Nematode chondroitin polymerizing factor showing cell-/organ-specific expression is indispensable for chondroitin synthesis and embryonic cell division
Nematode chondroitin polymerizing factor showing cell-/organ-specific expression is indispensable for chondroitin synthesis and embryonic cell division
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DOI：
10.1074/jbc.m409615200
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发表时间：
2004-12-17
影响因子：
4.8
通讯作者：
Sugahara, K
中科院分区：
文献类型：
--
作者：
Izumikawa, T;Kitagawa, H;Sugahara, K
当人软骨素合酶（ChSy）与人软骨素聚合因子（ChPF）共表达时，软骨素聚合首次在体外得到证实，后者与 ChSy 同源，但几乎没有糖基转移酶活性。为了分析软骨素的生物学功能，最近克隆了人 ChSy (sqv-5) 的秀丽隐杆线虫直系同源物，并通过 RNA 介导的干扰 (RNAi) 和缺失诱变来消除其产物的表达。软骨素合成的阻断导致早期胚胎发生中胞质分裂的缺陷，最终细胞分裂停止。在这里，我们克隆了秀丽隐杆线虫中人类 ChPF 的直系同源物 PAR2.4。尽管该基因产物的糖基转移酶活性很小，但当 PAR2.4 与 cChSy 在体外共表达时，在哺乳动物的情况下证实了软骨素聚合。通过 RNAi 耗尽 PAR2.4 后观察到的蠕虫表型（包括胞质分裂的逆转）与 cChSy (sqv-5)-RNAi 表型非常相似。因此，除了cChSy之外，PAR2.4对于秀丽隐杆线虫软骨素的生物合成也是不可或缺的，两者在体内协同合成软骨素。在Seam细胞中观察到PAR2.4蛋白的表达，该细胞可以充当早期胚胎谱系中的神经干细胞。在从 L3 到青年阶段生长的性腺臂的外阴和远端细胞中也检测到了该表达。这些发现与软骨素参与外阴器官发生和性腺成熟的观点一致，也表明软骨素参与远端细胞迁移和神经发育。
Chondroitin polymerization was first demonstrated in vitro when human chondroitin synthase (ChSy) was coexpressed with human chondroitin polymerizing factor (ChPF), which is homologous to ChSy but has little glycosyltransferase activity. To analyze the biological function of chondroitin, the Caenorhabditis elegans ortholog of human ChSy (sqv-5) was recently cloned, and the expression of its product was depleted by RNA-mediated interference (RNAi) and deletion mutagenesis. Blocking of chondroitin synthesis resulted in defects of cytokinesis in early embryogenesis, and eventually, cell division stopped. Here, we cloned the ortholog of human ChPF in C. elegans, PAR2.4. Despite little glycosyltransferase activity of the gene product, chondroitin polymerization was demonstrated as in the case of mammals when PAR2.4 was coexpressed with cChSy in vitro. The worm phenotypes including the reversion of cytokinesis, observed after the depletion of PAR2.4 by RNAi, were very similar to the cChSy (sqv-5)-RNAi phenotypes. Thus, PAR2.4 in addition to cChSy is indispensable for the biosynthesis of chondroitin in C. elegans, and the two cooperate to synthesize chondroitin in vivo. The expression of the PAR2.4 protein was observed in seam cells, which can act as neural stem cells in early embryonic lineages. The expression was also detected in vulva and distal tip cells of the growing gonad arms from L3 through to the young adult stage. These findings are consistent with the notion that chondroitin is involved in the organogenesis of the vulva and maturation of the gonad and also indicative of an involvement in distal tip cell migration and neural development.