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首页> 外文期刊>European Journal of Cell Biology: Journal of Deutsche Gesellschaft fur Elektronenmikroskopie: Journal of Deutsche Gesellschaft fur Zellbiologie >Iodination of mature cathepsin D in thyrocytes as an indicator for itstransport to the cell surface
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Iodination of mature cathepsin D in thyrocytes as an indicator for itstransport to the cell surface

机译：甲状腺细胞中成熟组织蛋白酶D的碘化作用作为其向细胞表面迁移的指标

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摘要

Thyrocytes are known for their ability to iodinate thyroglobulin from which the thyroid hormones are generated. In the intact thyroid gland the iodination process is almost exclusively executed at the apical plasma membrane of thyroid epithelial cells, Here, we show that freshly isolated thyrocytes iodinated polypeptides other than thyroglobulin and that one of the major iodinated polypeptides was the mature form of the lysosomal protease cathepsin D (CD), The detection of mature CD as an iodinated polypeptide suggested that a fraction of the lysosomally maturated enzyme was delivered to the apical plasma membrane where it became available for iodination, After labeling of thyrocytes with [S-35]methionine/cysteine overnight part of the mature CD was released into the culture medium. This was abolished by inhibiting maturation of CD with NH4Cl, indicating that mature CD appeared in the medium after its proteolytic maturation in an acidic compartment, Besides CD other soluble lysosomal polypeptides like the beta-N-acetylhexosaminidase and the sphingolipid-activating protein D (Sap D) were iodinated and partially secreted as mature polypeptides. In contrast, the membrane-associated lysosomal ceramidase was iodinated and partially secreted as immature single-chain enzyme and not as fully maturated two-chain enzyme,These data indicate that a portion of mature CD and other soluble lysosomal enzymes is delivered from lysosomes to the cell surface whereas come membrane-associated enzymes from the terminal lysosomal compartment are efficiently excluded from this process.
机译：甲状腺细胞因其能产生甲状腺激素的甲状腺球蛋白的能力而闻名。在完整的甲状腺中，碘化过程几乎完全在甲状腺上皮细胞的顶质膜上进行。在这里，我们显示新鲜分离的甲状腺细胞碘化了除甲状腺球蛋白以外的多肽，并且主要碘化多肽之一是溶酶体的成熟形式蛋白酶组织蛋白酶D（CD），检测到成熟的CD为碘化多肽，表明一部分溶酶体成熟的酶被递送至顶端质膜，可用于碘化，用[S-35]蛋氨酸标记了甲状腺细胞后半胱氨酸过夜将成熟CD的一部分释放到培养基中。通过用NH4Cl抑制CD的成熟来消除这种情况，这表明在CD的蛋白水解成熟后，成熟的CD出现在培养基中，除了CD以外，其他可溶性溶酶体多肽如β-N-乙酰基己糖胺酶和鞘脂激活蛋白D（Sap D）被碘化并部分分泌为成熟多肽。相比之下，膜相关的溶酶体神经酰胺酶碘化并部分分泌为未成熟的单链酶，而不是完全成熟的两链酶。这些数据表明，一部分成熟的CD和其他可溶性溶酶体酶从溶酶体传递至细胞表面，而来自末端溶酶体区室的膜相关酶则被有效地排除在该过程之外。

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