The two subunits of the asialoglycoprotein receptor contain different sorting information

Fuhrer, C. and Geffen, I. and Huggel, K. and Spiess, M.. (1994) The two subunits of the asialoglycoprotein receptor contain different sorting information. Journal of biological chemistry, Vol. 269, H. 5. pp. 3277-3282.

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Official URL: http://edoc.unibas.ch/dok/A5258079

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The human asialoglycoprotein receptor, an endocytic transport receptor of the basolateral surface of hepatocytes, is a hetero-oligomer of two homologous subunits H1 and H2. The cytoplasmic domain of H1 has been shown previously to contain a tyrosine-based signal for endocytosis and basolateral sorting. Here, we have investigated sorting determinants within subunit H2 and their contribution to the targeting of the hetero-oligomeric receptor complex. Despite extensive sequence homology, H2 expressed separately in fibroblast cells was endocytosed poorly, and mutation of phenylalanine 5 (corresponding to the critical tyrosine in H1) did not further reduce internalization. Consistent with this observation, ligand uptake by receptors composed of H1 lacking tyrosine 5 and H2 was inefficient. With respect to polarized transport in Madin-Darby canine kidney cells, H2 could not be analyzed separately, because in the absence of H1 subunit H2 was completely degraded intracellularly. Coexpression of both subunits yielded ligand-binding receptors located specifically on the basolateral surface. The mutant H1(5A) (tyrosine 5 replaced by alanine) is approximately 55% apical in the absence of H2. In cells expressing H1(5A) together with H2, however, subunit H2 directed receptor complexes exclusively to the basolateral domain. Phenylalanine 5 is not essential for basolateral transport. Thus, whereas the endocytosis signal of the hetero-oligomeric asialoglycoprotein receptor resides exclusively in subunit H1, polarized transport to the basolateral domain of Madin-Darby canine kidney cells may involve two signals, only one of which is active for endocytosis.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Growth & Development > Biochemistry (Spiess)
UniBasel Contributors:Spiess, Martin
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Society of Biological Chemists
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:23
Deposited On:22 Mar 2012 13:34

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