The phosphatidylinositol transfer protein beta isoform (PITPNB) bound to phosphatidylinositol (PI) complex transports from the endoplasmic reticulum (ER) membrane to the Golgi membrane, where phosphatidylcholine (PC) is exchanged for PI. PITPNB now in complex with PC transports back to the ER membrane where PI is now exchanged for PC, and the cycle repeats. This process has been characterized in detail in bovine and rodent model systems (e.g., Wirtz et al. 2006; Ghosh and Bankaitis 2011), which provide a framework for organizing the more limited data available for the very well conserved human proteins and processes( Carvou et al. 2010, Shadan et al. 2008).