title: A novel protein from the serum of Python sebae, structurally homologous with type-γ phospholipase A(2) inhibitor, displays antitumour activity.
abstract: Cytotoxic and antitumour factors have been documented in the venom of snakes, although little information is available on the identification of cytotoxic products in snake serum. In the present study, we purified and characterized a new cytotoxic factor from serum of the non-venomous African rock python (Python sebae), endowed with antitumour activity. PSS (P. sebae serum) exerted a cytotoxic activity and reduced dose-dependently the viability of several different tumour cell lines. In a model of human squamous cell carcinoma xenograft (A431), subcutaneous injection of PSS in proximity of the tumour mass reduced the tumour volume by 20%. Fractionation of PSS by ion-exchange chromatography yielded an active protein fraction, F5, which significantly reduced tumour cell viability in vitro and, strikingly, tumour growth in vivo. F5 is composed of P1 (peak 1) and P2 subunits interacting in a 1:1 stoichiometric ratio to form a heterotetramer in equilibrium with a hexameric form, which retained biological activity only when assembled. The two peptides share sequence similarity with PIP {PLI-γ [type-γ PLA(2) (phospholipase A(2)) inhibitor] from Python reticulatus}, existing as a homohexamer. More importantly, although PIP inhibits the hydrolytic activity of PLA(2), the anti-PLA(2) function of F5 is negligible. Using high-resolution MS, we covered 87 and 97% of the sequences of P1 and P2 respectively. In conclusion, in the present study we have identified and thoroughly characterized a novel protein displaying high sequence similarity to PLI-γ and possessing remarkable cytotoxic and antitumour effects that can be exploited for potential pharmacological applications.
authors.affiliation: Department of Biotechnology and Istituto Toscano Tumori, University of Siena, Via A. Moro 2, 53100 Siena, Italy.
authors.forename: Sandra
authors.initials: S
authors.lastname: Donnini
authors.forename: Federica
authors.initials: F
authors.lastname: Finetti
authors.forename: Simona
authors.initials: S
authors.lastname: Francese
authors.forename: Francesca
authors.initials: F
authors.lastname: Boscaro
authors.forename: Francesca R
authors.initials: FR
authors.lastname: Dani
authors.forename: Fabio
authors.initials: F
authors.lastname: Maset
authors.forename: Roberta
authors.initials: R
authors.lastname: Frasson
authors.forename: Michele
authors.initials: M
authors.lastname: Palmieri
authors.forename: Mario
authors.initials: M
authors.lastname: Pazzagli
authors.forename: Vincenzo
authors.initials: V
authors.lastname: De Filippis
authors.forename: Enrico
authors.initials: E
authors.lastname: Garaci
authors.forename: Marina
authors.initials: M
authors.lastname: Ziche
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000970:Antineoplastic Agents / Q000097:blood / Q000302:isolation & purification*; D017209:Apoptosis / Q000187:drug effects; D017821:Boidae / Q000097:blood; D001943:Breast Neoplasms / Q000188:drug therapy; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000097:blood* / Q000302:isolation & purification / Q000494:pharmacology; D005260:Female; D005909:Glioblastoma / Q000188:drug therapy; D054513:Group IV Phospholipases A2 / Q000037:antagonists & inhibitors*; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy; D051379:Mice; D008969:Molecular Sequence Data; D010741:Phospholipases A / Q000037:antagonists & inhibitors; D011506:Proteins / Q000302:isolation & purification / Q000494:pharmacology; D016415:Sequence Alignment
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D011506:Proteins; D010741:Phospholipases A; D054513:Group IV Phospholipases A2