Quantification of lipid sorting during clathrin-mediated endocytosis

Abstract

Clathrin-mediated endocytosis is a major transport route for proteins from the plasma membrane to the interior of the cell. While the recruitment of cargo proteins to clathrin-coated pits is well understood, it remains an open question whether lipids are also sorted by this process. Here, to address this question, we combined super-resolution stimulated emission depletion imaging of bifunctional lipid probes with mathematical modelling. Quantification of ten different lipid species revealed significant differences in pit partitioning, ranging from slight enrichment to moderate exclusion. We find that the lipid asymmetry in the plasma membrane is sufficient to explain the observed trend. Taken together, our findings imply that clathrin-mediated endocytosis has a minor selectivity for cytoplasmic leaflet lipids, but overall does not substantially contribute to lipid sorting compared with non-vesicular trafficking. Lennartz et al. evaluate lipid enrichment in clathrin-coated pits and observe that the differential lipid partitioning into clathrin-coated pits is largely driven by the lipid asymmetry of the plasma membrane.