Kirkham P A, Takamatsu H H, Lam E W, Parkhouse R M
Department of Immunology, Institute for Animal Health, Pirbright, Surrey, United Kingdom.
J Immunol. 2000 Oct 1;165(7):3564-70. doi: 10.4049/jimmunol.165.7.3564.
Ceramide is a powerful regulator of cell fate, inducing either apoptosis or growth arrest. We have previously shown that an Ab to the gammadelta T cell-specific orphan receptor, WC1, is able to induce growth arrest in proliferating IL-2-dependent gammadelta T cells. We now show that this WC1-mediated growth arrest is associated with an increase in cellular ceramide, in the absence of any measurable changes in acidic/neutral sphingomyelinase activity. Moreover, cell-permeable analogues of ceramide also mimicked WC1-induced growth arrest along with an associated decrease in pocket protein expression and phosphorylation status. An important role for ceramide in WC1-induced growth arrest was confirmed by demonstrating that the specific ceramide synthase inhibitor fumonisin B1 blocked WC1-induced growth arrest and the associated molecular effects on the pocket proteins. Finally, we observed constitutive expression of both antiapoptotic factors bcl-2 and bcl-X, the former having increased expression upon WC1 stimulation. It is therefore proposed that ligation of WC1 leads to an accumulation in cellular ceramide through activation of ceramide synthase. This in turn results in a decreased overall expression of the pocket proteins pRb and p107, their hypophosphorylation, and an eventual growth arrest of the gammadelta T cell. To our knowledge, these results demonstrate for the first time that cell surface receptor-mediated ceramide synthase activation can affect cell fate through increases in cellular ceramide and provide further evidence that the orphan receptor WC1 regulates gammadelta T cell biology through a novel signaling pathway.
神经酰胺是细胞命运的强大调节因子，可诱导细胞凋亡或生长停滞。我们之前已经表明，一种针对γδT细胞特异性孤儿受体WC1的抗体能够诱导依赖白细胞介素-2的增殖性γδT细胞发生生长停滞。我们现在表明，这种WC1介导的生长停滞与细胞神经酰胺的增加有关，而酸性/中性鞘磷脂酶活性没有任何可测量的变化。此外，神经酰胺的细胞可渗透类似物也模拟了WC1诱导的生长停滞，同时伴有口袋蛋白表达和磷酸化状态的相关降低。通过证明特异性神经酰胺合酶抑制剂伏马菌素B1阻断了WC1诱导的生长停滞以及对口袋蛋白的相关分子效应，证实了神经酰胺在WC1诱导的生长停滞中的重要作用。最后，我们观察到抗凋亡因子bcl-2和bcl-X的组成性表达，前者在WC1刺激后表达增加。因此，有人提出WC1的连接通过神经酰胺合酶的激活导致细胞神经酰胺的积累。这反过来又导致口袋蛋白pRb和p107的总体表达降低、它们的低磷酸化以及γδT细胞最终的生长停滞。据我们所知，这些结果首次证明细胞表面受体介导的神经酰胺合酶激活可以通过细胞神经酰胺的增加来影响细胞命运，并提供了进一步的证据表明孤儿受体WC1通过一条新的信号通路调节γδT细胞生物学。
