The Recycling Endosome of Madin-Darby Canine Kidney Cells Is a Mildly Acidic Compartment Rich in Raft Components

作者：Raluca Gagescu, Nicolas Demaurex, Robert G. Parton, Walter Hunziker, Lukas Alfons Huber, Jean Grüenberg · 发表于：Molecular Biology of the Cell · 年份：2000 · DOI：10.1091/mbc.11.8.2775 · 被引用次数：318 · 研究领域：Caveolin-1 and cellular processes、Ion Transport and Channel Regulation、Cellular transport and secretion

We present a biochemical and morphological characterization of recycling endosomes containing the transferrin receptor in the epithelial Madin-Darby canine kidney cell line. We find that recycling endosomes are enriched in molecules known to regulate transferrin recycling but lack proteins involved in early endosome membrane dynamics, indicating that recycling endosomes are distinct from conventional early endosomes. We also find that recycling endosomes are less acidic than early endosomes because they lack a functional vacuolar ATPase. Furthermore, we show that recycling endosomes can be reached by apically internalized tracers, confirming that the apical endocytic pathway intersects the transferrin pathway. Strikingly, recycling endosomes are enriched in the raft lipids sphingomyelin and cholesterol as well as in the raft-associated proteins caveolin-1 and flotillin-1. These observations may suggest that a lipid-based sorting mechanism operates along the Madin-Darby canine kidney recycling pathway, contributing to the maintenance of cell polarity. Altogether, our data indicate that recycling endosomes and early endosomes differ functionally and biochemically and thus that different molecular mechanisms regulate protein sorting and membrane traffic at each step of the receptor recycling pathway.