Synthesis, structure elucidation, in vitro biological activity, toxicity, and Caco-2 cell permeability of lipophilic analogues of alpha-conotoxin MII.
The alpha-conotoxin MII is a two disulfide bridge containing, 16 amino acid long peptide toxin isolated from the marine snail Conus magus. This toxin has been found to be a highly selective and potent inhibitor of neuronal nicotinic acetylcholine receptors (nAChRs) of the subtype alpha3beta2. To improve the bioavailability of this peptide, two lipidic analogues of MII have been synthesized, the first by coupling 2-amino-d,l-dodecanoic acid (Laa) to the N terminus (LaaMII) and the second by replacing Asn5 in the MII sequence with this lipoamino acid (5LaaMII). Both lipidic linear peptides were then oxidized under standard conditions. (1)H NMR shift analysis of these peptides and comparison with the native MII peptide showed that the tertiary structure of the N-conjugated analogue, LaaMII, was consistent with that of the native conotoxin, whereas the 5LaaMII analogue formed the correct disulfide bridges but failed to adopt the native helical tertiary structure. The N terminus conjugate was also found to inhibit nAChRs of the subtype alpha3beta2 with equal potency to the parent peptide, whereas the 5LaaMII analogue showed no inhibitory activity. The active LaaMII analogue was found to exhibit significantly improved permeability across Caco-2 cell monolayers compared to the native MII, and both peptides showed negligible toxicity.
Blanchfield
Joanne T
JT
School of Pharmacy, Institute for Molecular Bioscience, and School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia.
Dutton
Julie L
JL
Hogg
Ronald C
RC
Gallagher
Oliver P
OP
Craik
David J
DJ
Jones
Alun
A
Adams
David J
DJ
Lewis
Richard J
RJ
Alewood
Paul F
PF
Toth
Istvan
I
D000595:Amino Acid Sequence; D000818:Animals; D018938:Caco-2 Cells; D020916:Conotoxins / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics / Q000633:toxicity; D005726:Ganglia, Parasympathetic / Q000166:cytology; D006461:Hemolysis; D006801:Humans; D066298:In Vitro Techniques; D007850:Lauric Acids / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D018733:Nicotinic Antagonists / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics / Q000633:toxicity; D018408:Patch-Clamp Techniques; D010456:Peptides, Cyclic / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics / Q000633:toxicity; D010539:Permeability; D017434:Protein Structure, Tertiary; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000502:physiology; D012995:Solubility; D013329:Structure-Activity Relationship
D020916:Conotoxins; D007850:Lauric Acids; D018733:Nicotinic Antagonists; D010456:Peptides, Cyclic; D011978:Receptors, Nicotinic; C098872:alpha-conotoxin MII