Structural determinants and functional consequences of protein affinity for membrane rafts

Abstract

Eukaryotic plasma membranes are compartmentalized into functional lateral domains, including lipid-driven membrane rafts. Rafts are involved in most plasma membrane functions by selective recruitment and retention of specific proteins. However, the structural determinants of transmembrane protein partitioning to raft domains are not fully understood. Hypothesizing that protein transmembrane domains (TMDs) determine raft association, here we directly quantify raft affinity for dozens of TMDs. We identify three physical features that independently affect raft partitioning, namely TMD surface area, length, and palmitoylation. We rationalize these findings into a mechanistic, physical model that predicts raft affinity from the protein sequence. Application of these concepts to the human proteome reveals that plasma membrane proteins have higher raft affinity than those of intracellular membranes, consistent with raft-mediated plasma membrane sorting. Overall, our experimental observations and physical model establish general rules for raft partitioning of TMDs and support the central role of rafts in membrane traffic.

Imaging FCS Delineates Subtle Heterogeneity in Plasma Membranes of Resting Mast Cells

“…Lo-like nanodomains although palmitoylation, for example, may modulate these interactions (76). We monitor the TM receptor FcεRI as a complex with Alexafluor 488 labeled IgE (AF488-IgE-FcεRI; Figure 1B).…”

“…We tested AF488-IgE-FcεRI and other TM proteins with different numbers of TM segments and different preferences for Lo-like environments as evaluated by a variety of criteria (45,76). Not surprisingly, the Dav of these protein probes are substantially slower than the lipid-anchored probes, and those with a single TM segment (YFP-GL-GT46, EGFR-EGFP) diffuse somewhat faster than those with four (AcGFP-Orai1) or seven (AF488-IgE-FcεRI) TM segments.…”

Tuning of Differential Lipid Order Between Submicrometric Domains and Surrounding Membrane Upon Erythrocyte Reshaping

“…Accordingly, a recent study highlighted that lipid order differences arising from domain formation participate in selective sorting of membrane proteins [3]. This concept was first suggested in the 90's by the lipid raft hypothesis, which proposed that sterols and sphingolipids (SLs), due to their favorable interactions, can self-aggregate into rafts of higher lipid order as compared to the surrounding lipids (bulk), thereby mediating protein sorting and cellular functions.…”

Mixed Fluorinated/Hydrogenated Self‐Assembled Monolayer‐Protected Gold Nanoparticles: In Silico and In Vitro Behavior

“…We then moved toward more complex membrane models, in an attempt to reduce the gap between single‐component synthetic bilayers and real multicomponent cell membranes, by building a multicomponent raft‐like membrane model. Membrane rafts are thought to be implicated in key cellular processes, such as signaling, endocytosis, and adhesion …”