Cone Snail Glutaminyl Cyclase Sequences from Transcriptomic Analysis and Mass Spectrometric Characterization of Two Pyroglutamyl Conotoxins

Abstract

The post-translational modification of N-terminal glutamine (Q) to a pyroglutamyl (Z) residue is observed in the conotoxins produced by marine cone snails. This conversion requires the action of the enzyme glutaminyl cyclase (QC). Four complete QC sequences from the species C. araneosus, C. frigidus, C. litteratus, and C. monile and two partial sequences from C. amadis and C. miles have been obtained by analysis of transcriptomic data. Comparisons with mammalian enzyme sequences establish a high level of identity and complete conservation of functional active site residues, including a cluster of hydrogen-bonded acidic side chains. Mass spectrometric analysis of crude venom samples coupled to conotoxin precursor protein sequences obtained from transcriptomic data establishes the presence of pyroglutamyl conotoxins in the venom of C. frigidus and C. amadis. The C. frigidus peptide belongs to the M superfamily, with cysteine framework III, whereas the C. amadis peptide belongs to the divergent superfamily with cysteine framework VI/VII. Additionally, gamma carboxylation of glutamic acid and hydroxylation of proline are observed in the C. frigidus peptide. Mass spectral data are available via ProteomeXchange with identifier PXD009006.

A Combined Transcriptomics and Proteomics Approach Reveals the Differences in the Predatory and Defensive Venoms of the Molluscivorous Cone Snail Cylinder ammiralis (Caenogastropoda: Conidae)

“…The first peptide belonging to the U superfamily was reported in Cylinder textile, and its injection in mice triggered jumping and convulsion [ 48 ]. It was later found in C. victoriae [ 41 ], C. gloriamaris [ 26 ], and Leptoconus amadis [ 49 ]. Here, we detected this superfamily only in the defensive venom of C. ammiralis .…”

Size-Reduced Macrocyclic Analogues of [Pyr1]-apelin-13 Showing Negative Gα12 Bias Still Produce Prolonged Cardiac Effects

“…Apelin exists in several isoforms: apelin-36, apelin-17, apelin-13, [Pyr 1 ]-apelin-13, and [Pyr 1 ]-apelin-13 (1–12). Among them, [Pyr 1 ]-apelin-13 (Ape13) is the predominant isoform circulating in human plasma and heart tissues. ,− Apelin-13 can be generated from longer isoform such as preproapelin-55 or apelin-36 by the PCSK3 protease, , and the N-terminal glutamine can be cyclized to pyroglutamate to provide [Pyr 1 ]-apelin-13. , [Pyr 1 ]-apelin-13 (1–12) is generated from [Pyr 1 ]-apelin-13 upon angiotensin-converting enzyme 2 (ACE2) or prolylcarboxypeptidase (PRCP) cleavage. , In the cardiovascular system, apelin is a potent positive inotropic and vasodilator agent. , The therapeutic potential of the apelin/APJ system has been demonstrated both in animal models and in exploratory clinical trials. − Apelin improves animal survival in cardiovascular dysfunction induced by sepsis and restores cardiac parameters in the model of heart failure induced by transverse aortic constriction. , Early clinical trials in healthy subjects and patients with heart failure, , as well as patients suffering from pulmonary arterial hypertension (PAH), confirmed that treatment with apelin produced beneficial effects in humans and showed a real therapeutic perspective . In addition, the expression of apelin is increased under hypoxia , and stimulates the formation of new blood vessels, and many studies show its beneficial effect against the formation of skin ulcers, cardiac ischemia, or intracerebral hemorrhage in animal models. − All of the above suggests that the APJ receptor is a potential drug target, prompting both academics and industry to develop peptide analogues, small molecules, and functional antibodies targeting APJ. ,, …”

“…EC 50 3.7 nM) but a 10-fold lower potency and partial agonist profile on the Gα 12(27, EC 50 249 nM, E max 59% vs 1, EC 50 22 nM) and β-arrestin2 pathways (27, EC 50 β-arr2 743 nM, E max 69% vs 1, EC 50 126 nM). Interestingly, the modification of Nle11 on compound 27 with D-amino acids drastically changes the signaling profile of the resulting analogues 39−42.…”

Glutaminyl Cyclase, Diseases, and Development of Glutaminyl Cyclase Inhibitors

“…In 1963, the first glutaminyl cyclase (QC, also known as glutaminyl-peptide cyclotransferase, QPCT, EC 2.3.2.5) was isolated form the latex of a tropical plant ( Carica papaya ). , Since then, proteins catalyzing the same reaction have been identified and isolated from a wide range of pro- and eukaryotes. For example, these proteins, with molecular weights ranging between 33 and 40 kDa, have been identified in rat brain, porcine pituitary, bovine pituitary and spleen, human B lymphocytes, snake venom, bacterial pathogens, and even recently in cone snails. − QCs from different species exhibit overlapping but distinct homologies, structure, and characteristics. ,− The similarity in amino acid sequence, for instance, between the QC from the plant bacterial pathogen Xanthomonas campestris and the host plant is ∼20–30%, whereas the similarity in the amino acid sequence between QCs isolated from snake and human is ∼75% . The specificity constraints of QCs are dependent on the size and composition of the substrates.…”