Transcriptional Regulation of PEN-2, a Key Component of the γ-Secretase Complex, by CREB

Abstract

Gamma-secretase, which is responsible for the intramembranous cleavage of Alzheimer's β-amyloid precursor protein (APP), the signaling receptor Notch, and many other substrates, is a multiprotein complex consisting of at least four components: presenilin (PS), nicastrin, APH-1, and PEN-2. Despite the fact that PEN-2 is known to mediate endoproteolytic cleavage of full-length PS and APH-1 and nicastrin are required for maintaining the stability of the complex, the detailed physiological function of each component remain elusive. Unlike that of PS, the transcriptional regulation of PEN-2, APH-1, and nicastrin has not been investigated. Here, we characterized the upstream regions of the human PEN-2 gene and identified a 238-bp fragment located 353 bp upstream of the translational start codon as the key region necessary for the promoter activity. Further analysis revealed a CREB binding site located in the 238-bp region that is essential for the transcriptional activity of the PEN-2 promoter. Mutation of the CREB site abolished the transcriptional activity of the PEN-2 promoter. Electrophoretic mobility shift assays and chromatin immunoprecipitation analysis showed the binding of CREB to the PEN-2 promoter region both in vitro and in vivo. Activation of the CREB transcriptional factor by forskolin dramatically promoted the expression of PEN-2 mRNA and protein, whereas the other components of the γ-secretase complex remained unaffected. Forskolin treatment slightly increases the secretion of soluble APPα and Aβ without affecting Notch cleavage. These results demonstrate that expression of PEN-2 is regulated by CREB and suggest that the specific control of PEN-2 expression may imply additional physiological functions uniquely assigned to PEN-2.

This work was supported in part by National Institutes of Health grants (RO1 NS046673 to H.X., RO1 AG024895 to H.X., and RO1 DC006497 to Z.Z.); grants from the American Health Assistance Foundation (to H.X.) and the Alzheimer's Association (to H.X. and Z.Z.); and funds from the National Natural Science Foundation of China, no. 30370737, China's 863 project (2002BA711A07) and 973 project (2004CB518601, 2001CB510302). Y.-W.Z. is the recipient of National Institutes of Health training grant F32 AG024895.