Rab11a-positive compartments in proximal tubule cells sort fluid-phase and membrane cargo
The proximal tubule (PT) reabsorbs the majority of sodium, bicarbonate, and chloride ions, phosphate, glucose, water, and plasma proteins from the glomerular filtrate. Despite the critical importance of endocytosis for PT cell (PTC) function, the organization of the endocytic pathway in these cells remains poorly understood.
Multiple Biosynthetic Trafficking Routs for Apically Secreted Proteins in MDCK Cells
Many newly synthesized membrane proteins traverse endocytic intermediates en route to the surface in polarized epithelial cells; however, the biosynthetic itinerary of secreted proteins has not been elucidated. We monitored the trafficking route of two secreted proteins with different apical sorting signals: the N-glycan-dependent cargo glycosylated growth hormone (gGH) and Ensol, a soluble version of endolyn whose apical sorting is independent of N-glycans.
MUC1 traverses apical recycling endosomes along the biosynthetic pathway in polarized MDCK cells
MUC1 is a heavily glycosylated transmembrane protein localized at the apical surface of polarized epithelial cells. Here, we examined the biosynthetic route of newly synthesized MUC1 in polarized Madin-Darby canine kidney (MDCK) cells. Apically and basolaterally destined cargo are sorted at the trans-Golgi network into distinct vesicles, and proteins with lipid raft-dependent apical targeting signals and glycan-dependent apical targeting signals appear to specifically transit apical early endosomes (AEEs) and apical recycling endosomes (AREs), respectively.