title: Losac, a factor X activator from Lonomia obliqua bristle extract: its role in the pathophysiological mechanisms and cell survival.
abstract: Contact with the bristles of the caterpillar Lonomia obliqua can cause serious hemorrhage. Previously it was reported that a procoagulant protein (Lopap) in the bristle extract of L. obliqua increases cell longevity by inhibiting apoptosis. In this work, we purified from bristle extract a factor X activator that stimulates proliferation of endothelial cells. This protein, named Losac, was purified by ion exchange chromatography, followed by gel filtration chromatography and reverse-phase HPLC. Losac is a 45-kDa protein that activates factor X in a concentration-dependent manner and does not depend on calcium ions. In cultures of HUVECs, Losac increased cell proliferation and inhibited the apoptosis induced by starvation. HUVECs incubated with Losac (0.58microM for 1h) increased release of nitric oxide and tissue-plasminogen activator, which both may mediate anti-apoptosis. Losac also increased slightly the decay-accelerating factor (DAF=CD55), which protects cells from complement-mediated lysis. On the other hand, Losac did not alter the release or expression of von Willebrand factor, tissue factor, intercellular adhesion molecule-1, interleukin-8, and prostacyclin. These characteristics indicate that Losac, a protein with procoagulant activity, also functions as a growth stimulator and an inhibitor of cellular death for endothelial cells. Losac may have biotechnological applications, including the reduction of cell death and consequently increased productivity of animal cell cultures, and the use of hemolymph of L. obliqua for this purpose is already being explored. Further study is required to elucidate the mechanism for the inhibition of apoptosis by Losac.
authors.affiliation: Laboratório de Bioquímica e Biofísica, Instituto Butantan, São Paulo, Brazil.
authors.forename: Miryam Paola
authors.initials: MP
authors.lastname: Alvarez Flores
authors.forename: Márcio
authors.initials: M
authors.lastname: Fritzen
authors.forename: Cleyson V
authors.initials: CV
authors.lastname: Reis
authors.forename: Ana Marisa
authors.initials: AM
authors.lastname: Chudzinski-Tavassi
mesh_terms: D000825:Animal Structures / Q000737:chemistry; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011464:Epoprostenol / Q000378:metabolism; D006801:Humans; D019476:Insect Proteins / Q000494:pharmacology / Q000502:physiology*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D009036:Moths / Q000737:chemistry / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D013925:Thromboplastin / Q000378:metabolism; D014020:Tissue Extracts / Q000737:chemistry; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D019476:Insect Proteins; D016209:Interleukin-8; D009363:Neoplasm Proteins; D014020:Tissue Extracts; D014841:von Willebrand Factor; D018799:Intercellular Adhesion Molecule-1; D009569:Nitric Oxide; D013925:Thromboplastin; D011464:Epoprostenol; D003546:Cysteine Endopeptidases; C030910:cancer procoagulant