After the initial binding of the virion to the cell, L2 must be cleaved by the cellular protease furin.[67] The virion is internalized, probably through a clathrin-mediated process, into an endosome, where acidic conditions are thought to lead to exposure of membrane-destabilizing portions of L2.[3] The cellular proteins beta-actin[68] and syntaxin-18[69] may also participate in L2-mediated entry events.