health Science Center at Fort Worth, 3500 Camp Bowie Boulevard, 76107, USA. · Brain Res Mol Brain Res. · Pubmed #12750007 No free full text.

Abstract: We have previously defined a crucial DNA element controlling 90% of the expression of the presenilin 1 gene at (-35 to +6). This region contains an Ets transcription factor binding motif, and a 2-base pair alteration within the core sequence (GGAA to TTAA) of the Ets consensus also reduced transcription by over 90%. We have shown that Ets1/2 transcription factors bind specifically to the -10 Ets element and activate PS1 transcription. The identification of other transcription factors recognizing specifically this promoter area should provide insights into the regulation of PS1. We have used the -10 Ets element as a bait in yeast one hybrid screening of a human brain cDNA library. This assay selected three factors from the Ets family: Ets2, ER81 and Elk1. We show that in vitro translated ER81 indeed binds specifically to the -10 region of the PS1 promoter and that ER81 activates by two- to threefold the basal transcription of a presenilin-1 promoter-chloramphenicol acetyltransferase reporter synthetic gene (-119, +178)PS1CAT in transient infection assays in neuroblastoma cells (SK-N-SH). GABPalpha, a member of the Ets family closely related to Ets2 and also containing a pointed domain, only increased PS1 transcription by about twofold. Cotransfection of GABPbeta together with GABPalpha did not increase PS1 transcription. However, GABPbeta alone activated PS1 transcription by two- to threefold. In contrast, the more distantly related Ets factor Elk1 repressed PS1 transcription very effectively.