DPM2 regulates biosynthesis of dolichol phosphate-mannose in mammalian cells: correct subcellular localization and stabilization of DPM1, and binding of dolichol phosphate.
Biosynthesis of glycosylphosphatidylinositol and N-glycan precursor is dependent upon a mannosyl donor, dolichol phosphate-mannose (DPM). The Thy-1negative class E mutant of mouse lymphoma and Lec15 mutant Chinese hamster ovary (CHO) cells are incapable of DPM synthesis. The class E mutant is defective in the DPM1 gene which encodes a mammalian homologue of Saccharomyces cerevisiae Dpm1p that is a DPM synthase, whereas Lec15 is a different mutant, indicating that mammalian DPM1 is not sufficient for DPM synthesis. Here we report expression cloning of a new gene, DPM2, which is defective in Lec15 cells. DPM2, an 84 amino acid membrane protein expressed in the endoplasmic reticulum (ER), makes a complex with DPM1 that is essential for the ER localization and stable expression of DPM1. Moreover, DPM2 enhances binding of dolichol phosphate, a substrate of DPM synthase. Mammalian DPM1 is catalytic because a fusion protein of DPM1 that was stably expressed in the ER synthesized DPM without DPM2. Therefore, biosynthesis of DPM in mammalian cells is regulated by DPM2.
Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan.
Y
Y
Maeda
S
S
Tomita
R
R
Watanabe
K
K
Ohishi
T
T
Kinoshita
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002451:Cell Compartmentation; D003001:Cloning, Molecular; D004287:Dolichol Monophosphate Mannose / Q000378:metabolism*; D004288:Dolichol Phosphates / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology; D015870:Gene Expression; D005816:Genetic Complementation Test; D006801:Humans; D008364:Mannosyltransferases / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D051381:Rats; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D002352:Carrier Proteins; D004288:Dolichol Phosphates; D008565:Membrane Proteins; D004287:Dolichol Monophosphate Mannose; C115077:DPM2 protein, human; D008364:Mannosyltransferases; C022755:dolichyl-phosphate beta-D-mannosyltransferase