Trans-Cellular Mobility of GPI-Anchored Proteins
Pp. 19-33 (15)
Barbara Viljetic, Marija Heffer-Lauc and Gordan Lauc
Glycosylphosphatidylinositol (GPI)-anchored proteins are comprised of a relatively large hydrophilic
moiety tethered to a membrane by a relatively small lipid tail. The functional role of the anchor is not clearly
established, and proposals range from cell motility to cell signaling. Together with gangliosides and cholesterol,
GPI-anchored proteins form membrane microdomains called lipid rafts in the outer leaflet of the plasma
membrane that are involved in the regulation and modulation of numerous cellular processes.
GPI-anchored proteins can be actively shed from the membrane of one cell and taken up by other cells by
insertion of their lipid anchors into the cell membrane. There are physiological processes where trans-cellular
mobility of GPI-anchored proteins occurs. This process appears to be regulated, and most probably involves
catalytic activity of some proteins that still have to be identified (GPI-specific phospholipases). Tumor cells and
some pathogens apparently misuse this process for their own advantage, but its real physiological functions
remain to be discovered. Special attention should be given when using detergents for biochemical and
immunohistochemical methods in analysis of these molecules because of probable artifacts.