Cleavage of Peptides from Amphibian Skin Revealed by Combining Analysis of Gland Secretion and in Situ MALDI Imaging Mass Spectrometry

Abstract

Peptides from skin secretions of amphibians are considered important components of their immune system and also play a relevant role in their defense mechanism against predators. Herein, by using mass spectrometry (MS), we characterize the sequence of 13 peptides from the gland secretion of the hylid tree frog, Boana punctata. Using in situ matrix-assisted laser desorption ionization imaging MS of a transverse section of the skin tissue, we show that some peptides are stored as longer molecules that are cleaved after being secreted, whereas others do not undergo any modification. Sequence comparison with peptides from other Boana species and analysis of the three-dimensional theoretical structure indicate that this cleavage depends on both the presence of a specific sequence motif and the secondary structure. The fact that peptides undergo a rapid cleavage upon secretion suggests that stored and secreted peptides may have distinct roles for anuran survival, including defense against pathogens and predators.

Novel Ocellatin Peptides Mitigate LPS-induced ROS Formation and NF-kB Activation in Microglia and Hippocampal Neurons

“…9A). After 30 minutes of incubation with Ocellatin-K1 (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16), no significant morphological changes in the cells were found at the concentrations tested (250, 500 and 1000 µg/mL; Fig. 9B-F, respectively).…”

“…Ocellatin-K1(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) and Ocellatin-K1(1-21) protect hippocampal neurons from oxidative stress induced by LPS-treated-microglial conditioned media. Representative confocal images and quantification of ROS production in hippocampal neurons incubated with conditioned medium from microglia subjected to LPS-induced and 100 μM Ocellatin-K1(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) or Ocellatin-K1(1-21). Images show neurons expressing mVenus (green) and the Hyper Red ROS biosensor (red).…”

Drug Discovery on Natural Products: From Ion Channels to nAChRs, from Nature to Libraries, from Analytics to Assays

“…This information can be valuable toward unraveling information on peptide function and mechanism of action, as some of these peptides show neuroactive and antimicrobial activities. 191 MALDI imaging-MS can also be used for neurotransmitter distribution visualization/mapping of brain tissue, specifically focused on ACh 192 and reviewed by Romero-Perez et al (2015). 193 Several studies have suggested that using MALDI-MS/MS and ESI-MS/MS in parallel for the study of venomics gives rise to complementary mass spectral data of venom compounds and therewith a more complete view of the venom profile.…”

Use of whole‐body cryosectioning and desorption electrospray ionization mass spectrometry imaging to visualize alkaloid distribution in poison frogs

“…The production, storage, and mechanism of secretions have been studied extensively, and the biochemical pathways and distribution of these compounds are known for some amphibian species. Barbosa et al 8 and Brunetti et al 9 used matrix‐assisted laser desorption ionization (MALDI)‐MSI in studies of peptide distribution in the skin of two different frog species. Although MALDI‐MSI is one of the most commonly used methods of mass spectrometry for ex vivo molecular viewing of targeted organs or whole‐body sections from an animal, 10,11 its reliance on a ultraviolet (UV)‐absorbing matrix to ionize molecules can hinder the detection of small molecules.…”