StarD7 is a fusogenic protein that binds cardiolipin and phosphatidylserine

ANGELETTI SOFÍA; CHEN Q; CHAMLEY L; RENA VIVIANA; PANZETTA-DUTARI GRACIELA; GENTI-RAIMONDI SUSANA

San Miguel de Tucumán, Tucumán

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2009

SAIB

StarD7 is a novel protein of unknown function that belongs to the START lipid domain family. It was previously found that StarD7 is able to interact in lipid monolayers with phosphatidylserine (PS). Moreover, StarD7 is partially relocated from the cytoplasm to the plasma membrane during in vitro cytotrophoblast differentiation into syncytiotrophoblast (STB), a process characterized by an enrichment of PS into the STB surface. This study further investigates the function of StarD7 in trophoblasts. Here we demonstrate an inhibition of BeWo cell proliferation by incubation with recombinant StarD7 at 5, 10 and 20 mg/ml. Fluorescent microscopy indicated that there were few intercellular desmosomes between adjacent BeWo cells after treatment with StarD7 at 20 mg/ml. Similar results were found in control cultures treated with 5 mM forskolin. In addition, a protein-lipid overlay assay was performed by an ELISA method using cardiolipin (CL), PS, cholesterol (Chol), ceramide (Cer) and phosphatidylinosytol (PI). The results indicate that StarD7 binds CL and PS, but no PI, Chol or Cer. Altogether, these findings and previous data indicate that StarD7 is a fusogenic protein leading us to conclude that StarD7 can initiate/facilitate the syncytialization of BeWo cells through transport of PS to the STB membrane surface. Supported by SACyT, MinCyT of Córdoba, CONICET, FONCyT and SECyT-UNC