Human EDEM2, a novel homolog of family 47 glycosidases, is involved in ER-associated degradation of glycoproteins |
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Authors: | Mast Steven W Diekman Krista Karaveg Khanita Davis Ann Sifers Richard N Moremen Kelley W |
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Institution: | Department of Biochemistry and Molecular Biology and Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602-4712, USA. |
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Abstract: | In the endoplasmic reticulum (ER), misfolded proteins are retrotranslocated to the cytosol and degraded by the proteasome in a process known as ER-associated degradation (ERAD). Early in this pathway, a proposed lumenal ER lectin, EDEM, recognizes misfolded glycoproteins in the ER, disengages the nascent molecules from the folding pathway, and facilitates their targeting for disposal. In humans there are a total of three EDEM homologs. The amino acid sequences of these proteins are different from other lectins but are closely related to the Class I mannosidases (family 47 glycosidases). In this study, we characterize one of the EDEM homologs from Homo sapiens, which we have termed EDEM2 (C20orf31). Using recombinantly generated EDEM2, no alpha-1,2 mannosidase activity was observed. In HEK293 cells, recombinant EDEM2 is localized to the ER where it can associate with misfolded alpha1-antitrypsin. Overexpression of EDEM2 accelerates the degradation of misfolded alpha1-antitrypsin, indicating that the protein is involved in ERAD. |
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Keywords: | EDEM / EDEM2 / ERAD / ER quality control / mannosidase |
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