Plasma Membrane Phosphatidylinositol 4,5 Bisphosphate is Required for Internalization of Foot-and-mouth Disease Virus and Vesicular Stomatitis Virus

Phosphatidylinositol-4,5-bisphosphate, PI(4,5)P(2), is a phospholipid which plays important roles in clathrin-mediated endocytosis. To investigate the possible role of this lipid on viral entry, two viruses important for animal health were selected: the enveloped vesicular stomatitis virus (VSV) - which uses a well characterized clathrin mediated endocytic route - and two different variants of the non-enveloped foot-and-mouth disease virus (FMDV) with distinct receptor specificities. The expression of a dominant negative dynamin, a PI(4,5)P(2) effector protein, inhibited the internalization and infection of VSV and both FMDV isolates. Depletion of PI(4,5)P(2) from plasma membrane using ionomycin or an inducible system, and inhibition of its de novo synthesis with 1-butanol revealed that VSV as well as FMDV C-S8c1, which uses integrins as receptor, displayed a high dependence on PI(4,5)P(2) for internalization. Expression of a kinase dead mutant (KD) of phosphatidylinositol-4-phosphate-5-kinase Iα (PIP5K-Iα), an enzyme responsible for PI(4,5)P(2) synthesis that regulates clathrin-dependent endocytosis, also impaired entry and infection of VSV and FMDV C-S8c1. Interestingly FMDV MARLS variant that uses receptors other than integrins for cell entry was less sensitive to PI(4,5)P(2) depletion, and was not inhibited by the expression of the KD PIP5K-Iα mutant suggesting the involvement of endocytic routes other than the clathrin-mediated on its entry. These results highlight the role of PI(4,5)P(2) and PIP5K-Iα on clathrin-mediated viral entry.