Dataset Information

Role of malectin in Glc(2)Man(9)GlcNAc(2)-dependent quality control of ?1-antitrypsin.

ABSTRACT: Malectin was first discovered as a novel endoplasmic reticulum (ER)-resident lectin from Xenopus laevis that exhibits structural similarity to bacterial glycosylhydrolases. Like other intracellular lectins involved in glycoprotein quality control, malectin is highly conserved in animals. Here results from in vitro membrane-based binding assays and frontal affinity chromatography confirm that human malectin binds specifically to Glc(2)Man(9)GlcNAc(2) (G2M9) N-glycan, with a K(a) of 1.97 × 10(5) M(-1), whereas binding to Glc(1)Man(9)GlcNAc(2) (G1M9), Glc(3)Man(9)GlcNAc(2) (G3M9), and other N-glycans is barely detectable. Metabolic labeling and immunoprecipitation experiments demonstrate that before entering the calnexin cycle, the folding-defective human ?1-antitrypsin variant null Hong Kong (AT(NHK)) stably associates with malectin, whereas wild-type ?1-antitrypsin (AT) or N-glycan-truncated variant of AT(NHK) (AT(NHK)-Q3) dose not. Moreover, malectin overexpression dramatically inhibits the secretion of AT(NHK) through a mechanism that involves enhanced ER-associated protein degradation; by comparison, the secretion of AT and AT(NHK)-Q3 is only slightly affected by malectin overexpression. ER-stress induced by tunicamycin results in significantly elevated mRNA transcription of malectin. These observations suggest a possible role of malectin in regulating newly synthesized glycoproteins via G2M9 recognition.

SUBMITTER: Chen Y

PROVIDER: S-EPMC3183012 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature

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Role of malectin in Glc(2)Man(9)GlcNAc(2)-dependent quality control of α1-antitrypsin.

Chen Yang Y Hu Dan D Yabe Rikio R Tateno Hiroaki H Qin Sheng-Ying SY Matsumoto Naoki N Hirabayashi Jun J Yamamoto Kazuo K

Molecular biology of the cell 20110803 19

Malectin was first discovered as a novel endoplasmic reticulum (ER)-resident lectin from Xenopus laevis that exhibits structural similarity to bacterial glycosylhydrolases. Like other intracellular lectins involved in glycoprotein quality control, malectin is highly conserved in animals. Here results from in vitro membrane-based binding assays and frontal affinity chromatography confirm that human malectin binds specifically to Glc(2)Man(9)GlcNAc(2) (G2M9) N-glycan, with a K(a) of 1.97 × 10(5) M ...[more]

PMID: 21813736

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Project description:BACKGROUND: Protein-based therapeutics represent the fastest growing class of compounds in the pharmaceutical industry. This has created an increasing demand for powerful expression systems. Yeast systems are widely used, convenient and cost-effective. Yarrowia lipolytica is a suitable host that is generally regarded as safe (GRAS). Yeasts, however, modify their glycoproteins with heterogeneous glycans containing mainly mannoses, which complicates downstream processing and often interferes with protein function in man. Our aim was to glyco-engineer Y. lipolytica to abolish the heterogeneous, yeast-specific glycosylation and to obtain homogeneous human high-mannose type glycosylation. RESULTS: We engineered Y. lipolytica to produce homogeneous human-type terminal-mannose glycosylated proteins, i.e. glycosylated with Man?GlcNAc? or Man?GlcNAc?. First, we inactivated the yeast-specific Golgi ?-1,6-mannosyltransferases YlOch1p and YlMnn9p; the former inactivation yielded a strain producing homogeneous Man?GlcNAc? glycoproteins. We tested this strain by expressing glucocerebrosidase and found that the hypermannosylation-related heterogeneity was eliminated. Furthermore, detailed analysis of N-glycans showed that YlOch1p and YlMnn9p, despite some initial uncertainty about their function, are most likely the ?-1,6-mannosyltransferases responsible for the addition of the first and second mannose residue, respectively, to the glycan backbone. Second, introduction of an ER-retained ?-1,2-mannosidase yielded a strain producing proteins homogeneously glycosylated with Man?GlcNAc?. The use of the endogenous LIP2pre signal sequence and codon optimization greatly improved the efficiency of this enzyme. CONCLUSIONS: We generated a Y. lipolytica expression platform for the production of heterologous glycoproteins that are homogenously glycosylated with either Man?GlcNAc? or Man?GlcNAc? N-glycans. This platform expands the utility of Y. lipolytica as a heterologous expression host and makes it possible to produce glycoproteins with homogeneously glycosylated N-glycans of the human high-mannose-type, which greatly broadens the application scope of these glycoproteins.

Dataset Information

Role of malectin in Glc(2)Man(9)GlcNAc(2)-dependent quality control of ?1-antitrypsin.

Publications

Role of malectin in Glc(2)Man(9)GlcNAc(2)-dependent quality control of α1-antitrypsin.

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