Luescher B, Bron C
J Immunol. 1985 Feb;134(2):1084-9.
The biosynthesis and the maturation of Thy-1 antigen of mouse thymocytes have been studied by using a xenogeneic rabbit anti-mouse Thy-1 antibody. The earliest form of Thy-1 detected after a 5-min pulse with [35S]methionine and [35S]cysteine had an apparent m.w. of 26,500. During chase, this band converted to a molecular ratio (Mr) = 25,000 polypeptide, probably derived from the latter by trimming of glucose or mannose residues from the three high-mannose glycan units of Thy-1. Mature Thy-1 molecules were detected at the cell surface after a 15-min chase. At least one of the three N-linked oligosaccharide units was shown to be in the high mannose form at the cell surface, as indicated by its susceptibility to endo-beta-N-acetylglucosaminidase H digestion. Treatment of the early and late forms of Thy-1 antigen with endo-beta-N-acetylglucosaminidase F generated a single polypeptide of Mr = 13,500. The same precursor was obtained when cells were labeled in the presence of tunicamycin. This indicates the absence of O-linked glycan in the mature cell surface antigen. Finally, the resistance of Thy-1 antigen to trypsin digestion when associated with membranes confirmed that this molecule has no cytoplasmically oriented portion.
利用异种兔抗小鼠Thy-1抗体研究了小鼠胸腺细胞Thy-1抗原的生物合成及成熟过程。用[35S]甲硫氨酸和[35S]半胱氨酸脉冲标记5分钟后检测到的最早形式的Thy-1，其表观分子量为26,500。在追踪过程中，这条带转化为分子比（Mr）= 25,000的多肽，可能是通过从Thy-1的三个高甘露糖聚糖单元中去除葡萄糖或甘露糖残基而从后者衍生而来。追踪15分钟后在细胞表面检测到成熟的Thy-1分子。如对内切β-N-乙酰葡糖胺酶H消化敏感所示，三个N-连接寡糖单元中至少有一个在细胞表面呈高甘露糖形式。用内切β-N-乙酰葡糖胺酶F处理Thy-1抗原的早期和晚期形式，产生了一个Mr = 13,500的单一多肽。当细胞在衣霉素存在下进行标记时，也获得了相同的前体。这表明成熟细胞表面抗原中不存在O-连接聚糖。最后，Thy-1抗原与膜结合时对胰蛋白酶消化具有抗性，证实该分子没有面向细胞质的部分。
