A New Family of Diverse Skin Peptides from the Microhylid Frog Genus Phrynomantis

Abstract

A wide range of frogs produce skin poisons composed of bioactive peptides for defence against pathogens, parasites and predators. While several frog families have been thoroughly screened for skin-secreted peptides, others, like the Microhylidae, have remained mostly unexplored. Previous studies of microhylids found no evidence of peptide secretion, suggesting that this defence adaptation was evolutionarily lost. We conducted transcriptome analyses of the skins of Phrynomantis bifasciatus and Phrynomantis microps, two African microhylid species long suspected to be poisonous. Our analyses reveal 17 evolutionary related transcripts that diversified from to those of cytolytic peptides found in other frog families. The 19 peptides predicted to be processed from these transcripts, named phrynomantins, show a striking structural diversity that is distinct from any previously identified frog skin peptide. Functional analyses of five phrynomantins confirm the loss of a cytolytic function and the absence of insecticidal or proinflammatory activity, suggesting that they represent an evolutionary transition to a new, yet unknown function. Our study shows that peptides have been retained in the defence poison of at least one microhylid lineage and encourages research on similarly understudied taxa to further elucidate the diversity and evolution of skin defence molecules.

Toxicity Evaluation of Anti‐cholinesterasic Amphibian Extracts by MTT and an Optimized Artemia salina Test

“…Amphibian skin secretions are known to contain alkaloids, biogenic amines, steroids and hundreds of species‐specific peptides and proteins [5,31] . In this sense, there are numerous reports about bioactive peptides isolated from amphibian species belonging to Hylidae, Microhylidae and Leptodactylidae families [9,32,33] …”

“…[5,31] In this sense, there are numerous reports about bioactive peptides isolated from amphibian species belonging to Hylidae, Microhylidae and Leptodactylidae families. [9,32,33] The nine amphibian skin extracts here studied were formerly obtained and chemically characterized in a previous work conducted by Spinelli et al [34] In this regard, the analytical characterization of Hylidae, Microhylidae, and Leptodactylidae extracts showed varying protein content. Hylidae and Microhylidae exhibited higher protein percentages (29.08 to 64.38 %) than Leptodactylidae (up to 39.22 %).…”

Manual mass spectrometry de novo sequencing of the anionic host defense peptides of the Cuban Treefrog Osteopilus septentrionalis

“…Mass spectrometry screening to detect peptides with the structures predicted by preliminary cDNA cloning may be an efficient approach. However, the amphibian peptidome is usually smaller than the transcryptome due to possible rapid peptide degradation upon secretion and uncorrelated temporal variation in transcription and peptide synthesis, 43 demonstrating at the same time a number of post‐translational modifications in the structure of the secreted peptides. The most efficient approach so far involves recording and manual interpretation of complementary ECD/ETD, CID, and HCD spectra preferably with accurate mass measurements 37–39,44–46 …”

First Bioprospecting Study of Skin Host-Defense Peptides in Odontophrynus americanus

“…Since the pioneering studies by the Erspamer group, it has been well-established that anuran skin secretion harbors a diverse array of compounds, exhibiting a wide spectrum of biological activity. − Among these compounds are host defense peptides (HDPs), known for their capability to inhibit bacterial growth and demonstrating remarkable diversity in their bioactivity spectrum against a wide range of microorganisms. − These molecules hold significant potential for drug development. , …”