A Novel Intracellular Peptide Derived from G1/S Cyclin D2 Induces Cell Death

• Published in: The Journal of biological chemistry 2014-06, Vol.289 (24), p.16711-16726
• Main Authors: de Araujo, Christiane B., Russo, Lilian C., Castro, Leandro M., Forti, Fábio L., do Monte, Elisabete R., Rioli, Vanessa, Gozzo, Fabio C., Colquhoun, Alison, Ferro, Emer S.
• Format: Article
• Language: English
• Subjects: Amino Acid Chloromethyl Ketones - pharmacology; Amino Acid Motifs; Animals; Anticancer Drug; Antineoplastic Agents - chemistry; Antineoplastic Agents - pharmacology; Antineoplastic Agents - therapeutic use; Apoptosis; Apoptosis - drug effects; Apoptosis Regulatory Proteins - genetics; Apoptosis Regulatory Proteins - metabolism; Cell Cycle; Cell Death; Cyclin D2 - chemistry; Cyclin D2 - pharmacology; Enzymology; Glioblastoma - drug therapy; HeLa Cells; Humans; Imidazoles - pharmacology; Indoles - pharmacology; Male; Maleimides - pharmacology; MCF-7 Cells; Necrosis (Necrotic Death); Oligopeptides - chemistry; Oligopeptides - pharmacology; Oligopeptides - therapeutic use; Peptides; Proteasome; Quinolines - pharmacology; Rats; Rats, Wistar
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.537118

Intracellular peptides are constantly produced by the ubiquitin-proteasome system, and many are probably functional. Here, the peptide WELVVLGKL (pep5) from G1/S-specific cyclin D2 showed a 2-fold increase during the S phase of HeLa cell cycle. pep5 (25–100 μm) induced cell death in several tumor cells only when it was fused to a cell-penetrating peptide (pep5-cpp), suggesting its intracellular function. In vivo, pep5-cpp reduced the volume of the rat C6 glioblastoma by almost 50%. The tryptophan at the N terminus of pep5 is essential for its cell death activity, and N terminus acetylation reduced the potency of pep5-cpp. WELVVL is the minimal active sequence of pep5, whereas Leu-Ala substitutions totally abolished pep5 cell death activity. Findings from the initial characterization of the cell death/signaling mechanism of pep5 include caspase 3/7 and 9 activation, inhibition of Akt2 phosphorylation, activation of p38α and -γ, and inhibition of proteasome activity. Further pharmacological analyses suggest that pep5 can trigger cell death by distinctive pathways, which can be blocked by IM-54 or a combination of necrostatin-1 and q-VD-OPh. These data further support the biological and pharmacological potential of intracellular peptides. Background: Intracellular peptides probably regulate several biological processes. Results: pep5 derived from G1/S cyclin D2 specifically increases during the S phase of the cell cycle and, reintroduced into the cell, induces apoptosis and necrosis. Conclusion: pep5 has potential therapeutic applications and could have biological functions. Significance: pep5 discovery advances our understanding of limited proteolysis.