The Dictyostelium discoideum beta-1,4-mannosyltransferase gene, mntA, has two periods of developmental expression

Nascent Proteome and Glycoproteome Reveal the Inhibition Role of ALG1 in Hepatocellular Carcinoma Cell Migration

Asparagine-linked glycosylation protein 1 homolog (ALG1) participates in the initial stage of protein N-glycosylation and N-glycosylation has been implicated in the process of hepatocellular carcinoma (HCC) progression. However, whether ALG1 plays a role in human HCC remains unknown. In this study, the expression profile of ALG1 in tumorous and corresponding adjacent non-tumor tissues was analyzed. The relationship of ALG1 expression with clinical features and prognosis of HCC patients was also evaluated using immuno-histochemical method. Here we found ALG1 decreased in HCC tissues compared with adjacent normal liver tissues, which predicted an unfavorable prognosis. Combined with RNA interference, nascent proteome and glycoproteome were determined systematically in Huh7 cell line. Bioinformatics analysis indicated that the differentially expressed proteins participating in the response of ALG1 knockdown were most significantly associated with cell-cell adhesion. Functional studies confirmed that knockdown of ALG1 reduced cell adhesion capacity, and promoted cell migration. Furthermore, down-regulation of H8N2 (on N-glycosite N651) and H5N4S2F1 (on N-glycosite N692) from N-cadherin was identified as a feature of ALG1 knockdown. Our findings revealed that ALG1 controlled the expression of glycosylated N-cadherin and played a role in HCC migration, with implications for prognosis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43657-022-00050-5.

Cloning of the human cDNA which can complement the defect of the yeast mannosyltransferase I-deficient mutant alg 1

The assembly of the lipid-linked oligosaccharide, Glc(3)Man(9)GlcNAc(2)-P-P-Dol, occurs on the rough ER membrane in an ordered stepwise manner. The process is highly conserved among eukaryotes. In order to isolate the human mannosyltransferase I (MT-I) gene involved in the process, we used the Saccharomyces cerevisiae MT-I gene ( ALG1 ), which has already been cloned. On searching the EST database with the amino acid sequence of the ALG1 gene product, we detected seven related human EST clones. A human fetal brain cDNA library was screened by PCR using gene-specific primers based on the EST nucleotide sequences and a 430 bp cDNA fragment was amplified. The cDNA library was rescreened with this 430 bp cDNA, and two cDNA clones (HR1-3 and HR1-4) were isolated and sequenced. On a homology search of the EST database with the nucleotide sequence of HR1-3, we detected a novel human EST clone, AA675921 (GenBank accession number). Based on the nucleotide sequences of AA675921 and HR1-4, we designed gene-specific PCR primers, which allowed to amplify a 1.8 kb cDNA from human fetal brain cDNA. This cDNA was cloned and shown to contain an ORF encoding a protein of 464 amino acids. We designated this ORF as Hmat-1. The amino acid sequence deduced from the Hmat-1 gene showed several highly conserved regions shared with the yeast and nematode MT-I sequences. Furthermore, this 1.8 kb cDNA successfully complemented the S. cerevisiae alg1-1 mutation, indicating that the Hmat-1 gene encodes the human MT-I and that the function of this enzyme was conserved between yeast and human.

Development of recombinant, immobilised beta-1,4-mannosyltransferase for use as an efficient tool in the chemoenzymatic synthesis of N-linked oligosaccharides

The preparation of the conserved core structure of asparagine-linked oligosaccharides found in eukaryotic glycoproteins is an important step towards the synthesis of homogeneous neoglycoproteins. So far, however, the convenient generation of the Manbeta4GlcNAcbeta4GlcNAc (Gn2M) core trisaccharide has proved to be a major obstacle because of the inherent difficulties associated with the synthesis of beta-mannosides. Here we report the overproduction in Escherichia coli of full-length and transmembrane-deleted yeast beta-1, 4-mannosyltransferases as novel N-terminal fusions bearing a decahistidinyl sequence and the minimal human Myc epitope. The recombinant enzymes were highly active and were amenable to immobilisation by nickel(II) chelation and to immunodetection with an anti-Myc monoclonal antibody. The immobilised, transmembrane-deleted enzyme exhibited an apparent Km of 14 microM for the synthetic acceptor substrate analogue, phytanyl-pyrophosphoryl-alpha-N,N'-diacetylchitobioside (PPGn2), under saturating donor conditions. This figure is comparable to those previously reported for native and recombinant yeast beta-1, 4-mannosyltransferases with, respectively, the natural dolichyl-linked acceptor and PPGn2. The validity of the reaction product was confirmed by chromatographic and spectroscopic analysis.