Proteoglycans in macrophages: characterization and possible role in the cellular uptake of lipoproteins
Proteoglycans in macrophages: characterization and possible role in the cellular uptake of lipoproteins
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DOI：
10.1042/bj3310743
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发表时间：
1998-05-01
影响因子：
4.1
通讯作者：
Kolset, SO
中科院分区：
文献类型：
--
作者：
Halvorsen, B;Aas, UK;Kolset, SO
用[S-35]硫酸盐孵育鼠巨噬细胞系J774。细胞相关的S-35标记的大分子被证明是蛋白聚糖和糖胺聚糖在类似的数量。通过将[S-35]硫酸盐标记的细胞与胰蛋白酶孵育15分钟，研究了细胞表面蛋白聚糖的可能存在。70%游离糖胺聚糖链和30%蛋白聚糖。后一种组分经HNO 2处理证明含有硫酸乙酰肝素。在未用胰蛋白酶处理的总细胞部分中，显示小但显著的部分是硫酸软骨素蛋白聚糖。细胞相关的糖胺聚糖含有硫酸软骨素和硫酸乙酰肝素。为了研究巨噬细胞中细胞表面蛋白聚糖的可能生物学功能，将细胞与NaClO 3孵育以抑制蛋白聚糖的硫酸化，并与β-D-木糖苷孵育以消除蛋白聚糖的表达。在未经处理的J774细胞中，氧化I-125-酪胺纤维二糖标记的低密度脂蛋白（I-125-TC-LDL）的摄取通常比天然I-125-TC-LDL高2至3倍。在NaClO 3和木糖苷处理后，在37 ℃下天然I-125-TC-LDL的细胞摄取降低25%，而在两种类型的处理后，氧化I-125-TC-LDL的摄取降低35%。清道夫受体A-II和低密度脂蛋白受体的mRNA水平没有受到影响的氯酸钠或木糖苷治疗，此外，液相内吞作用，辣根过氧化物酶的摄取，和受体介导的内吞作用，测量为摄取I-125-TC-卵清蛋白，没有受到氯酸钠治疗的J774细胞。用软骨素酶ABC去除细胞表面硫酸软骨素仅降低了天然I-125-TC-LDL的结合，而用肝素酶去除硫酸乙酰肝素降低了氧化和天然I-125-TC-LDL的结合。脂蛋白脂酶的加入使氧化型I-125-TC-LDL的摄取增加1.7倍，使天然型I-125-TC-LDL的摄取增加2.1倍。前者的结合对NaClO_3处理比后者更敏感。提出的结果支持这样的观点，即泡沫细胞形成巨噬细胞中脂蛋白的一些摄取途径依赖于细胞表面硫酸乙酰肝素和硫酸软骨素的存在。
The murine macrophage cell line J774 was incubated with [S-35]sulphate. The cell-associated S-35-labelled macromolecules were shown to be proteoglycans and glycosaminoglycans in similar amounts. The possible presence of cell-surface proteoglycans was investigated by incubating [S-35]sulphate-labelled cells with trypsin for 15 min. The released material contained approx. 70 % free glycosaminoglycan chains and 30 % proteoglycans. The latter component was demonstrated by HNO2 treatment to contain heparan sulphate. In the total cell fraction not treated with trypsin a small but significant portion was shown to be chondroitin sulphate proteoglycan, The cell-associated glycosaminoglycans contained both chondroitin sulphate and heparan sulphate. To investigate possible biological functions of cell-surface proteoglycans in macrophages, cells were incubated with NaClO3 to inhibit sulphation of proteoglycans and beta-D-xyloside to abrogate proteoglycan expression. The uptake of oxidized I-125-tyraminylcellobiose-labelled low-density lipoprotein (I-125-TC-LDL) was typically two to three times higher than that of native I-125-TC-LDL in untreated J774 cells. The cellular uptake at 37 degrees C of native I-125-TC-LDL was decreased 25% after both NaClO3 and xyloside treatment, whereas the uptake of oxidized I-125-TC-LDL was decreased 35 % after both types of treatment. The mRNA levels for the scavenger receptor A-II and the LDL receptor were not affected by NaClO3 or xyloside treatment, Furthermore, fluid-phase endocytosis, measured as uptake of horseradish peroxidase, and receptor-mediated endocytosis, measured as uptake of I-125-TC-ovalbumin, were not affected by NaClO3 treatment of J774 cells. Removal of cell-surface chondroitin sulphate with chondroitinase ABC decreased only the binding of native I-125-TC-LDL, whereas removal of heparan sulphate with heparitinase decreased the binding of both oxidized and native I-125-TC-LDL. Addition of lipoprotein lipase increased the uptake of oxidized I-125-TC-LDL 1.7 times and the uptake of native I-125-TC-LDL 2.1 times. The binding of the former was more sensitive to NaClO3 treatment than the latter. The results presented support the notion that some of the uptake pathways for lipoproteins in the foam-cell-forming macrophages depend on the presence of cell-surface heparan sulphate and chondroitin sulphate.