Department of Chemistry and Biochemistry, University of Windsor, Windsor N9B 3P4, ON, Canada.
Department of Pharmacology, University of Virginia, Charlottesville 22908, VA, USA.
Chem Phys Lipids. 2022 Jul;245:105205. doi: 10.1016/j.chemphyslip.2022.105205. Epub 2022 Apr 26.
Ceramides and diacylglycerols are groups of lipids capable of nucleating and stabilizing ordered lipid domains, structures that have been implicated in a range of biological processes. Previous studies have used fluorescence reporter molecules to explore the influence of ceramide acyl chain structure on sphingolipid-rich ordered phases. Here, we use small-angle neutron scattering (SANS) to examine the ability of ceramides and diacylglycerols to promote lipid domain formation in the well-characterized domain-forming mixture DPPC/DOPC/cholesterol. SANS is a powerful, probe-free technique for interrogating membrane heterogeneity, as it is differentially sensitive to hydrogen's stable isotopes protium and deuterium. Specifically, neutron contrast is generated through selective deuteration of lipid species, thus enabling the detection of nanoscopic domains enriched in deuterated saturated lipids dispersed in a matrix of protiated unsaturated lipids. Using large unilamellar vesicles, we found that upon replacing 10 mol% DPPC with either C16:0 or C18:0 ceramide, or 16:0 diacylglycerol (dag), lipid domains persisted to higher temperatures. However, when DPPC was replaced with short chain (C6:0 or C12:0) or very long chain (C24:0) ceramides, or ceramides with unsaturated acyl chains of any length (C6:1(3), C6:1(5), C18:1, and C24:1), as well as C18:1-dag, lipid domains were destabilized, melting at lower temperatures than those in the DPPC/DOPC/cholesterol system. These results show how ceramide acyl chain length and unsaturation influence lipid domains and have implications for how cell membranes might modify their function through the generation of different ceramide species.
神经酰胺和二酰基甘油是能够成核和稳定有序脂质结构域的脂质群，这些结构域与多种生物过程有关。先前的研究使用荧光报告分子来研究神经酰胺酰链结构对富含神经鞘脂的有序相的影响。在这里，我们使用小角中子散射（SANS）来研究神经酰胺和二酰基甘油在特征明确的形成域混合物 DPPC/DOPC/胆固醇中促进脂质域形成的能力。SANS 是一种强大的、无探针技术，用于研究膜异质性，因为它对氢的稳定同位素氘和氕具有不同的敏感性。具体来说，通过对脂质物种进行选择性氘化产生中子对比，从而能够检测富含氘化饱和脂质的纳米级域，这些域分散在富含氕的不饱和脂质基质中。使用大单室囊泡，我们发现，当用 C16:0 或 C18:0 神经酰胺或 16:0 二酰基甘油（dag）替代 10 mol% DPPC 时，脂质域在更高温度下仍然存在。然而，当 DPPC 被短链（C6:0 或 C12:0）或非常长链（C24:0）神经酰胺或具有任何长度的不饱和酰链（C6:1(3)、C6:1(5)、C18:1 和 C24:1），以及 C18:1-dag 取代时，脂质域被破坏，在比 DPPC/DOPC/胆固醇体系更低的温度下融化。这些结果表明神经酰胺酰链长度和不饱和性如何影响脂质域，以及细胞膜如何通过产生不同的神经酰胺物种来改变其功能。
