Human dolichol-phosphate-mannose synthase consists of three subunits, DPM1, DPM2 and DPM3

Abstract

Dolichol-phosphate-mannose (DPM) synthase generates mannosyl donors for glycosylphosphatidylinositols, N-glycan and protein O-and C-mannosylation. In Saccharomyces cerevisiae, this enzyme is encoded by DPM1. We reported previously that mammalian DPM synthase contains catalytic DPM1 and regulatory DPM2 subunits, and that DPM1 requires DPM2 for its stable expression in the endoplasmic reticulum. Here we report that human DPM synthase consists of three subunits. The third subunit, DPM3, comprises 92 amino acids associated with DPM1 via its C-terminal domain and with DPM2 via its N-terminal portion. The stability of DPM3 was dependent upon DPM2. However, overexpression of DPM3 in Lec15 cells, a null mutant of DPM2, restored the biosynthesis of DPM with an increase in DPM1, indicating that DPM3 directly stabilized DPM1. Therefore, DPM2 stabilizes DPM3 and DPM3 stabilizes DPM1. DPM synthase activity was 10 times higher in the presence of DPM2, indicating that DPM2 also plays a role in the enzymatic reaction. Schizosaccharomyces pombe has proteins that resemble three human subunits; S.pombe DPM3 restored biosynthesis of DPM in Lec15 cells, indicating its orthologous relationship to human DPM3.

N-Linked Protein Glycosylation in the Endoplasmic Reticulum

“…Dol-P-Man is generated by the Dol-P-Man synthase. Although in yeast DPM1 encodes Dol-P-Man synthase (Orlean et al 1988), the mammalian enzyme is a complex of three proteins, in which the homolog of Dpm1p is the catalytic subunit (Maeda et al 1998;Maeda et al 2000). Dol-P-Man is not only required for LLO biosynthesis but is also needed for O-mannosylation, glycosyl phosphatidylinositol (GPI) anchor biosynthesis, and C-mannosylation, a rare protein modification of tryptophan side chains (Orlean 1990;Doucey et al 1998).…”

In Vitro Phosphorylation by cAMP-dependent Protein Kinase Up-regulates Recombinant Saccharomyces cerevisiae Mannosylphosphodolichol Synthase

“…On the other hand, human and mouse homologs of DPM1, hDPM1, and mDPM1 did not complement the DPMS mutant in Lec15 cells. This led to establish that mammalian DPMS is a multicomponent enzyme represented by the catalytic subunit DPM1 and two accessory proteins DPM2 and DPM3 (33)(34)(35). Most striking, however, is that Dol-P-Man synthase from every known source has a serine residue in the position corresponding to serine 141 in S. cerevisiae DPMS.…”

The O-Mannosylation Pathway: Glycosyltransferases and Proteins Implicated in Congenital Muscular Dystrophy

“…Dolichol-phosphate Mannose Synthase-Dolichol-phosphate mannose (DPM) is the donor for luminal ER mannosylation, including N-, O-, and C-glycosylation as well as glycophosphatidylinositol anchor biosynthesis (34). DPM is synthesized from GDP-Man and dolichol phosphate via an inverting mechanism on the cytosolic side of the ER (34).…”

“…DPM is synthesized from GDP-Man and dolichol phosphate via an inverting mechanism on the cytosolic side of the ER (34). This reaction is catalyzed by the DPM synthase complex (34).…”

“…DPM is synthesized from GDP-Man and dolichol phosphate via an inverting mechanism on the cytosolic side of the ER (34). This reaction is catalyzed by the DPM synthase complex (34). The catalytic activity is performed by DPM1, a dolichol-phosphate ␤-D-mannosyltransferase belonging to the glycosyltransferase 2 (GT2) family of the CAZy (Carbohydrate-Active enZYmes) Database (34).…”