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，形成了自噬小体以吞噬细胞质内容物。p62 / SQSTM-1是形成p62体的自噬衔接蛋白。p62体的独特之处在于它们似乎直接与膜结构相关。我们首先使用点击化学与炔丙基胆碱研究了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，表明该体内存在磷脂。为了阐明p62体是否直接与膜结构接触，我们使用树脂内相关光和电子显微镜对表达mKate2-p62的Epon包埋的细胞研究了p62体的超微结构。通过电子显微镜将荧光阳性的p62体检测为均匀轻度膨化的结构。在p62体内和内部均检测到膜状结构。此外，具有类似于自噬小体的内质网状粗糙结构的多膜结构直接与无定形p62体接触。这些结果表明，p62体是可以与膜结构直接接触的独特结构：