Effects of Differential Glycosylation of Glycodelins on Lymphocyte Survival

Cheuk-Lun Lee,Poh-Choo Pang,William S.B Yeung,Bérangère Tissot,Maria Panico,Terence T.H Lao,Ivan K Chu,Kai-Fai Lee,Man-Kin Chung,Kevin K.W Lam,Riitta Koistinen,Hannu Koistinen,Markku Seppälä,Howard R Morris,Anne Dell,Philip C.N Chiu

doi:10.1074/jbc.m807960200

Abstract

Glycodelin is a human glycoprotein with four reported glycoforms, namely glycodelin-A (GdA), glycodelin-F (GdF), glycodelin-C (GdC), and glycodelin-S (GdS). These glycoforms have the same protein core and appear to differ in their N-glycosylation. The glycosylation of GdA is completely different from that of GdS. GdA inhibits proliferation and induces cell death of T cells. However, the glycosylation and immunomodulating activities of GdF and GdC are not known. This study aimed to use ultra-high sensitivity mass spectrometry to compare the glycomes of GdA, GdC, and GdF and to study the relationship between the immunological activity and glycosylation pattern among glycodelin glycoforms. Using MALDI-TOF strategies, the glycoforms were shown to contain an enormous diversity of bi-, tri-, and tetra-antennary complex-type glycans carrying Galbeta1-4GlcNAc (lacNAc) and/or GalNAcbeta1-4GlcNAc (lacdiNAc) antennae backbones with varying levels of fucose and sialic acid substitution. Interestingly, they all carried a family of Sda (NeuAcalpha2-3(GalNAcbeta1-4)Gal)-containing glycans, which were not identified in the earlier study because of less sensitive methodologies used. Among the three glycodelins, GdA is the most heavily sialylated. Virtually all the sialic acid on GdC is located on the Sda antennae. With the exception of the Sda epitope, the GdC N-glycome appears to be the asialylated counterpart of the GdA/GdF glycomes. Sialidase activity, which may be responsible for transforming GdA/GdF to GdC, was detected in cumulus cells. Both GdA and GdF inhibited the proliferation, induced cell death, and suppressed interleukin-2 secretion of Jurkat cells and peripheral blood mononuclear cells. In contrast, no immunosuppressive effect was observed for GdS and GdC.

Highlights

Glycodelin is a member of the lipocalin family
The present study aims to identify the effect of all four glycodelin isoforms on lymphocyte viability, cell death, and interleukin-2 (IL-2) secretion and to correlate these bioactivities with their glycosylation patterns determined by mass spectrometry
Consistent with our previous data [5], GdF was characterized by significantly lower affinity to Ulex europaeus agglutinin (p Ͻ 0.05) and higher affinity to succinylated wheat germ agglutinin (p Ͻ 0.05), whereas GdS was characterized by a low affinity to Wisteria floribunda agglutinin (p Ͻ 0.05) when compared with other isoforms

Summary

Introduction

Glycodelin is a member of the lipocalin family. It consists of 180 amino acid residues [1] with two sites of N-linked glycosylation. Among the four glycodelin isoforms, only the N-glycan structures of GdA and GdS have been previously determined. The glycan structures of GdF and GdC are not known, they differ in lectin-binding properties and isoelectric point from the other two glycodelin isoforms [5]. Glycosylation determines the biological activities of the glycodelin isoforms [2, 10] Both GdA and GdF inhibit the spermatozoa-zona pellucida binding [11] via fucosyltransferase-5 [12], but only the latter inhibits progesterone-induced acrosome reaction, preventing a premature acrosome reaction of the spermatozoa. Except for the effects on fertilization, GdA is involved in fetomaternal defense This glycodelin isoform suppresses proliferation and induces apoptosis of T cells [2] and inhibits natural killer cell [14] and B-cell [15] activities. The present study aims to identify the effect of all four glycodelin isoforms on lymphocyte viability, cell death, and interleukin-2 (IL-2) secretion and to correlate these bioactivities with their glycosylation patterns determined by mass spectrometry

Objectives

Results

Conclusion