About twenty years ago, the functional lipid raft model of the plasma membrane was published. It took into account decades of research showing that cellular membranes are not just homogenous mixtures of lipids and proteins. Lateral anisotropy leads to assembly of membrane domains with specific lipid and protein composition regulating vesicular traffic, cell polarity, and cell signaling pathways in a plethora of biological processes. However, what appeared to be a clearly defined entity of clustered raft lipids and proteins became increasingly fluid over the years, and many of the fundamental questions about biogenesis and structure of lipid rafts remained unanswered. Experimental obstacles in visualizing lipids and their interactions hampered progress in understanding just how big rafts are, where and when they are formed, and with which proteins raft lipids interact. In recent years, we have begun to answer some of these questions and sphingolipids may take center stage in re-defining the meaning and functional significance of lipid rafts. In addition to the archetypical cholesterol-sphingomyelin raft with liquid ordered (Lo) phase and the liquid-disordered (Ld) non-raft regions of cellular membranes, a third type of microdomains termed ceramide-rich platforms (CRPs) with gel-like structure has been identified. CRPs are “ceramide rafts” that may offer some fresh view on the membrane mesostructure and answer several critical questions for our understanding of lipid rafts.

大约二十年前，质膜的功能性脂筏模型发表。它考虑了数十年的研究，表明细胞膜不仅仅是脂质和蛋白质的均质混合物。横向各向异性导致具有特定脂质和蛋白质成分的膜域组装，调节大量生物过程中的囊泡运输、细胞极性和细胞信号传导途径。然而，多年来，似乎是一个明确定义的簇状筏脂质和蛋白质实体变得越来越不稳定，并且有关脂质筏生物发生和结构的许多基本问题仍未得到解答。可视化脂质及其相互作用方面的实验障碍阻碍了理解筏有多大、它们形成的地点和时间以及筏脂质与哪些蛋白质相互作用的进展。近年来，我们已经开始回答其中一些问题，鞘脂可能在重新定义脂筏的含义和功能意义方面占据中心地位。除了具有液体有序 (Lo) 相的典型胆固醇-鞘磷脂筏和细胞膜的液体无序 (Ld) 非筏区域之外，第三种类型的微域被称为富含神经酰胺平台 (CRP)，具有凝胶状结构已被识别。 CRP 是“神经酰胺筏”，它可以为膜介观结构提供一些新的视角，并回答我们理解脂筏的几个关键问题。