Palmitoylation regulates raft affinity for the majority of integral raft proteins

TLDR

Protein partitioning into lipid rafts remains an unresolved question in membrane biology, previously addressed only with indirect detergent‑based methods. Using giant plasma membrane vesicles that phase‑separate into raft‑enriched ordered domains, the authors measured the partitioning of the T‑cell activation linker LAT. LAT enrichment in raft domains requires palmitoylation of two juxtamembrane cysteines and can be enhanced by oligomerization, a requirement that extends to most integral raft proteins and suggests that reversible palmitoylation functions as a dynamic raft‑targeting mechanism.

Abstract

The physical basis for protein partitioning into lipid rafts remains an outstanding question in membrane biology that has previously been addressed only through indirect techniques involving differential solubilization by nonionic detergents. We have used giant plasma membrane vesicles, a plasma membrane model system that phase separates to include an ordered phase enriching for raft constituents, to measure the partitioning of the transmembrane linker for activation of T cells (LAT). LAT enrichment in the raft phase was dependent on palmitoylation at two juxtamembrane cysteines and could be enhanced by oligomerization. This palmitoylation requirement was also shown to regulate raft phase association for the majority of integral raft proteins. Because cysteine palmitoylation is the only lipid modification that has been shown to be reversibly regulated, our data suggest a role for palmitoylation as a dynamic raft targeting mechanism for transmembrane proteins.