Martelli A M, Gilmour R S, Manzoli F A, Cocco L
Istituto di Anatomia Umana Normale, Bologna, Italy.
Biochem Biophys Res Commun. 1990 Nov 30;173(1):149-55. doi: 10.1016/s0006-291x(05)81034-4.
As a step towards the elucidation of the role played by nuclear polyphosphoinositides, we have investigated the effect of exogenous calcium free inositol (1,4,5)-trisphosphate on the in vitro phosphorylation of proteins in nuclei prepared from Swiss 3T3 cells treated with bombesin and insulin-like growth factor I. When present in combination with phosphatidylserine, inositol (1,4,5)-trisphosphate enhanced the phosphorylation of two nuclear proteins, Mr 21,000 and 31,000, as well as of exogenous histone H1, to the same extent as a combination of phosphatidylserine and diacylglycerol. Inositol (1,4,5)-trisphosphate alone had no effect. This stimulation could be abolished by the protein kinase C inhibitor sphingosine and by EGTA, while could be restored by a combination of phosphatidylserine and exogenous Ca+(+) ions. These results raise the possibility that inositol (1,4,5)-trisphosphate is capable of liberating Ca+(+) ions from a nuclear store thus stimulating protein kinase C activity.
作为阐明核多磷酸肌醇所起作用的一个步骤，我们研究了外源无钙肌醇（1,4,5）-三磷酸对用铃蟾肽和胰岛素样生长因子I处理的瑞士3T3细胞制备的细胞核中蛋白质体外磷酸化的影响。当与磷脂酰丝氨酸结合存在时，肌醇（1,4,5）-三磷酸增强了两种核蛋白（分子量分别为21,000和31,000）以及外源组蛋白H1的磷酸化，其程度与磷脂酰丝氨酸和二酰基甘油的组合相同。单独的肌醇（1,4,5）-三磷酸没有作用。这种刺激可被蛋白激酶C抑制剂鞘氨醇和EGTA消除，而可被磷脂酰丝氨酸和外源Ca⁺⁺离子的组合恢复。这些结果增加了一种可能性，即肌醇（1,4,5）-三磷酸能够从核储存中释放Ca⁺⁺离子，从而刺激蛋白激酶C活性。
