Garzotto M, White-Jones M, Jiang Y, Ehleiter D, Liao W C, Haimovitz-Friedman A, Fuks Z, Kolesnick R
Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Cancer Res. 1998 May 15;58(10):2260-4.
Protein kinase C (PKC) activation is often antiapoptotic, although in a few cell types PKC initiates apoptosis by an unknown mechanism. Recent investigations showed that activation of PKC alpha by 12-O-tetradecanoylphorbol 13-acetate (TPA) induced apoptosis in LNCaP prostate cancer cells. The present studies examine the mechanism of this effect and show that de novo ceramide generation through the enzyme ceramide synthase is required. TPA induced rapid ceramide generation, which was detectable by 1 h and increased linearly for 12 h. TPA-induced apoptosis was measurable by 12 h and was progressive for 48 h. Investigations into the mechanism of TPA-induced ceramide generation revealed that acid and neutral sphingomyelinase activities were not enhanced. However, TPA induced an increase in ceramide synthase activity that persisted for at least 16 h. Treatment with fumonisin B1, a specific natural inhibitor of ceramide synthase, abrogated both ceramide production and TPA-induced apoptosis. Ceramide analogues bypassed fumonisin B1 inhibition to initiate apoptosis directly. Thus, ceramide appears to be a necessary signal for TPA-induced apoptosis in LNCaP cells. This represents the first description of a pathway by which PKC may signal apoptosis.
蛋白激酶C（PKC）激活通常具有抗凋亡作用，尽管在少数细胞类型中，PKC通过未知机制引发凋亡。最近的研究表明，12 - O - 十四烷酰佛波醇13 - 乙酸酯（TPA）激活PKCα可诱导LNCaP前列腺癌细胞凋亡。本研究探讨了这种效应的机制，并表明需要通过神经酰胺合酶从头生成神经酰胺。TPA诱导快速产生神经酰胺，1小时即可检测到，并在12小时内呈线性增加。TPA诱导的凋亡在12小时时可检测到，并在48小时内持续进展。对TPA诱导神经酰胺生成机制的研究表明，酸性和中性鞘磷脂酶活性并未增强。然而，TPA诱导神经酰胺合酶活性增加，且这种增加持续至少16小时。用伏马菌素B1（一种神经酰胺合酶的特异性天然抑制剂）处理可消除神经酰胺生成和TPA诱导的凋亡。神经酰胺类似物可绕过伏马菌素B1的抑制作用直接引发凋亡。因此，神经酰胺似乎是TPA诱导LNCaP细胞凋亡的必要信号。这是对PKC可能发出凋亡信号途径的首次描述。
