A1 Refereed original research article in a scientific journal
The polarized epithelia-specific mu 1B-adaptin complements mu 1A-deficiency in fibroblasts
Authors: Eskelinen EL, Meyer C, Ohno H, von Figura K, Schu P
Publisher: WILEY
Publication year: 2002
Journal: EMBO Reports
Journal name in source: EMBO REPORTS
Journal acronym: EMBO REP
Volume: 3
Issue: 5
First page : 471
Last page: 477
Number of pages: 7
ISSN: 1469-221X
DOI: https://doi.org/10.1093/embo-reports/kvf092
Abstract
The heterotetrameric AP-1A adaptor complex of clathrin-coated vesicles is ubiquitously expressed. The mu1-adaptin subunit of the complex exists as the ubiquitous mu1A and the polarized epithelia-specific mu1B, which are 80% identical. In polarized epithelia, mu1B is incorporated into the AP-1B complex, which is required for basolateral plasma membrane sorting of the low-density lipoprotein receptor. Binding of AP-1B to subdomains of the trans-Golgi network (TGN) appears to be part of the mechanism by which protein sorting is mediated. We expressed mu1B in mu1A-deficient fibroblasts to test for mu1B function in non-polarized cells. AP-1B complexes were formed and bound to the TGN and to endosomes. Moreover, AP-1B restored the AP-1A-dependent sorting of mannose 6-phosphate receptors between endosomes and the TGN. This demonstrates that mu1A and pi B do have overlapping sorting functions and indicates that AP-1A and AP-1B mediate protein sorting along parallel pathways between the TGN and endosomes in polarized epithelia.
The heterotetrameric AP-1A adaptor complex of clathrin-coated vesicles is ubiquitously expressed. The mu1-adaptin subunit of the complex exists as the ubiquitous mu1A and the polarized epithelia-specific mu1B, which are 80% identical. In polarized epithelia, mu1B is incorporated into the AP-1B complex, which is required for basolateral plasma membrane sorting of the low-density lipoprotein receptor. Binding of AP-1B to subdomains of the trans-Golgi network (TGN) appears to be part of the mechanism by which protein sorting is mediated. We expressed mu1B in mu1A-deficient fibroblasts to test for mu1B function in non-polarized cells. AP-1B complexes were formed and bound to the TGN and to endosomes. Moreover, AP-1B restored the AP-1A-dependent sorting of mannose 6-phosphate receptors between endosomes and the TGN. This demonstrates that mu1A and pi B do have overlapping sorting functions and indicates that AP-1A and AP-1B mediate protein sorting along parallel pathways between the TGN and endosomes in polarized epithelia.
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