Endosome recycling integrity

Fig. 6.2. Model for how FcRn rescues IgG from catabolism by recycling and transcytosis. IgG and many other soluble proteins are present in extracellular fluids. Vascular endothelial cells are active in fluid phase endocytosis of blood proteins. Material taken up by these cells enters the endosomes where FcRn is found as an integral membrane protein. The IgG then binds FcRn in this acidic environment. This binding results in transport of the IgG to the apical plasma membrane for recycling into the circulation, or to the basolateral membrane for transcytosis into the extracellular space. Exposure to a neutral pFI in both locations then results in the release of IgG. The remaining soluble proteins are channeled to the lysosomal degradation pathway.

Shin, H., Morinaga, N., Masatoshi, N., and Nakayama, K. (2004). BIG2, a guanine nucleotide exchange factor for ADP-ribosylation factors Its localization to recycling endosomes and implication in the endosome integrity. Mol. Biol. Cell 15, 5283-5294. 

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