Targeting of Protein ERGIC-53 to the ER/ERGIC/cis-Golgi Recycling Pathway

• Published in: The Journal of cell biology 1995-10, Vol.131 (1), p.57-67
• Main Authors: Itin, Christian, Schindler, Richard, Hauri, Hans-Peter
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Animals; Cell Line - metabolism; Cells; Cellular biology; COS cells; Endoplasmic Reticulum, Rough - metabolism; Enzymes; Epitopes; Epitopes - metabolism; Glycosylation; Golgi Apparatus - metabolism; HeLa cells; Humans; Lectins; Mannose-Binding Lectins; Membrane proteins; Membrane Proteins - metabolism; Membrane Proteins - ultrastructure; Membranes; Molecular Sequence Data; Phenylalanine - physiology; Proteins; Recombinant Proteins - metabolism; Recycling; T lymphocytes
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.131.1.57

ERGIC-53 is a lectin-type membrane protein that continuously recycles between the ER, ER-Golgi intermediate compartment (ERGIC) and the cis-Golgi. To identify the targeting signals that mediate this recycling, N-glycosylated and myc-tagged variants of ERGIC-53 were constructed. By monitoring endoglycosidase H resistance, we measured the loss from the ER-ERGIC-cis-Golgi cycle of ERGIC-53. A domain exchange approach with the plasma membrane reporter protein CD4 showed that the transmembrane and the lumenal domains are not sufficient, while the cytoplasmic domain of ERGIC-53 is required and sufficient for pre-medial-Golgi localization. However, the ERGIC-53 cytoplasmic domain on CD4 lead to increased ER-staining by immunofluorescence microscopy indicating that this domain alone cannot provide for unbiased recycling through the ER-ERGIC-cis-Golgi compartments. Complete progress through the ER-ERGIC-cis-Golgi recycling pathway requires the cytoplasmic domain acting together with the lumenal domain of ERGIC-53. Dissection of the cytoplasmic domain revealed a COOH-terminal di-lysine ER-retrieval signal, KKFF, and an RSQQE targeting determinant adjacent to the transmembrane domain. Surprisingly, the two COOH-terminal phenylalanines influence the targeting. They reduce the ER-retrieval capacity of the di-lysine signal and modulate the RSQQE determinant.