[Frontiers in Bioscience E2, 22-35, January 1, 2010]

Transcriptional regulation of the presenilin-1 gene controls gamma-secretase activity

Sebum Lee1, Hriday K. Das1,2

1Department of Pharmacology and Neuroscience, University of North Texas Health Science Center at Fort Worth, 3500 Camp Bowie Boulevard, Fort Worth, Texas 76107, 2Department of Molecular Biology and Immunology, and Institute of Cancer Research, University of North Texas Health Science Center at Fort Worth, 3500 Camp Bowie Boulevard, Fort Worth, Texas 76107

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Materials and Methods
3.1. Cell culture
3.2. Western blot analysis
3.3. RT-PCR analysis
3.4. Transfection of APP, p53, ZNF237, CHD3, and Ets2 expression vectors
3.5. Abeta 1-40 Enzyme-Linked Immunosorbent Assay (ELISA)
3.6. Chromatin immunoprecipitation (ChIP) assay
3.7. Statistical Analysis
4. Results
4.1. JNK inhibitor SP600125 and JNK1 siRNA decrease the Abeta40 level in human neuroblastoma SK-N-SH cells
4.2. p53 inhibits PS1 transcription by deacetylation of histone at the PS1 promoter and, decreases PS1 protein and the Abeta40 levels in human neuroblastoma SK-N-SH cells
4.3. ZNF237 and CHD3 decrease PS1 protein and Abeta40 levels in human neuroblastoma SH-SY5Y cells by suppressing PS1 transcription via deacetylation of histone at the PS1 promoter
4.4. Ets2 transcription factor enhances PS1 protein and Abeta40 levels in human neuroblastoma SK-N-SH cells by activation of PS1 transcription via increased acetylation of histone at the PS1 promoter
4.5. JNK inhibitor SP600125 and Ets2 transcription factor do not alter the expression of another PS1/gamma-secretase component nicastrin (NCT)
4.6. HDAC inhibitor trichostatin-A (TSA) inceases histone acetylation and augments PS1 expression in SK-N-SH cells
5. Discussion
6. Acknowledgement
7. References

1. ABSTRACT

Inhibition of basal JNK activity by JNK inhibitor SP600125 or JNK1siRNA repressed presenilin-1 (PS1) expression in SK-N-SH cells by augmenting the level of p53, a repressor of the PS1 gene (1). We now showed that repression of PS1 transcription by JNK inhibitor SP600125 inhibited gamma-secretase mediated processing of amyloid precursor protein (APP) resulting in the accumulation of C99 fragment and the reduction of secreted Abeta40 level without altering the expression of nicastrin (NCT). Co-treatment of cells with SP600125 and p53 inhibitor, pifithrin-alpha, partially nullified the suppressive effects of SP610025 on PS1 expression and secreted Abeta40 level. Suppression of JNK1 by JNK1siRNA also decreased Abeta40 level. Furthermore, overexpression of the repressors p53, ZNF237 and CHD3 of the PS1 gene also suppressed the processing of APP through repression of PS1 transcription by deacetylation of histone at the PS1 promoter. Transcriptional activator Ets2 increased PS1 protein and secreted Abeta40 levels without affecting the expression of NCT by activating PS1 transcription via hyper-acetylation of histone at the PS1 promoter. Therefore, regulation of PS1 transcription modulates gamma-secretase activity.