Antimicrobial, cytotoxic, and insulin-releasing activities of the amphibian host-defense peptide ocellatin-3N and its L-lysine-substituted analogs

J. Michael Conlon, Lauren Hunter, Samir Attoub, Bruno Casciaro, Milena Mechkarska, Yasser H.A. Abdel-Wahab

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


The host-defense peptide ocellatin-3N (GIFDVLKNLAKGVITSLAS.NH2), first isolated from the Caribbean frog Leptodactylus nesiotus, inhibited growth of clinically relevant Gram-positive and Gram-negative bacteria as well as a strain of the major emerging yeast pathogen Candida parapsilosis. Increasing cationicity while maintaining amphipathicity by the substitution Asp4→Lys increased potency against the microorganisms by between 4- and 16-fold (MIC ≤3 μM) compared with the naturally occurring peptide. The substitution Ala18→Lys and the double substitution Asp4→Lys and Ala18→Lys had less effects on potency. The [D4K] analog also showed 2.5- to 4-fold greater cytotoxic potency against non-small-cell lung adenocarcinoma A549 cells, breast adenocarcinoma MDA-MB-231 cells, and colorectal adenocarcinoma HT-29 cells (LC50 values in the range of 12–20 μM) compared with ocellatin-3N but was less hemolytic to mouse erythrocytes. However, the peptide showed no selectivity for tumor-derived cells [LC50 = 20 μM for human umbilical vein endothelial cells (HUVECs)]. Ocellatin-3N and [D4K]ocellatin-3N stimulated the release of insulin from BRIN-BD11 clonal β-cells at concentrations ≥1 nM, and [A18K]ocellatin-3N, at concentrations ≥0.1 nM. No peptide stimulated the release of lactate dehydrogenase at concentrations up to 3 μM, indicating that plasma membrane integrity had been preserved. The three peptides produced an increase in intracellular [Ca2+] in BRIN-BD11 cells when incubated at a concentration of 1 μM. In view of its high insulinotropic potency and relatively low hemolytic activity, the [A18K] ocellatin analog may represent a template for the design of agents with therapeutic potential for the treatment of patients with type 2 diabetes.

Original languageEnglish
Article numbere3463
JournalJournal of Peptide Science
Issue number4
Publication statusPublished - Apr 2023


  • Leptodactylidae
  • antimicrobial peptide
  • cytotoxicity
  • diabetes
  • frog skin
  • insulin release

ASJC Scopus subject areas

  • Structural Biology
  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Pharmacology
  • Drug Discovery
  • Organic Chemistry


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