title: A Cyclin D2-derived peptide acts on specific cell cycle phases by activating ERK1/2 to cause the death of breast cancer cells.
abstract: Protein degradation by the proteasome generates functional intracellular peptides. Pep5, a peptide derived from Cyclin D2, induces cell death in tumor cell lines and reduces the volume of rat C6 glioblastoma tumors in vivo. Here, we chose the human MDA-MB-231 breast cancer cells to evaluate the mechanism of cell death induced by pep5 in different phases of the cell cycle. Fluorescently labeled pep5, monitored by real time confocal microscopy, entered the MDA-MB-231 cells 3min after application and localized to the nucleus and cytoplasm. Pep5-induced cell death was increased when the MDA-MB-231 cell population was arrested at the G1/S transition or in S phase compared to asynchronous cells. Pep5 induced permanent extracellular signal-regulated kinase (ERK1/2) phosphorylation in MDA-MB-231 cells synchronized in G1/S or S phase. Affinity chromatography followed by mass spectrometry identified CLIC1 and Plectin as the only two proteins that interacted with pep5 in both asynchronous and synchronized MDA-MB-231 cells. These interactions could explain the long-lasting ERK1/2 phosphorylation and the cytoskeleton perturbations in the MDA-MB-231 cells, in which the stress fibers' integrity is affected by pep5 treatments. These data suggest that pep5 has potential therapeutic properties for treating specific types of cancers, such as breast cancer cells.
  
  
  
  Pep5, a natural intracellular peptide formed by the degradation of Cyclin D2 through the ubiquitin-proteasome system, induces cell death when reintroduced into MDA-MB-231 breast cancer cells, which express low levels of Cyclin D2, specifically in G1/S arrested cells or in cells that are passing through S phase. Under these conditions, pep5 is able to interact with different intracellular proteins, primarily cytoskeleton and proteasome components, which can lead to cellular apoptosis. Together, our data suggest that pep5 is an intracellular peptide with therapeutic potential for treating specific types of tumors with low expression of Cyclin D2 by inhibiting cell proliferation.
authors.affiliation: Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, SP 05508-000, Brazil.
authors.forename: Lilian C
authors.initials: LC
authors.lastname: Russo
authors.affiliation: Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP 05508-000, Brazil; Special Laboratory of Applied Toxinology (LETA), Center of Toxins, Immune Response, and Cell Signaling (CETICS), Butantan Institute, São Paulo, SP 05503-000, Brazil.
authors.forename: Christiane B
authors.initials: CB
authors.lastname: Araujo
authors.affiliation: Special Laboratory of Applied Toxinology (LETA), Center of Toxins, Immune Response, and Cell Signaling (CETICS), Butantan Institute, São Paulo, SP 05503-000, Brazil.
authors.forename: Leo K
authors.initials: LK
authors.lastname: Iwai
authors.affiliation: Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP 05508-000, Brazil.
authors.forename: Emer S
authors.initials: ES
authors.lastname: Ferro
authors.affiliation: Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, SP 05508-000, Brazil. Electronic address: flforti@iq.usp.br.
authors.forename: Fabio L
authors.initials: FL
authors.lastname: Forti
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects*; D045744:Cell Line, Tumor; D018118:Chloride Channels / Q000378:metabolism; D056742:Cyclin D2 / Q000737:chemistry*; D003599:Cytoskeleton / Q000473:pathology; D005260:Female; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation; D051190:Plectin / Q000378:metabolism
chemical_list: C501966:CLIC1 protein, human; D018118:Chloride Channels; D056742:Cyclin D2; D010446:Peptide Fragments; D051190:Plectin
keywords: Breast cancer cells; Cell cycle; Cell death; Cyclin D2; ERK1/2 activation; Pep5