Acyl and alkyl chain length of GPI-anchors is critical for raft association in vitro.

We determined the acyl and alkyl chain composition of GPI-anchors isolated from MDCK and Fischer rat thyroid (FRT) cells. Both cell lines synthesize GPI-anchors containing C16/C18 or C18/C18 saturated acyl and alkyl chains. The GPI-anchored placental alkaline phosphatase (PLAP) expressed in both cells is raft-associated and PLAP purified from FRT cells is raft-associated in vitro when reconstituted into liposomes containing raft lipids. In contrast, the GPI-anchored variant surface glycoprotein from Trypanosoma brucei which contains C14 acyl and alkyl chains shows no significant raft association after reconstitution in vitro. These data indicate that the acyl and alkyl chain composition of GPI-anchors determines raft association.