A short framework-III (mini-M-2) conotoxin from the venom of a vermivorous species, Conus archon, inhibits human neuronal nicotinic acetylcholine receptors.

The venoms of Conus snails contain neuroactive peptides named conotoxins (CTXs). Some CTXs are nicotinic acetylcholine receptor (nAChRs) antagonists. nAChRs modulate the release of neurotransmitters and are implicated in several pathophysiologies. One venom peptide from Conus archon, a vermivorous species from the Mexican Pacific, was purified by RP-HPLC and its activity on human α7, α3ß2, and α7ß2 nAChRs was assessed by the two-electrode voltage clamp technique. At 36.3 µM the purified peptide (F27-1, renamed tentatively ArchIIIA) slowly reversibly inhibited the ACh-induced response of the hα7 subtype by 44.52 ± 5.83%, while it had low or no significant effect on the response of the hα3ß2 and hα7ß2 subtypes; the EC50 of the inhibiting effect was 45.7 µM on the hα7 subtype. This peptide has 15 amino acid residues and a monoisotopic mass of 1654.6 Da (CCSALCSRYHCLPCC), with three disulfide bridges and a free C-terminus. This sequence with a CC-C-C-CC arrangement (framework III) belongs to the M superfamily of conotoxins, corresponding to the mini-M´s (M-1-M-3) conotoxins; due to its size and inter-Cys spacings it is an M-2 conotoxin. This toxin is a novel mini-M conotoxin affecting ligand-gated ion channels, like the maxi-M CTX ψ-conotoxins and α-MIIIJ conotoxin (nAChRs blockers). This peptide seems to be homologous to the reg3b conotoxin (from Conus regius) with an identity of 93.3%, differing only in the third residue in the sequence, serine for threonine, both uncharged polar residues. We obtained, in silico, a probable 3D structure, which is consistent with its effect on neuronal subtypes.

First detection of an ocellate octopus in the Revillagigedos ecoregion, a biodiversity hotspot located in the Tropical East Pacific Province.

The biodiversity of mollusks, particularly cephalopods, has not been exhaustively determined in the Revillagigedos ecoregion, which is a biodiversity hotspot for several marine groups located in the Tropical East Pacific Province. In our study, we detected and examined ocellate octopuses from Socorro and Clarion Islands, and determined their identity using morphological criteria and molecular data from two mitochondrial genes (COIII and COI). The taxon identified was Octopus oculifer, a species considered endemic to the Galapagos Archipelago. In addition, according to our analyses, O. mimus, O. hubbsorum and O. oculifer are very closely related and may represent a species complex comprised of three morphotypes. We found that the evolutionary relationships among octopuses are not determined by the presence of ocelli. This study is the first to report a clade represented by ocellate and non-ocellate species, in addition, the identity of cephalopods in the Revillagigedos was determined with analytical support.

αD-Conotoxins in Species of the Eastern Pacific: The Case of Conus princeps from Mexico.

Conus snails produce venoms containing numerous peptides such as the α-conotoxins (α-CTXs), which are well-known nicotinic acetylcholine receptor (nAChR) antagonists. Thirty-eight chromatographic fractions from Conus princeps venom extract were isolated by RP-HPLC. The biological activities of 37 fractions (0.07 µg/µL) were assayed by two-electrode voltage clamp on human α7 nAChRs expressed in Xenopus laevis oocytes. Fractions F7 and F16 notably inhibited the response elicited by acetylcholine by 52.7 ± 15.2% and 59.6 ± 2.5%, respectively. Fraction F7 was purified, and an active peptide (F7-3) was isolated. Using a combination of Edman degradation, mass spectrometry, and RNASeq, we determined the sequence of peptide F7-3: AVKKTCIRSTOGSNWGRCCLTKMCHTLCCARSDCTCVYRSGKGHGCSCTS, with one hydroxyproline (O) and a free C-terminus. The average mass of this peptide, 10,735.54 Da, indicates that it is a homodimer of identical subunits, with 10 disulfide bonds in total. This peptide is clearly similar to αD-CTXs from species of the Indo-Pacific. Therefore, we called it αD-PiXXA. This toxin slowly and reversibly inhibited the ACh-induced response of the hα7 nAChR subtype, with an IC50 of 6.2 µM, and it does not affect the hα3ß2 subtype at 6.5 µM.

First report of partial albinism in the blue lobster Panulirusinflatus (Bouvier, 1895) from the Mexican Pacific (Crustacea, Decapoda, Palinuridae).

The first case of partial albinism registered in the Mexican Pacific by the blue lobster Panulirusinflatus is presented. The specimen was collected on the southern coast of Jalisco know as Punta "El Estrecho". It constitutes one of the few registered cases of albinism in invertebrates from the Eastern Tropical Pacific.

Diversity of A-conotoxins of three worm-hunting cone snails (Conus brunneus, Conus nux, and Conus princeps) from the Mexican Pacific coast.

Conus marine snails (∼500 species) are tropical predators that use venoms mainly to capture prey and defend themselves from predators. The principal components of these venoms are peptides that are known as "conotoxins" and generally comprise 7-40 amino acid residues, including 0-5 disulfide bridges and distinct posttranslational modifications. The most common molecular targets of conotoxins are voltage- and ligand-gated ion channels, G protein-coupled receptors, and neurotransmitter transporters, to which they bind, typically, with high affinity and specificity. Due to these properties, several conotoxins have become molecular probes, medicines, and leads for drug design. Conotoxins have been classified into genetic superfamilies based on the signal sequence of their precursors, and into pharmacological families according to their molecular targets. The objective of this work was to identify and analyze partial cDNAs encoding conotoxin precursors belonging to the A superfamily from Conus brunneus, Conus nux, and Conus princeps. These are vermivorous species of the Mexican Pacific coast from which only one A-conotoxin, and few O- and I2-conotoxins have been reported. Employing RT-PCR, we identified 30 distinct precursors that contain 13 different predicted mature toxins. With the exception of two groups of four highly similar peptides, these toxins are diverse at both the sequence and the physicochemical levels, and they belong to the 4/3, 4/4, 4/5, 4/6, and 4/7 structural subfamilies. These toxins are predicted to target diverse nicotinic acetylcholine receptor (nAChR) subtypes: nx1d, muscle; pi1a-pi1d, α3ß2, α7, and/or α9α10; br1a, muscle, α3ß4, and/or α4ß2; and nx1a-nx1c/pi1g and pi1h, α3ß2, α3ß4, α9ß10, and/or α7.