Lola A. Brown 1 , Cassiah Cox 1 , Janae Baptiste 1 , Holly Summers 1 , Ryan Button 1 , Kennedy Bahlow 1 , Vaughn Spurrier 1 , Jenna Kyser 1 , Benjamin G. Luttge 2 , Lillian Kuo 2 , Eric O. Freed 2 , * , Michael F. Summers 1 , *
30 April 2015
Membrane targeting by the Gag proteins of the human immunodeficiency viruses (HIV types-1 and -2) is mediated by Gag’s N-terminally myristylated matrix (MA) domain and is dependent on cellular phosphatidylinositol-4,5-bisphosphate [PI(4,5)P 2]. To determine if other lentiviruses employ a similar membrane targeting mechanism, we initiated studies of the feline immunodeficiency virus (FIV), a widespread feline pathogen with potential utility for development of human therapeutics. Bacterial co-translational myristylation was facilitated by mutation of two amino acids near the amino-terminus of the protein (Q5A/G6S; myrMA Q5A/G6S). These substitutions did not affect virus assembly or release from transfected cells. NMR studies revealed that the myristyl group is buried within a hydrophobic pocket in a manner that is structurally similar to that observed for the myristylated HIV-1 protein. Comparisons with a recent crystal structure of the unmyristylated FIV protein [myr(-)MA] indicate that only small changes in helix orientation are required to accommodate the sequestered myr group. Depletion of PI(4,5)P 2 from the plasma membrane of FIV-infected CRFK cells inhibited production of FIV particles, indicating that, like HIV, FIV hijacks the PI(4,5)P 2 cellular signaling system to direct intracellular Gag trafficking during virus assembly.