Huang Y, Chen H L
Department of Biochemistry, Shanghai Medical University.
Shi Yan Sheng Wu Xue Bao. 1997 Dec;30(4):383-9.
In order to elucidate the relation between cell signal transduction and cell differentiation, the effect of two differentiation inducers--all trans-retinoic acid (ATRA) and 13 cis-retinoic acid (13 cis-RA) on the specific activities (nmol/hr.mg protein) of phosphatidyl choline specific phospholipase D (PC-PLD) in 7721 human hepatocarcinoma cell line was studied. It was found that ATRA and 13 cis-RA increased the specific activities of membrane bound PC-PLD on 2nd and 4th day of cell culture respectively. If the PC-PLD activities were calculated as activity per bottle cells, the effect of ATRA on the 2nd day was also higher than that of 13 cis-RA, while the reverse was true on the 4th day, revealing a postponed effect of 13 cis-RA as compared with ATRA. The increase of PC-PLD was higher when the culture medium was refreshed every day than that when the medium was unrefreshed, suggesting that a factor might be existed in the fresh medium which could enhance the stimulating effect of retinoic acids on PC-PLD. The effect of ATRA on PC-PLD specific activity were higher on 2nd day than that on 4th day, owing to the accelerated proliferation of the cells on 4th day, leading to the increase of protein contents and decrease of the enzyme specific activity calculated on the base of protein contents. Whereas, the effect of 13 cis-RA on PC-PLD specific activity were higher on 4th day than that on 2nd day, because the increase of enzyme activity was higher than the increase of protein contents on 4th day. The relation between the elevation of PC-PLD and protein kinases was further studied and discovered that ATRA decreased both the specific activities of membrane bound and cytosolic protein kinase C (PKC) as well as tyrosine protein kinase (TPK) either in 2nd or 4th day of cell culture, which indicated that the increasing effect of ATRA on membrane bound PC-PLD was not resulted from the stimulating effect of PKC and TPK on PC-PLD, and its mechanism remains to be further investigated.
为阐明细胞信号转导与细胞分化之间的关系，研究了两种分化诱导剂——全反式维甲酸（ATRA）和13顺式维甲酸（13 cis-RA）对7721人肝癌细胞系中磷脂酰胆碱特异性磷脂酶D（PC-PLD）比活性（nmol/小时·毫克蛋白）的影响。结果发现，ATRA和13 cis-RA分别在细胞培养的第2天和第4天增加了膜结合PC-PLD的比活性。若以每瓶细胞的活性计算PC-PLD活性，ATRA在第2天的作用也高于13 cis-RA，而在第4天则相反，这表明13 cis-RA与ATRA相比有延迟效应。每天更换培养基时PC-PLD的增加高于不更换培养基时，这表明新鲜培养基中可能存在一种因子，可增强维甲酸对PC-PLD的刺激作用。ATRA对PC-PLD比活性的影响在第2天高于第4天，这是由于第4天细胞增殖加速，导致蛋白含量增加，基于蛋白含量计算的酶比活性降低。然而，13 cis-RA对PC-PLD比活性的影响在第4天高于第2天，因为第4天酶活性的增加高于蛋白含量的增加。进一步研究了PC-PLD升高与蛋白激酶之间的关系，发现ATRA在细胞培养的第2天或第4天均降低了膜结合和胞质蛋白激酶C（PKC）以及酪氨酸蛋白激酶（TPK）的比活性，这表明ATRA对膜结合PC-PLD的增强作用并非源于PKC和TPK对PC-PLD的刺激作用，其机制仍有待进一步研究。
