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Newly synthesized and recycling pools of the apical protein gp135 do not occupy the same compartments
Author(s) -
Stoops Emily H.,
Hull Michael,
Caplan Michael J.
Publication year - 2016
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/tra.12449
Subject(s) - endosome , endocytic cycle , microbiology and biotechnology , apical membrane , biology , golgi apparatus , transport protein , protein targeting , endomembrane system , membrane protein , biochemistry , endocytosis , membrane , endoplasmic reticulum , cell , intracellular
Polarized epithelial cells sort newly synthesized and recycling plasma membrane proteins into distinct trafficking pathways directed to either the apical or basolateral membrane domains. While the trans‐Golgi network is a well‐established site of protein sorting, increasing evidence indicates a key role for endosomes in the initial trafficking of newly synthesized proteins. Both basolateral and apical proteins have been shown to traverse endosomes en route to the plasma membrane. In particular, apical proteins traffic through either subapical early or recycling endosomes. Here we use the SNAP tag system to analyze the trafficking of the apical protein gp135, also known as podocalyxin. We show that newly synthesized gp135 traverses the apical recycling endosome, but not the apical early endosomes (AEEs). In contrast, post‐endocytic gp135 is delivered to the AEE before recycling back to the apical membrane. The pathways pursued by the newly synthesized and recycling gp135 populations do not detectably intersect, demonstrating that the biosynthetic and post‐endocytic pools of this protein are subjected to distinct sorting processes.