How curved membranes recruit amphipathic helices and protein anchoring motifs

Abstract

Lipids and several specialized proteins are thought to be able to sense the curvature of membranes (MC). Here we used quantitative fluorescence microscopy to measure curvature-selective binding of amphipathic motifs on single liposomes 50-700 nm in diameter. Our results revealed that sensing is predominantly mediated by a higher density of binding sites on curved membranes instead of higher affinity. We proposed a model based on curvature-induced defects in lipid packing that related these findings to lipid sorting and accurately predicted the existence of a new ubiquitous class of curvature sensors: membrane-anchored proteins. The fact that unrelated structural motifs such as alpha-helices and alkyl chains sense MC led us to propose that MC sensing is a generic property of curved membranes rather than a property of the anchoring molecules. We therefore anticipate that MC will promote the redistribution of proteins that are anchored in membranes through other types of hydrophobic moieties.

A sub-nanometre view of how membrane curvature and composition modulate lipid packing and protein recruitment

“…Other membrane-binding proteins as well as amphiphilic compounds used in chemical biology might prefer deeper or shallower defects, depending on the amino acid composition of their hydrophobic moiety 35,44,47,48 . These variations, which are also critical in membrane curvature generation mechanisms 49 , are ignored in models where membrane curvature is assumed to simply increase the number of 'binding sites' for peripheral proteins, regardless of the type of hydrophobic moieties 16,17 . Therefore, our atomistic approach should be instrumental to better characterize various modes of protein adsorption on membrane organelles.…”

“…In turn, this stress triggers a response characterized by the upregulation of a fatty acid desaturase (Ole1 in yeast) and the arrest of cholesterol synthesis [9][10][11][12] . In addition, several peripheral proteins involved in various functions (lipid transfer, autophagy, nuclear pore formation, vesicle tethering and protein coat dynamics) seem to recognize lipid-packing defects by adsorbing preferentially to positively curved membranes through the insertion of long amphipathic sequences 4,[13][14][15][16][17] .…”

Ongoing activation of sphingosine 1-phosphate receptors mediates maturation of exosomal multivesicular endosomes

“…Recently, it has been reported that the bg subunits of G proteins can also sense membrane curvature 57 . The present studies from our laboratory have demonstrated an 'ongoing activation' of Gi-coupled S1P receptors that is necessary for cargo sorting into ILVs destined for exosomal release.…”

“…Exosomal content quantification assay was performed by fluorescence-based single liposome assay 57 . HeLa cells were seeded at 5 Â 10 5 cells on 60 mm culture dish and cells were transfected with CD63-GFP and indicated siRNAs.…”

Molecular basis for SH3 domain regulation of F-BAR–mediated membrane deformation

“…In most cases, dynamic membrane remodeling is accomplished by the reversible assembly of membrane-deforming proteins (1,2), most notably by members of the Bin/amphiphysin/Rvs (BAR) domain superfamily (3). BAR domains are characterized by α-helical coiled coils that dimerize into modules with a positively charged surface that interacts with phospholipid membranes (4,5).…”