Link to bioRxiv paper:
http://biorxiv.org/cgi/content/short/2023.04.19.537613v1?rss=1

Authors: Gupta, A., Ruturaj,, Mishra, M., Saha, S., Maji, S., Rodriguez-Boulan, E., Schreiner, R.

Abstract:
We suggest a model of apico-basolateral sorting in polarized epithelia using homologous Cu-ATPases as membrane cargoes. In polarized epithelia, upon copper treatment, homologous copper-ATPases ATP7A and ATP7B traffic from trans-Golgi network (TGN) to basolateral and apical membranes respectively. We characterized sorting pathways of Cu-ATPases between TGN and plasma-membrane and identified the machinery involved. ATP7A and ATP7B reside on distinct domains of TGN and in high copper, ATP7A traffics directly to basolateral membrane, whereas ATP7B traverses common-recycling, apical-sorting and apical-recycling endosomes en-route to apical membrane. Mass-spectrometry identified regulatory partners of ATP7A and ATP7B that include Adaptor Protein-1 complex. Upon knocking-out pan-AP-1, sorting of both copper-ATPases are disrupted. ATP7A loses polarity and localizes on both apical and basolateral surfaces in high copper. Contrastingly, ATP7B loses TGN-retention but retains apical polarity that becomes copper-independent. Using isoform-specific knockouts, we found that AP-1A provides directionality and TGN-retention for both Cu-ATPases, whereas, AP-1B governs polarized trafficking of ATP7B solely. Trafficking phenotypes of Wilson disease-causing ATP7B mutants that disrupts putative ATP7B-AP1 interaction further substantiates the role of AP-1 in apical sorting of ATP7B.

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