Basolateral cycling mediated by a lumenal domain targeting determinant.

All identified basolateral sorting signals of integral membrane proteins are cytoplasmically disposed, suggesting that basolateral targeting is mediated exclusively by direct interaction with vesicle coat components. Here, we report that GPP130, a cis-Golgi protein that undergoes endosome-to-Golgi retrieval using the late endosome-bypass pathway in nonpolarized cells, cycles via the basolateral membrane in polarized MDCK cells. Significantly, the membrane-proximal lumenal domain of GPP130, which mediates GPP130 localization and trafficking in nonpolarized cells, was both necessary and sufficient for basolateral cycling in MDCK cells. The use of lumenal determinants for both basolateral cycling and endosome-to-Golgi retrieval suggests that a novel receptor-mediated mechanism operates at both the trans-Golgi network and distal sites to sort GPP130 along the late-endosome-bypass retrieval pathway in polarized cells.