Neurons are highly polarized cells having distinct somatodendritic and axonal domains. Here we report that polarized sorting of the Cu(2+) transporter ATP7B and the vesicle-SNARE VAMP4 to the somatodendritic domain of rat hippocampal neurons is mediated by recognition of dileucine-based signals in the cytosolic domains of the proteins by the σ1 subunit of the clathrin adaptor AP-1. Under basal Cu(2+) conditions, ATP7B was localized to the trans-Golgi network (TGN) and the plasma membrane of the soma and dendrites but not the axon. Mutation of a dileucine-based signal in ATP7B or overexpression of a dominant-negative σ1 mutant resulted in nonpolarized distribution of ATP7B between the somatodendritic and axonal domains. Furthermore, addition of high Cu(2+) concentrations, previously shown to reduce ATP7B incorporation into AP-1-containing clathrin-coated vesicles, caused loss of TGN localization and somatodendritic polarity of ATP7B. These findings support the notion of AP-1 as an effector of polarized sorting in neurons and suggest that altered polarity of ATP7B in polarized cell types might contribute to abnormal copper metabolism in the MEDNIK syndrome, a neurocutaneous disorder caused by mutations in the σ1A subunit isoform of AP-1.
© 2015 Jain et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).