Division of Gastroenterology, Boston Children's Hospital, Boston, MA 02115, USA.
Division of Rheumatology, Brigham and Women's Hospital, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA.
Cell Rep. 2022 Jul 12;40(2):111063. doi: 10.1016/j.celrep.2022.111063.
The complex sphingolipids exhibit a diversity of ceramide acyl chain structures that influence their trafficking and intracellular distributions, but it remains unclear how the cell discerns among the different ceramides to affect such sorting. To address the mechanism, we synthesize a library of GM1 glycosphingolipids with naturally varied acyl chains and quantitatively assess their sorting among different endocytic pathways. We find that a stretch of at least 14 saturated carbons extending from C1 at the water-bilayer interface dictate lysosomal sorting by exclusion from endosome sorting tubules. Sorting to the lysosome by the C14 motif is cholesterol dependent. Perturbations of the C14 motif by unsaturation enable GM1 entry into endosomal sorting tubules of the recycling and retrograde pathways independent of cholesterol. Unsaturation occurring beyond the C14 motif in very long acyl chains rescues lysosomal sorting. These results define a structural motif underlying the membrane organization of sphingolipids and implicate cholesterol-sphingolipid nanodomain formation in sorting mechanisms.
复杂的神经酰胺脂质表现出多种神经酰胺酰链结构，这些结构影响它们的运输和细胞内分布，但目前尚不清楚细胞如何区分不同的神经酰胺以影响这种分类。为了解决这个问题，我们合成了一系列具有天然变化酰链的 GM1 糖脂，并定量评估了它们在不同内吞途径中的分类。我们发现，至少 14 个饱和碳原子从水双层界面的 C1 延伸，通过排除内体分选小管来决定溶酶体的分类。由 C14 基序介导的分类依赖于胆固醇。通过不饱和作用破坏 C14 基序，使得 GM1 能够进入胆固醇非依赖性的再循环和逆行途径的内体分选小管。在非常长的酰链中超过 C14 基序的不饱和作用恢复溶酶体的分类。这些结果定义了神经酰胺脂质膜组织的结构基序，并暗示胆固醇神经酰胺纳米域形成与分类机制有关。
