Rabies virus-induced membrane fusion

Rabies virus is a member of the rhabdovirus family. It enters cells by a pr ocess of receptor mediated endocytosis, Following this step, the viral enve lope fuses with the endosomal membrane to allow release of the viral nucleo capsid into the cytoplasm, Fusion is induced by the low pH of the endosomal compartment and is mediated by the single viral glycoprotein G, a homotrim eric integral membrane protein. Fables virus fusion properties are related to different conformational states of G, By different biochemical and bioph ysical approaches, it has been demonstrated that G can assume at least thre e different states: the native (N) state detected at the viral surface abov e pH 7, the activated (A) hydrophobic state which interacts with the target membrane as a first step of the fusion process, and the fusion inactive (I ) conformation. Differently from other fusogenic viruses for which low pH-i nduced conformational changes are irreversible, there is a pH dependent equ ilibrium between these states, the equilibrium being shifted toward the I-s tate at low pH. The objective of this review is to detail recent findings o n rhabdovirus-induced membrane fusion and to underline the differences that exist between this viral family and influenza virus which is the best know n fusogenic virus. These differences have to be taken into consideration if one wants to have a global understanding of virus-induced membrane fusion.