RRC ID 67993
Author Hattori N, Nukada T, Oda M, Tanaka S, Ogawa T, Shiota K.
Title Evaluation of the role of N-linked oligosaccharides in rat placental lactogen action by site-directed mutagenesis.
Journal Endocr J
Abstract To evaluate the role of N-linked oligosaccharides in the molecular action of rat placental lactogen (PL), recombinant PL-Im (recPL-Im) and three recPL-Im mutants were produced in COS-7 cells. The mutants, carrying Gln substitutions of Asn at putative N-glycosylation sites, were generated via site-directed mutagenesis, i.e. two single mutants (N79Q, N128Q) and one double mutant (N79Q/N128Q). Western blot analysis revealed that wild type recPL-Im had a molecular mass of 34 kDa , which was reduced to 29 kDa by tunicamycin present during expression. N79Q and N128Q had a lower molecular mass than the wild type, and a further decrease was observed for N79Q/N128Q. PL-Im was therefore N-glycosylated at both Asn79 and Asn128. Treatment of the wild type with neuraminidase caused a reduction in molecular mass, indicating that the N-linked oligosaccharides contained N-acetylneuraminic acids. In the Nb2 cell bioassay for lactogenic hormones, recPL-Im and its mutants all had growth-promoting activity but there was a decline in the growth-stimulating potency following decreases in N-glycosylation, i.e. the order of relative potencies was the wild type>N128Q> N79Q>N79Q/N128Q, suggesting that the N-linked oligosaccharides are important in the mitogenic action of the PL-Im. Wild type and all mutants had rat PRL receptor (PRL-R)-binding activity in radioreceptor assays and stimulated JAK2 phosphorylation in Nb2 cells. Interestingly however, the binding activity to PRL-R and phosphorylation of JAK2 was similar in the wild type and mutants, and these results are not in accord with the biological activity. In conclusion, the study suggested that PL-Im has two N-linked oligosaccharides which are involved in its biological activity. The ability of PL-Im to bind PRL-R and activate JAK2 appears to be independent of the N-glycosylation.
Volume 45(5)
Pages 659-74
Published 1998-10-1
DOI 10.1507/endocrj.45.659
PMID 10395247
MeSH Animals COS Cells Computer Simulation Enzyme-Linked Immunosorbent Assay Gene Expression Glycosylation Mutagenesis, Site-Directed Mutation Neuraminidase Oligosaccharides / chemistry Oligosaccharides / metabolism* Placental Lactogen / genetics Placental Lactogen / metabolism* Rats Recombinant Proteins / chemistry Tumor Cells, Cultured Tunicamycin
IF 1.952
Human and Animal Cells COS-7(RCB0539)