During autophagy, autophagosomes are formed to engulf cytoplasmic contents. p62/SQSTM-1 is an autophagic adaptor protein that forms p62 bodies. A unique feature of p62 bodies is that they seem to directly associate with membranous structures. We first investigated the co-localization of mKate2-p62 bodies with phospholipids using click chemistry with propargyl-choline. Propargyl-choline-labeled phospholipids were detected inside the mKate2-p62 bodies, suggesting that phospholipids were present inside the bodies. To clarify whether or not p62 bodies come in contact with membranous structures directly, we investigated the ultrastructures of p62 bodies using in-resin correlative light and electron microscopy of the Epon-embedded cells expressing mKate2-p62. Fluorescent-positive p62 bodies were detected as uniformly lightly osmificated structures by electron microscopy. Membranous structures were detected on and inside the p62 bodies. In addition, multimembranous structures with rough endoplasmic reticulum–like structures that resembled autophagosomes directly came in contact with amorphous-shaped p62 bodies. These results suggested that p62 bodies are unique structures that can come in contact with membranous structures directly:

在自噬过程中，形成自噬体以吞噬细胞质内容物。p62/SQSTM-1 是一种形成 p62 小体的自噬衔接蛋白。p62 小体的一个独特特征是它们似乎与膜结构直接相关。我们首先使用与炔丙基-胆碱的点击化学研究了 mKate2-p62 体与磷脂的共定位。在 mKate2-p62 体内检测到炔丙基胆碱标记的磷脂，表明体内存在磷脂。为了阐明 p62 体是否直接与膜结构接触，我们使用表达 mKate2-p62 的 Epon 包埋细胞的树脂内相关光学和电子显微镜研究了 p62 体的超微结构。荧光阳性 p62 小体通过电子显微镜检测为均匀轻微渗透的结构。在 p62 体上和内部检测到膜结构。此外，具有类似于自噬体的粗糙内质网样结构的多膜结构直接与无定形p62小体接触。这些结果表明 p62 体是可以直接与膜结构接触的独特结构：