title: Tachyplesin activates the classic complement pathway to kill tumor cells.
abstract: Tachyplesin is a small, cationic peptide that possesses antitumor properties. However, little is known about its action mechanism. We used phage display to identify a protein that interacted with tachyplesin and isolated a sequence corresponding to the collagen-like domain of C1q, a key component in the complement pathway. Their interaction was subsequently confirmed by both ELISA and affinity precipitation. Tachyplesin seemed to activate the classic complement cascade because it triggered several downstream events, including the cleavage and deposition of C4 and C3 and the formation of C5b-9. When TSU tumor cells were treated with tachyplesin in the presence of serum, activated C4b and C3b could be detected on tumor cells by flow cytometry, Western blotting, and confocal microscopy. However, this effect was blocked when the tumor cells were treated with hyaluronidase or a large excess of hyaluronan, indicating that hyaluronan or related glycosaminoglycans were involved in this process. Treatment of cells with tachyplesin and serum increased in membrane permeability as indicated by the ability of FITC-dextran to enter the cytoplasm. Finally, the combination of tachyplesin and human serum markedly inhibited the proliferation and caused death of TSU cells, and these effects were attenuated if the serum was heat-inactivated or if hyaluronidase was added. Taken together, these observations suggest that tachyplesin binds to both hyaluronan on the cell surface and C1q in the serum and activates the classic complement cascade, which damages the integrity of the membranes of the tumor cells resulting in their death.
authors.affiliation: Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia, USA.
authors.forename: Jinguo
authors.initials: J
authors.lastname: Chen
authors.forename: Xue-Ming
authors.initials: XM
authors.lastname: Xu
authors.forename: Charles B
authors.initials: CB
authors.lastname: Underhill
authors.forename: Shanmin
authors.initials: S
authors.lastname: Yang
authors.forename: Luping
authors.initials: L
authors.lastname: Wang
authors.forename: Yixin
authors.initials: Y
authors.lastname: Chen
authors.forename: Shuigen
authors.initials: S
authors.lastname: Hong
authors.forename: Karen
authors.initials: K
authors.lastname: Creswell
authors.forename: Lurong
authors.initials: L
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D023181:Antimicrobial Cationic Peptides / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D045744:Cell Line, Tumor; D015922:Complement C1q / Q000378:metabolism; D003179:Complement C3b / Q000276:immunology / Q000378:metabolism; D015935:Complement C4b / Q000276:immunology / Q000378:metabolism; D003171:Complement Pathway, Classical / Q000187:drug effects*; D004268:DNA-Binding Proteins / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D006820:Hyaluronic Acid / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D019151:Peptide Library; D010456:Peptides, Cyclic / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism
chemical_list: D023181:Antimicrobial Cationic Peptides; D004268:DNA-Binding Proteins; D019151:Peptide Library; D010456:Peptides, Cyclic; C057636:tachyplesin peptide, Tachypleus tridentatus; D015922:Complement C1q; D003179:Complement C3b; D015935:Complement C4b; D006820:Hyaluronic Acid