title: Skin secretion peptides: the molecular facet of the deimatic behavior of the four-eyed frog, Physalaemus nattereri (Anura, Leptodactylidae).
abstract: BACKGROUND
  Amphibians can produce a large amount of bioactive peptides over the skin. In order to map the precise tissue localization of these compounds and evaluate their functions, mass spectrometry imaging (MSI) and gene expression studies were used to investigate a possible correlation between molecules involved in the antimicrobial defense mechanisms and anti-predatory behavior by Physalaemus nattereri.
  
  
  METHODS
  Total skin secretion of P. nattereri was analyzed by classical Protein Chemistry and proteomic techniques. Intact inguinal macroglands were dissected from the rest of the skin and both tissues were analyzed by MSI and real-time polymerase chain reaction (RT-PCR) experiments. Peptides were primarily identified by de novo sequencing, automatic Edman degradation and cDNA data.
  
  
  RESULTS
  Fifteen bradykinin (BK)-related peptides and two antimicrobial peptides were sequenced and mapped by MSI on the inguinal macrogland and the rest of P. nattereri skin. RT-PCR results revealed that BK-related peptide levels of expression were about 30,000 times higher on the inguinal macroglands than on the any other region of the skin, whilst antimicrobial peptide ions appear to be evenly distributed in both investigated regions.
  
  
  CONCLUSIONS
  The presence of antimicrobial peptides in all investigated tissue regions is in accordance with the defensive role against microorganisms thoroughly demonstrated in the literature, whereas BK-related molecules are largely found on the inguinal macroglands suggesting an intriguing link between their noxious activities against potential predators of P. nattereri and the frog's deimatic behavior.
authors.affiliation: Embrapa Recursos Genéticos e Biotecnologia, Brasília-DF, Brazil.|Departamento de Biologia Celular, Universidade de Brasília, Brasília-DF, Brazil.
authors.forename: Eder Alves
authors.initials: EA
authors.lastname: Barbosa
authors.affiliation: Embrapa Recursos Genéticos e Biotecnologia, Brasília-DF, Brazil.|Faculdade Faceres, São José do Rio Preto-SP, Brazil.
authors.forename: Tatiane
authors.initials: T
authors.lastname: Iembo
authors.affiliation: Laboratório Sabin de Análises Clínicas, Brasília-DF, Brazil.
authors.forename: Graciella Ribeiro
authors.initials: GR
authors.lastname: Martins
authors.affiliation: Embrapa Recursos Genéticos e Biotecnologia, Brasília-DF, Brazil.
authors.forename: Luciano Paulino
authors.initials: LP
authors.lastname: Silva
authors.affiliation: Embrapa Recursos Genéticos e Biotecnologia, Brasília-DF, Brazil.
authors.forename: Maura Vianna
authors.initials: MV
authors.lastname: Prates
authors.affiliation: Embrapa Recursos Genéticos e Biotecnologia, Brasília-DF, Brazil.
authors.forename: Alan Carvalho
authors.initials: AC
authors.lastname: Andrade
authors.affiliation: Embrapa Recursos Genéticos e Biotecnologia, Brasília-DF, Brazil.
authors.forename: Carlos
authors.initials: C
authors.lastname: Bloch
mesh_terms: D000595:Amino Acid Sequence; D029845:Amphibian Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001001:Anura / Q000145:classification / Q000235:genetics / Q000502:physiology*; D001522:Behavior, Animal; D005260:Female; D008297:Male; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D040901:Proteomics; D012867:Skin / Q000737:chemistry* / Q000378:metabolism
chemical_list: D029845:Amphibian Proteins; D023181:Antimicrobial Cationic Peptides