At the endoplasmic reticulum (ER) membrane, phosphatidylinositol 4-kinase alpha (PI4KA) (Wong et al. 1997, Gehrmann et al. 1999) or phosphatidylinositol 4-kinase type 2-beta (PI4K2B) (Wei et al. 2002) phosphorylate phosphatidylinositol (PI) to produce phosphatidylinositol 4-phosphate (PI4P).
At the Golgi membrane, phosphatidylinositol 4-kinase alpha (PI4KA) (Gehrmann et al. 1999, Godi et al. 1999), or phosphatidylinositol 4-kinase type 2-alpha/beta (PI4K2A/B) (Balla et al. 2002, Minogue et al. 2001, Wei et al. 2002) phosphorylate phosphatidylinositol (PI) to produce phosphatidylinositol 4-phosphate (PI4P).