Translational repression of the Disintegrin and Metalloprotease ADAM10 by a stable G-quadruplex secondary structure in its 5′-untranslated region

Model of the parallel ADAM10 5’UTR G-quadruplex secondary structure

Model of the parallel ADAM10 5’UTR G-quadruplex secondary structure. Guanines (red circles) of the canonical repeats of the G-rich stretches involved in G-quadruplex formation are located at the four edges of each plane marked in light red.

Background

Translation of the α-secretase ADAM10 is repressed by its 5′untranslated region (5′UTR).

Results

A G-rich region in the ADAM10 5′UTR forms a highly stable G-quadruplex secondary structure which inhibits translation of a luciferase reporter and ADAM10.

Conclusion

The G-quadruplex secondary structure is one inhibitory element for ADAM10 translation.

Significance

Our findings provide new insights in the translational regulation of ADAM10.

ABSTRACT

Anti-amyloidogenic processing of the amyloid precursor protein APP by α-secretase prevents formation of the amyloid-β-peptide which accumulates in senile plaques of Alzheimer disease patients. α-Secretase belongs to the family of a disintegrin and metalloproteases (ADAMs) and ADAM10 is the primary candidate for this anti-amyloidogenic activity. We recently demonstrated that ADAM10 translation is repressed by its 5′UTR and that in particular the first half of the ADAM10 5′UTR is responsible for translational repression. Here we asked if specific sequence motifs exist in the ADAM10 5′UTR that are able to form complex secondary structures and thus potentially inhibit ADAM10 translation. Using circular dichroism spectroscopy, we demonstrate that a G-rich region between nucleotides 66 and 94 of the ADAM10 5′UTR forms a highly stable, intramolecular, parallel G-quadruplex secondary structure under physiological conditions. Mutation of guanines in this sequence abrogates the formation of the G-quadruplex structure. While the G-quadruplex structure efficiently inhibits translation of a luciferase reporter in in vitro translation assays and in living cells, inhibition of G-quadruplex formation fails to do so. Moreover, expression of ADAM10 was similarly repressed by the G-quadruplex. Mutation of the G-quadruplex motif results in a significant increase of ADAM10 levels and consequently APPsα secretion. Thus we identified a critical RNA secondary structure within the 5′UTR which contributes to the translational repression of ADAM10.