N-glycosylation is required for secretion-competent human plasma phospholipid transfer protein

Shi Jing Qu, Hui Zhen Fan, Baiba K. Gillard, Henry J. Pownall

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

Human plasma phospholipid transfer protein (PLTP) contains six potential N-glycosylation sites (Asn-X-Ser). To study the role of these sites on PLTP structure and function, seven variants in which asparagine (N) residues were converted to glycine (G) were prepared by site-directed mutagenesis. These were N47G, N77G, N100G, N126G, N 228G, N381G and N47, 77, 100, 126, 228, 381G (NnullG). These variants and wild-type (WT) PLTP were expressed in COS-7 cells. Intracellular and secreted PLTP mass was analyzed by Western blots and quantitative enzyme-linked immunosorbent assay; PLTP activities in cellular lysates and media were based on the transfer of [3H] dipalmitoylphosphatidylcholine from phospholipid single bilayer vesicles to HDL. NnullG was not detected intracellularly. N381G was similar to WT PLTP with respect to specific activity and secretion efficiency. The specific activities of N47G, N77G, N100G, N126G, N228G and N381G were similar in cell lysate (range = 67-90% WT) and medium (range = 65-77% WT). Intracellular masses of these PLTP variants were similar to that of WT (Mean = 103% WT); mean secreted mass was 88% WT. These results suggest that secretion-competent PLTP requires glycosylation but that no single glycosylation site is required.

Original languageEnglish (US)
Pages (from-to)167-173
Number of pages7
JournalProtein Journal
Volume25
Issue number2
DOIs
StatePublished - Feb 2006

Keywords

  • COS cells
  • Glycosylation
  • Lipid transfer
  • Mutagenesis
  • Protein secretion

ASJC Scopus subject areas

  • Biochemistry

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