title: Interferon-gamma activity is potentiated by an intracellular peptide derived from the human 19S ATPase regulatory subunit 4 of the proteasome.
abstract: Hundreds of intracellular peptides that are neither antigens nor neuropeptides are present in mammalian cells and tissues. These peptides correspond to fragments of cytosolic, nuclear or mitochondrial proteins. Proteasome inhibition affects the levels of the intracellular peptides in human cell lines. Here, the effect of immuneproteasome expression on the intracellular peptide profile was evaluated, and its functional significance was investigated. The expression of the immuneproteasome in HeLa cells was induced by interferon gamma treatment, and the relative concentrations of the intracellular peptides were compared to those of the control cells using isotope labeling and electron spray mass spectrometry. One of the peptides identified, VGSELIQKY (EL28), corresponds to amino acids 251-259 of the human 19S ATPase regulatory subunit 4. This peptide was increased in the extracts of HeLa cells that had been treated with interferon gamma compared to those of control cells. In vitro, EL28 increased the chymotrypsin, trypsin and caspase-like proteasome activities. In vivo, when covalently linked to a cell-penetrating peptide, EL28 potentiated the ability of interferon gamma to stimulate the expression of the immuneproteasome β5i subunit and to increase the proliferation of CD8+ T-cells. The EL28/cell-penetrating peptide construct also improved and positively modulated the secondary IgG anti-bovine serum albumin immune responsiveness elicited in high antibody-responder mice. Together, these results suggest that EL28 is a functional intracellular peptide that can potentiate interferon gamma activity.
  
  
  
  The functional identification of EL28 advances our understanding regarding the bioactive peptides generated by limited proteolysis within cells.
authors: Department of Pharmacology, Biomedical Science Institute, University of São Paulo, São Paulo, 05508-000, SP, Brazil.
authors: Elisabete R C
authors: ER
authors: Monte
authors: Department of Immunology, Biomedical Science Institute, University of São Paulo, São Paulo, 05508-000, SP, Brazil.
authors: Cristiano
authors: C
authors: Rossato
authors: Department of Pharmacology, Biomedical Science Institute, University of São Paulo, São Paulo, 05508-000, SP, Brazil.
authors: Ricardo Pariona
authors: RP
authors: Llanos
authors: Department of Pharmacology, Biomedical Science Institute, University of São Paulo, São Paulo, 05508-000, SP, Brazil.
authors: Lilian C
authors: LC
authors: Russo
authors: Department of Pharmacology, Biomedical Science Institute, University of São Paulo, São Paulo, 05508-000, SP, Brazil.
authors: Leandro M
authors: LM
authors: de Castro
authors: Institute of Chemistry, State University of Campinas, 13083-862, Campinas, SP, Brazil.
authors: Fábio C
authors: FC
authors: Gozzo
authors: Laboratory of Immunochemistry, Center of Toxins, Immune Response and Cell Signaling (CETICS), Butantan Institute, 05503-000, São Paulo, SP, Brazil.
authors: Christiane B
authors: CB
authors: de Araujo
authors: Department of Immunology, Biomedical Science Institute, University of São Paulo, São Paulo, 05508-000, SP, Brazil.
authors: Jean Pierre S
authors: JP
authors: Peron
authors: Laboratory of Immunochemistry, Center of Toxins, Immune Response and Cell Signaling (CETICS), Butantan Institute, 05503-000, São Paulo, SP, Brazil.
authors: Osvaldo Augusto
authors: OA
authors: Sant'Anna
authors: Department of Pharmacology, Biomedical Science Institute, University of São Paulo, São Paulo, 05508-000, SP, Brazil. Electronic address: eferro@usp.br.
authors: Emer S
authors: ES
authors: Ferro
authors: Special Laboratory of Applied Toxinology (LETA), Center of Toxins, Immune Response and Cell Signaling (CETICS), Butantan Institute, 05503-000, São Paulo, SP, Brazil. Electronic address: vrioli@butantan.gov.br.
authors: Vanessa
authors: V
authors: Rioli
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000276:immunology; D000595:Amino Acid Sequence; D006367:HeLa Cells; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D013058:Mass Spectrometry; D010455:Peptides / Q000032:analysis / Q000302:isolation & purification* / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000276:immunology; D059748:Proteolysis
chemical_list: D010455:Peptides; D007371:Interferon-gamma; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases
keywords: Immunology; Interferon; Intracellular peptides; Proteasome; Proteolysis