Chow S C, Sisfontes L, Jondal M, Björkhem I
Department of Immunology, Karolinska Institute, Stockholm, Sweden.
Biochim Biophys Acta. 1991 May 17;1092(3):358-66. doi: 10.1016/s0167-4889(97)90013-6.
The effect of modifying fatty acyl composition of cellular membrane phospholipids on receptor-mediated intracellular free Ca2+ concentration ([Ca2+]i) increase was investigated in a leukemic T cell line (JURKAT). After growing for 72 h in medium supplemented with unsaturated fatty acids (UFAs) and alpha-tocopherol, the fatty acyl composition of membrane phospholipids in JURKAT cells was extensively modified. Each respective fatty acid supplemented in the culture medium was readily incorporated into phosphatidylinositol, phosphatidylserine, phosphatidylethanolamine and phosphatidylcholine in the JURKAT cells. The total n-6 fatty acyl content was markedly reduced in phosphatidylinositol and phosphatidylcholine of cells grown in the presence of n-3 fatty acids (alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid). Conversely, in the presence of n-6 fatty acids (linoleic acid and arachidonic acid), the total n-3 fatty acyl content was reduced in all the phospholipids examined. In n-3 and n-6 polyunsaturated fatty acid (PUFA) modified JURKAT cells, the total n-9 monounsaturated fatty acyl content in the phospholipids were markedly reduced. Changing the fatty acyl composition of membrane phospholipids in the JURKAT cells appears to have no affect on the presentation of the T cell receptor/CD3 complex or the binding of anti-CD3 antibodies (OKT3) to the CD3 complex. However, the peak increase in [Ca2+]i and the prolonged sustained phase elicited by OKT3 activation were suppressed in n-3 and n-6 PUFA but not in n-9 monounsaturated fatty acid modified cells. In Ca2+ free medium, OKT3-induced transient increase in [Ca2+]i representing Ca2+ release from the inositol 1,4,5-trisphosphate-sensitive Ca2+ stores, were similar in control and UFA modified cells. Using Mn2+ entry as an index of plasma membrane Ca2+ permeability, the rate of fura-2 fluorescence quenching as a result of Mn2+ influx stimulated by OKT3 in n-9 monounsaturated fatty acid modified cells was similar to control cells, but the rates in n-3 and n-6 PUFA modified cells were significantly lower. These results suggest that receptor-mediated Ca2+ influx in JURKAT cells is sensitive to changes in the fatty acyl composition of membrane phospholipids and monounsaturated fatty acids appears to be important for the maintenance of a functional Ca2+ influx mechanism.
在白血病T细胞系（JURKAT）中研究了细胞膜磷脂脂肪酸酰基组成的改变对受体介导的细胞内游离钙离子浓度（[Ca2+]i）升高的影响。在添加了不饱和脂肪酸（UFA）和α-生育酚的培养基中培养72小时后，JURKAT细胞中膜磷脂的脂肪酸酰基组成发生了广泛改变。培养基中添加的每种脂肪酸都很容易掺入JURKAT细胞的磷脂酰肌醇、磷脂酰丝氨酸、磷脂酰乙醇胺和磷脂酰胆碱中。在n-3脂肪酸（α-亚麻酸、二十碳五烯酸和二十二碳六烯酸）存在下生长的细胞的磷脂酰肌醇和磷脂酰胆碱中，总n-6脂肪酸酰基含量显著降低。相反，在n-6脂肪酸（亚油酸和花生四烯酸）存在下，所有检测的磷脂中总n-3脂肪酸酰基含量均降低。在n-3和n-6多不饱和脂肪酸（PUFA）修饰的JURKAT细胞中，磷脂中的总n-9单不饱和脂肪酸酰基含量显著降低。JURKAT细胞中膜磷脂脂肪酸酰基组成的改变似乎对T细胞受体/CD3复合物的表达或抗CD3抗体（OKT3）与CD3复合物的结合没有影响。然而，n-3和n-6 PUFA修饰的细胞中，OKT3激活引起的[Ca2+]i峰值升高和延长的持续期受到抑制，而n-9单不饱和脂肪酸修饰的细胞中则没有。在无钙培养基中，OKT3诱导的[Ca2+]i瞬时升高代表肌醇1,4,5-三磷酸敏感的钙库释放钙，在对照细胞和UFA修饰的细胞中相似。以Mn2+内流作为质膜Ca2+通透性的指标，n-9单不饱和脂肪酸修饰的细胞中OKT3刺激引起的Mn2+内流导致的fura-2荧光淬灭速率与对照细胞相似，但n-3和n-6 PUFA修饰的细胞中的速率显著较低。这些结果表明，JURKAT细胞中受体介导的Ca2+内流对膜磷脂脂肪酸酰基组成的变化敏感，单不饱和脂肪酸似乎对维持功能性Ca2+内流机制很重要。
