Impact of sphingomyelin acyl chain heterogeneity upon properties of raft-like membranes

• Published in: Biochimica et biophysica acta. Biomembranes 2022-12, Vol.1864 (12), p.184036-184036, Article 184036
• Main Authors: Hirano, Kana, Kinoshita, Masanao, Matsumori, Nobuaki
• Format: Article
• Language: English
• Subjects: Fluorescence labeling; Giant unilamellar vesicles; Lipid rafts; Long acyl chain; Phase separation; Sphingomyelin
• ISSN: 0005-2736; 1879-2642
• DOI: 10.1016/j.bbamem.2022.184036

Sphingomyelin (SM) is a main component of lipid rafts and characteristic of abundance of long and saturated acyl chains. Recently, we reported that fluorescence-labeled lipids including C16:0 and C18:0SMs retained membrane behaviors of inherent lipids. Here, we newly prepared fluorescent SMs with longer acyl chains, C22:0 and C24:1, for observing their partition and diffusion in SM/cholesterol (chol)/dioleoylphosphatidylcholine (DOPC) bilayers. Although fluorescent C24:1SM underwent a uniform distribution between ordered (Lo) and disordered (Ld) phases, other fluorescent SMs with saturated acyl chains were preferentially distributed in the Lo phase. Interestingly, when the acyl chains of fluorescent and membrane SMs are different, distribution of fluorescent SM to the Lo phase was reduced compared to when the acyl chains are the same. This tendency was also observed for C16:0SM/C22:0SM/chol/DOPC quaternary bilayers, where the minor SM was more excluded out of the Lo phase than the major SM. We also found that the coexistence of SMs induces SM efflux out of the Lo phase and simultaneous DOPC influx to the Lo phase, consequently reducing the difference in fluidity between the two phases. These results suggest that physicochemical properties of lipid rafts are regulated by the acyl chain heterogeneity of SMs. [Display omitted] •We newly prepared fluorescent SMs with long acyl chains, C22:0 and C24:1.•Lo partition of fluorescent SM is highest when its acyl chain matches membrane SM.•In C16:0SM/C22:0SM-mixed systems, the minor SM is more excluded from the Lo phase.•Mixing of C16:0SM/C22:0SM perturbs the Lo phase and allows influx of DOPC into it.•Heterogeneity of SM acyl chains might control membrane properties of lipid rafts.