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Mar. Drugs 2012, 10(7), 1511-1527; doi:10.3390/md10071511
Article

Cyclisation Increases the Stability of the Sea Anemone Peptide APETx2 but Decreases Its Activity at Acid-Sensing Ion Channel 3

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*  and *
The University of Queensland, Institute for Molecular Bioscience, Brisbane, QLD 4072, Australia
* Authors to whom correspondence should be addressed.
Received: 30 May 2012 / Revised: 14 June 2012 / Accepted: 6 July 2012 / Published: 16 July 2012
(This article belongs to the Special Issue Sea Anemone Toxins)
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Abstract

APETx2 is a peptide isolated from the sea anemone Anthopleura elegantissima. It is the most potent and selective inhibitor of acid-sensing ion channel 3 (ASIC3) and it is currently in preclinical studies as a novel analgesic for the treatment of chronic inflammatory pain. As a peptide it faces many challenges in the drug development process, including the potential lack of stability often associated with therapeutic peptides. In this study we determined the susceptibility of wild-type APETx2 to trypsin and pepsin and tested the applicability of backbone cyclisation as a strategy to improve its resistance to enzymatic degradation. Cyclisation with either a six-, seven- or eight-residue linker vastly improved the protease resistance of APETx2 but substantially decreased its potency against ASIC3. This suggests that either the N- or C-terminus of APETx2 is involved in its interaction with the channel, which we confirmed by making N- and C-terminal truncations. Truncation of either terminus, but especially the N-terminus, has detrimental effects on the ability of APETx2 to inhibit ASIC3. The current work indicates that cyclisation is unlikely to be a suitable strategy for stabilising APETx2, unless linkers can be engineered that do not interfere with binding to ASIC3.
Keywords: sea anemone; peptide; APETx2; ASIC3; cyclisation; truncation; stability sea anemone; peptide; APETx2; ASIC3; cyclisation; truncation; stability
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Jensen, J.E.; Mobli, M.; Brust, A.; Alewood, P.F.; King, G.F.; Rash, L.D. Cyclisation Increases the Stability of the Sea Anemone Peptide APETx2 but Decreases Its Activity at Acid-Sensing Ion Channel 3. Mar. Drugs 2012, 10, 1511-1527.

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