The impact of amyloid precursor protein signalling and histone deacetylase inhibition on neprilysin expression in human prostate cells

Abstract

The zinc metallopeptidase, neprilysin (NEP), is an endothelin-1 degrading enzyme whose expression is extensively downregulated in prostate cancer. The expression of NEP in neuronal cells is regulated by intramembrane proteolysis of the amyloid precursor protein (APP) through its intracellular domain (AICD) facilitating histone acetylation of the NEP promoter and gene transcription. The present study has examined whether similar mechanisms operate in prostate cell lines. The expression of APP and its processing enzymes (b-and c-secretases) was examined in a number of prostate cell lines, and the effect of c-secretase inhibition was explored on NEP expression and activity. The potential interaction of AICD with the NEP promoter was examined by chromatin immunoprecipitation. Our results indicated that all key components involved in APP processing were expressed in prostate cancer cell lines but suppression of AICD production using a c-secretase inhibitor did not decrease NEP expression and activity, and no direct AICD-NEP promoter interaction could be detected. However, histone deacetylase inhibitors (valproate and trichostatin A) caused a 2-to 3-fold increase in NEP expression in PC-3 cells, and combinatorial treatment with the DNA demethylating agent, AzaC, further increased NEP expression levels. Although AICD is detectable in prostate cell lines, it does not appear to regulate NEP by AICD-mediated signalling. Apart from promoter demethylation, the data suggest that histone acetylation may facilitate partial re-activation of NEP expression in advanced prostate cancer cells. Upregulation of this tumour-suppressing protein may provide a novel therapeutic strategy in prostate cancer.Prostate cancer (PC) is the most frequently diagnosed cancer in western males. Advanced PC in the androgen-independent, chemo-refractory state is extremely life-threatening and currently incurable. In the progression of PC to the more malignant, androgen-independent phenotype, loss of a membrane-bound zinc metallopeptidase, neprilysin (NEP), is commonly found.1,2 NEP is an integral membrane glycoprotein and ectoenzyme which serves to inactivate circulating regulatory peptides.3 NEP has a wide tissue expression including intestinal and kidney epithelium, brain, skeletal muscle, lung and prostate. [4][5][6][7][8] NEP is able to inhibit cancer cell proliferation, migration and promote cell apoptosis during chemotherapy either via degradation of mitogenic neuropeptides such as endothelin-1 (ET-1), or by its direct protein-protein interactions with tumour suppressor PTEN, phosphatidylinositol 3-kinase (PI3K) and ezrin/radixin/moesin (ERM) proteins. 9 In prostate cancer cell lines, there is a reciprocal relation between expression levels of the ET-1 synthetic enzyme, endothelin-converting enzyme-1 (ECE-1) and the ET-1 degrading enzyme, NEP.2 Hence, downregulation of ECE-1 10 or upregulation of NEP 11 are proposed as viable therapeutic strategies in advanced prostate cancer.In the prostate, NEP expression is positively regulated by androgens, ...

Curcumin Inhibits the AKT/NF-κB Signaling via CpG Demethylation of the Promoter and Restoration of NEP in the N2a Cell Line

“…Further, we found treatment of 5-aza-CdR, the wellknown cytosine methylation inhibitor (29), resulted in remarkable increases of NEP expression in N2a/wt and N2a/ APPswe cells, which is consistent with the upregulation of NEP induced by 5-aza-CdR in other age-associated diseases such as prostate cancer (16,35). These data indicate that Fig.…”

Epigenetic Induction of EGR-1 Expression by the Amyloid Precursor Protein during Exposure to Novelty

“…It has been however established that nuclear location of AICD and consequent transcriptional regulation is dependent on APP processing through the amyloidogenic pathway [25,26,27]. Although regulation of gene transcription by AICD has been a matter of debate [28,29], probably reflecting the cell specificity of AICD regulation [30,31,32], it has been demonstrated by chromatin immunoprecipitation studies that AICD does interact with promoter regions of putatively regulated genes [24,25]. Here, we have demonstrated that the cleavage of APP by the γ-secretase activity to release AICD is not necessary for APP-mediated regulation of EGR-1 expression, and that AICD does not interact with the EGR-1 promoter in chromatin immunoprecipitation studies.…”

PS Dependent APP Cleavage Regulates Glucosylceramide Synthase and is Affected in Alzheimer's Disease

“…In line with these findings, it has been recently reported that differentiated PC12 cells, treated with the γ-secretase inhibitor DAPT, show an increase in ganglioside level in neuritic terminals [62], further strengthening that PS proteolytic activity alters ganglioside homeostasis. Additionally, we and others recently found that cleavage products of APP are involved in the regulation of several proteins and that this regulation is disturbed in absence of PS, in mutated PS or in AD [11,30,31,32,63,64,65]. Main focus was attended to the APP intracellular domain (AICD), which is released to the cytosol and discussed to be involved in gene transcription.…”