Expression of the anti-amyloidogenic secretase ADAM10 is suppressed by its 5′-untranslated region

Proteolytic processing of the amyloid precursor protein by α-secretase prevents formation of the amyloid β-peptide (Aβ), which is the main constituent of amyloid plaques in brains of Alzheimer disease (AD) patients. α-Secretase activity is decreased in AD, and overexpression of the α-secretase ADAM10 (a disintegrin and metalloprotease 10) in an AD animal model prevents amyloid pathology. ADAM10 has a 444-nucleotide-long, very GC-rich 5′-untranslated region (5′-UTR) with two upstream open reading frames. Because similar properties of 5′-UTRs are found in transcripts of many genes, which are regulated by translational control mechanisms, we asked whether ADAM10 expression is translationally controlled by its 5′-UTR. We demonstrate that the 5′-UTR of ADAM10 represses the rate of ADAM10 translation. In the absence of the 5′-UTR, we observed a significant increase of ADAM10 protein levels in HEK293 cells, whereas mRNA levels were not changed. Moreover, the 5′-UTR of ADAM10 inhibits translation of a luciferase reporter in an in vitro transcription/translation assay. Successive deletion of the first half of the ADAM10 5′-UTR revealed a striking increase in ADAM10 protein expression in HEK293 cells, suggesting that this part of the 5′-UTR contains inhibitory elements for translation. Moreover, we detect an enhanced α-secretase activity and consequently reduced Aβ levels in the conditioned medium of HEK293 cells expressing both amyloid precursor protein and a 5′-UTR-ADAM10 deletion construct lacking the first half of the 5′-UTR. Thus, we provide evidence that the 5′-UTR of ADAM10 may have an important role for post-transcriptional regulation of ADAM10 expression and consequently Aβproduction.