Lipid‐matrix‐dependent effects of ceramide enrichment on cholesterol‐containing PSM and DLPC membranes

Abstract

Ceramide is a bioactive sphingolipid that can reorganize cholesterol‐containing membranes, but how membrane properties change with increasing ceramide content in different lipid matrices remains unclear. Using Martini 3 coarse‐grained molecular dynamics simulations, we examine cholesterol‐containing PSM and DLPC membranes across a controlled palmitoyl ceramide (PCER) composition series at a single liquid‐phase temperature. Increasing PCER fraction generally decreases area per lipid and increases lipid ordering, consistent with membrane condensation. However, the responses differ between matrices. In PSM/CHOL, PCER is accommodated within an already ordered environment, producing only modest membrane stiffening. In DLPC/CHOL, PCER leads to greater changes in local packing heterogeneity and lateral organization, accompanied by a nonmonotonic mechanical response. PCER enrichment also changes the positional and orientational distributions of cholesterol in a matrix‐dependent manner. These results show that ceramide‐induced condensation does not necessarily produce monotonic membrane stiffening and highlight the importance of the host lipid matrix in determining membrane structure and mechanics.