Clathrin and AP1B: Key roles in basolateral trafficking through trans-endosomal routes

Abstract 

Research following introduction of the MDCK model system to study epithelial polarity (1978) led to an initial paradigm that posited independent roles of the trans Golgi network (TGN) and recycling endosomes (RE) in the generation of, respectively, biosynthetic and recycling routes of plasma membrane (PM) proteins to apical and basolateral PM domains. This model dominated the field for 20years. However, studies over the past decade and the discovery of the involvement of clathrin and clathrin adaptors in protein trafficking to the basolateral PM has led to a new paradigm. TGN and RE are now believed to cooperate closely in both biosynthetic and recycling trafficking routes. Here, we critically review these recent advances and the questions that remain unanswered.

Keywords: Epithelial polarity, Sorting, Clathrin, Adaptor, Endosome

Abbreviations: ASE and BSE, apical and basolateral sorting endosomes, AGPR, asialoglycoprotein receptor, ClC-2, chloride channel-2, CRE, common recycling endosomes, EGFR, epidermal growth factor, EPP, epithelial polarity program, ER, endoplasmic reticulum, GPI, glycosyl-phosphatidylinositol, GFP, green fluorescent protein, HA, influenza hemagglutinin, HRP, horse radish peroxidase, LDLR, low-density lipoprotein receptor, LRP1, low-density lipoprotein receptor-related protein 1, M6PR, mannose 6-phosphate receptor, PM, plasma membrane, pIgR, polyimmunoglobulin receptor, PKD, protein kinase D, RE, recycling endosomes, Tf, transferrin, TfR, Tf receptor, TGN and TGF-α, trans Golgi network and transforming growth factor α, VSVG, vesicular stomatitis virus G, WGA, wheat germ agglutinin