Early Steps of Jaagsiekte Sheep Retrovirus-Mediated Cell Transformation Involve the Interaction between Env and the RALBP1 Cellular Protein
Résumé
Ovine pulmonary adenocarcinoma is a naturally occurring lung cancer in sheep induced by the Jaagsiekte sheep retrovirus (JSRV). Its envelope glycoprotein (Env) carries oncogenic properties, and its expression is sufficient to induce in vitro cell transformation and in vivo lung adenocarcinoma. The identification of cellular partners of the JSRV envelope remains crucial for deciphering mechanisms leading to cell transformation. We initially identified RALBP1 (RalA binding protein 1; also known as RLIP76 or RIP), a cellular protein implicated in the ras pathway, as a partner of JSRV Env by yeast two-hybrid screening and confirmed formation of RALBP1/Env complexes in mammalian cells. Expression of the RALBP1 protein was repressed in tumoral lungs and in tumor-derived alveolar type II cells. Through its inhibition using specific small interfering RNA (siRNA), we showed that RALBP1 was involved in envelope-induced cell transformation and in modulation of the mTOR (mammalian target of rapamycin)/p70S6K pathway by the retroviral envelope. IMPORTANCE: JSRV-induced lung adenocarcinoma is of importance for the sheep industry. While the envelope has been reported as the oncogenic determinant of the virus, the cellular proteins directly interacting with Env are still not known. Our report on the formation of RALBP/Env complexes and the role of this interaction in cell transformation opens up a new hypothesis for the dysregulation observed upon virus infection in sheep.
Mots clés
Gene Expression Regulation
DNA Primers
Viral
Cell Transformation
Western
Open Reading Frames
Pulmonary Adenomatosis
Ovine
Multiprotein Complexes
Animals
ATP-Binding Cassette Transporters
Blotting
Neoplastic
Gene Products
env
GTPase-Activating Proteins
HEK293 Cells
Humans
Immunoprecipitation
Jaagsiekte sheep retrovirus
RNA
Small Interfering
Sheep
Sheep Diseases
Statistics
Nonparametric
Two-Hybrid System Techniques