The glycoproteins of the Old World arenaviruses LASV and LCMV were the first viral glycoproteins that were shown to be proteolytically processed by S1P [23, 26] , which normally plays important physiological regulatory roles in cholesterol metabolism, ER stress response, cartilage development and other cellular processes [21, 27, 28, 29, 30, 31] . Using systematic mutational analysis of the LCMV GP cleavage site, the consensus motif R-(R/K/ H)-L-(A/L/S/T/F) was determined, which is conserved in the glycoprotein sequences of the Old World viruses LASV, Mopeia and Mobala, as well as the New World virus Pichinde, suggesting that all arenavirus glycoproteins are cleaved by S1P [26, 32] . Indeed, more recently Rojek et al. reported that glycoproteins from the New World hemorrhagic fever viruses Junin, Machupo and Guanarito are also processed by S1P, although Guanarito possesses a protease recognition motif that differs from known arenavirus GP consensus cleavage sequences, indicating a broader substrate specificity of S1P than previously anticipated [33] .