Review Intracellular Peptides in Cell Biology and Pharmacology Christiane B. de Araujo 1, Andrea S. Heimann 2, Ricardo A. Remer 3, Lilian C. Russo 4, Alison Colquhoun 5, Fábio L. Forti 4 and Emer S. Ferro 6,* 1 Special Laboratory of Cell Cycle, Center of Toxins, Immune Response and Cell Signaling - CeTICS, Butantan Institute, São Paulo SP 05503-900, Brazil;
[email protected] 2 Proteimax Biotecnologia LTDA, São Paulo SP 05581-001, Brazil;
[email protected] 3 Remer Consultores Ltda., São Paulo, SP 01411-001, Brazil;
[email protected] 4 Department of Biochemistry, Chemistry Institute, University of São Paulo 1111, São Paulo 05508-000, Brazil;
[email protected];
[email protected] 5 Department of Cell and Developmental Biology, University of São Paulo (USP), São Paulo 05508-000, Brazil;
[email protected] 6 Department of Pharmacology, Biomedical Sciences Institute, University of São Paulo (USP), São Paulo 05508-000, Brazil;
[email protected] * Correspondence:
[email protected]; Tel.: +551130917310 Received: 28 February 2019; Accepted: 12 April 2019; Published: 16 April 2019 Abstract: Intracellular peptides are produced by proteasomes following degradation of nuclear, cytosolic, and mitochondrial proteins, and can be further processed by additional peptidases generating a larger pool of peptides within cells. Thousands of intracellular peptides have been sequenced in plants, yeast, zebrafish, rodents, and in human cells and tissues. Relative levels of intracellular peptides undergo changes in human diseases and also when cells are stimulated, corroborating their biological function. However, only a few intracellular peptides have been pharmacologically characterized and their biological significance and mechanism of action remains elusive.