Glycolipid transfer protein (GLTP) is a monomeric, soluble protein that can mediate the intermembrane transport of glycosphingolipids (GSLs) (Malinina et al. 2004, Malinina et al. 2006, Tuuf & Mattjus 2007). GLTPs could serve as potential regulators of cell processes mediated by GSLs such as differentiation and proliferation to invasive adhesion, neurodegeneration and apoptosis. This reaction shows one example of GSL transfer from the plasma membrane to ER membrane.