Abstract
PcActx peptide, identified from the transcriptome of zoantharian Palythoa caribaeorum, was clustered into the phylogeny of analgesic polypeptides from sea anemone Heteractis crispa (known as APHC peptides). APHC peptides were considered as inhibitors of transient receptor potential cation channel subfamily V member 1 (TRPV1). TRPV1 is a calcium-permeable channel expressed in epileptic brain areas, serving as a potential target for preventing epileptic seizures. Through in silico and in vitro analysis, PcActx peptide was shown to be a potential TRPV1 channel blocker. In vivo studies showed that the linear and oxidized PcActx peptides caused concentration-dependent increases in mortality of zebrafish larvae. However, monotreatment with PcActx peptides below the maximum tolerated doses (MTD) did not affect locomotor behavior. Moreover, PcActx peptides (both linear and oxidized forms) could effectively reverse pentylenetetrazol (PTZ)-induced seizure-related behavior in zebrafish larvae and prevent overexpression of c-fos and npas4a at the mRNA level. The excessive production of ROS induced by PTZ was markedly attenuated by both linear and oxidized PcActx peptides. It was also verified that the oxidized PcActx peptide was more effective than the linear one. In particular, oxidized PcActx peptide notably modulated the mRNA expression of genes involved in calcium signaling and γ-aminobutyric acid (GABA)ergic-glutamatergic signaling, including calb1, calb2, gabra1, grm1, gria1b, grin2b, gat1, slc1a2b, gad1b, and glsa. Taken together, PcActx peptide, as a novel neuroactive peptide, exhibits prominent anti-epileptic activity, probably through modulating calcium signaling and GABAergic-glutamatergic signaling, and is a promising candidate for epilepsy management.
Highlights
The Phylum Cnidaria, containing almost 13,000 species, is classified into five main classes: Anthozoa, Cubozoa, Hydrozoa, Scyphozoa, and Staurozoa (Kayal et al, 2013)
Phylum Cnidaria represents a large number of bioactive peptide toxins that could contribute to the development of drug therapies, owing to their selective and specific interaction with diverse kinds of ion channels, including voltage-gated potassium (KV), calcium (CaV) and sodium (NaV) channels, the acid-sensing ion (ASIC) channel, and the TRPV1 channel (Mouhat et al, 2004)
Since analgesic polypeptides from sea anemone Heteractis crispa (APHC) peptides have been reported and confirmed as TRPV1 inhibitors, here we aimed to investigate the structure, bioactivity and mechanism of action of PcActx peptide identified from transcriptomics analysis of P. caribaeorum
Summary
The Phylum Cnidaria, containing almost 13,000 species, is classified into five main classes: Anthozoa, Cubozoa, Hydrozoa, Scyphozoa, and Staurozoa (Kayal et al, 2013). Stichodactyla toxin (ShK) and its analogs, which were found in the sea anemone Stichodactyla helianthus, could bind to the KV1.3 ion channel, potentially serving as effective therapies for autoimmune diseases (Castaneda et al, 1995; Norton et al, 2015). An analog of ShK, named ShK-186 or dalazatide, is currently in human clinical trials (Tarcha et al, 2017). Another example is the peptide APETx2, derived from sea anemone Anthopleura elegantissima (Diochot et al, 2004). A previous report showed that it exerted analgesic effects in an inflammatory pain model through inhibition of the ASIC3 channel (Karczewski et al, 2010). Two peptides from P. caribaeorum, namely PcShK and PcKuz, were shown to act on the KV ion channel and displayed neuroprotective and cardioprotective effects in vitro and in vivo (Liao et al, 2018a; Liao et al, 2018b)
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