α1,6-岩藻糖基转移酶(Fut8)是负责催化核心岩藻糖基化的酶。外源性L-岩藻糖通过GDP-岩藻糖救助途径上调岩藻糖基化水平。本研究利用野生型(Fut8+/+)研究了核心岩藻糖基化与血清中IgG含量之间的关系,Fut8杂合子敲除(Fut8+/-),和Fut8敲除(Fut8-/-)小鼠。与Fut8+/+小鼠相比,Fut8+/-和Fut8-/-小鼠的血清IgG水平较低。外源性L-岩藻糖增加Fut8+/-小鼠的IgG水平,而核心岩藻糖基化IgG与总IgG的比率在Fut8+/+之间没有显着差异,Fut8+/-,和用L-岩藻糖处理的Fut8+/-小鼠。这些比率通过蛋白质印迹测定,凝集素印迹,和质谱分析。实时荧光定量PCR结果表明,IgGFc和新生儿Fc受体的mRNA水平,负责保护IgG的周转,在Fut8+/+中相似,Fut8+/-,和用L-岩藻糖处理的Fut8+/-小鼠。相比之下,Fcγ受体Ⅳ(FcγRⅣ)的表达水平,主要在巨噬细胞和中性粒细胞上表达,与Fut8+/+小鼠相比,在Fut8+/-小鼠中增加。通过施用L-岩藻糖逆转了效果,表明核心岩藻糖基化主要通过Fc-FcγRⅣ降解途径调节IgG水平。始终如一,FcγRⅣ敲除细胞中IgG内化和转胞吞作用被抑制,而Fut8敲除细胞中IgG内化和转胞吞作用被增强。此外,我们评估了抗卵清蛋白的特异性抗体的表达水平,发现它们在Fut8+/-小鼠中下调,用L-岩藻糖给药观察到潜在的恢复。这些发现证实,核心岩藻糖基化在调节血清IgG水平中起着至关重要的作用,这可能提供了对适应性免疫调节新机制的见解。
α1,6-Fucosyltransferase (Fut8) is the enzyme responsible for catalyzing core fucosylation. Exogenous L-fucose upregulates fucosylation levels through the GDP-fucose salvage pathway. This study investigated the relationship between core fucosylation and immunoglobulin G (IgG) amounts in serum utilizing WT (Fut8+/+),
Fut8 heterozygous knockout (
Fut8+/-), and
Fut8 knockout (
Fut8-/-) mice. The IgG levels in serum were lower in
Fut8+/- and
Fut8-/- mice compared with
Fut8+/+ mice. Exogenous L-fucose increased IgG levels in Fut8+/- mice, while the ratios of core fucosylated IgG versus total IgG showed no significant difference among
Fut8+/+,
Fut8+/-, and
Fut8+/- mice treated with L-fucose. These ratios were determined by Western blot, lectin blot, and mass spectrometry analysis. Real-time PCR results demonstrated that mRNA levels of IgG Fc and neonatal Fc receptor, responsible for protecting IgG turnover, were similar among Fut8+/+,
Fut8+/-, and
Fut8+/- mice treated with L-fucose. In contrast, the expression levels of Fc-gamma receptor Ⅳ (FcγRⅣ), mainly expressed on macrophages and neutrophils, were increased in Fut8+/- mice compared to
Fut8+/+ mice. The effect was reversed by administrating L-fucose, suggesting that core fucosylation primarily regulates the IgG levels through the Fc-FcγRⅣ degradation pathway. Consistently, IgG internalization and transcytosis were suppressed in FcγRⅣ-knockout cells while enhanced in Fut8-knockout cells. Furthermore, we assessed the expression levels of specific antibodies against ovalbumin and found they were downregulated in Fut8+/- mice, with potential recovery observed with L-fucose administration. These findings confirm that core fucosylation plays a vital role in regulating IgG levels in serum, which may provide insights into a novel mechanism in adaptive immune regulation.