Design and synthesis of lipid-coupled inositol 1,2,3,4,5,6-hexakisphosphate derivatives exhibiting high-affinity binding for the HIV-1 MA domain

Abstract

The precursor of Gag protein (Pr55^Gag) of human immunodeficiency virus, the principal structural component required for virus assembly, is known to bind D-myo-phosphatidylinositol 4,5-bisphosphate (PIP₂). The N-terminus of Pr55^Gag, the MA domain, plays a critical role in the binding of Pr55^Gag to the plasma membrane. Herein, we designed and synthesized myo-phosphatidylinositol 2,3,4,5,6-pentakisphosphate (PIP₅) derivatives comprising highly phosphorylated inositol and variously modified diacylglycerol to examine the MA-binding properties. The inositol moiety was synthesized starting with myo-inositol and assembled with a hydrophobic glycerol moiety through a phosphate linkage. The K_d value for MA-binding of the PIP₅ derivative 2 (K_d = 0.25 μM) was the lowest (i.e., highest affinity) of all derivatives, i.e., 70-fold lower than the K_d for the PIP₂ derivative 1 (K_d = 16.9 μM) and 100-fold lower than the K_d for IP₆ (K_d = 25.7 μM), suggesting the possibility that the PIP₅ derivative blocks Pr55^Gag membrane binding by competing with PIP₂ in MA-binding.