PROTECTION AGAINST FATAL SINDBIS-VIRUS ENCEPHALITIS BY BECLIN, A NOVEL BCL-2-INTERACTING PROTEIN

bcl-2, the prototypic cellular antiapoptotic gene, decreases Sindbis v irus replication and Sindbis virus-induced apoptosis in mouse brains, resulting in protection against lethal encephalitis. To investigate po tential mechanisms by which Bcl-2 protects against central nervous sys tem Sindbis virus infection, we performed a yeast two-hybrid screen to identify Bcl-2-interacting gene products in an adult mouse brain libr ary. We identified a novel 60-kDa coiled-coil protein, Beelin, which w e confirmed interacts with Bcl-2 in mammalian cells, using fluorescenc e resonance energy transfer microscopy, To examine the role of Beclin in Sindbis virus pathogenesis, we constructed recombinant Sindbis viru s chimeras that express full-length human Beclin (SIN/beclin), Beclin lacking the putative Bcl-2-binding domain (SIN/beclin Delta Bcl-2BD), or Beclin containing a premature stop codon near the 5' terminus (SIN/ beclinstop). The survival of mice infected with SIN/beclin was signifi cantly higher (71%) than the survival of mice infected with SIN/beclin Delta Bcl-2BD (9%) or SIN/beclinstop (7%) (P < 0.001), The brains of mice infected with SIN/beclin had fewer Sindbis virus RNA-positive cel ls, fewer apoptotic cells, and lower viral titers than the brains of m ice infected with SIN/beclin Delta Bcl-2BD or SIN/beclinstop, These fi ndings demonstrate that Beclin is a novel Bcl-2-interacting cellular p rotein that may play a role in antiviral host defense.