Blackshear P J, Nemenoff R A, Avruch J
Biochem J. 1983 Jul 15;214(1):11-9. doi: 10.1042/bj2140011.
Insulin, epidermal growth factor (EGF), platelet-derived growth factor, multiplication-stimulating activity and 10% foetal-calf serum each stimulated the phosphorylation of a cytosolic Mr-22000 acidic heat-stable protein in Swiss mouse 3T3-L1 adipocytes. Phosphorylation of this protein was not stimulated by isoprenaline or dibutyryl cyclic AMP. The effect of insulin was maximal (3-fold increase) by 10 min; half-maximal stimulation was observed at 70 pM-insulin. Both [32P]phosphoserine and [32P]phosphothreonine residues were present in the Mr-22000 protein after insulin- and growth-factor-stimulated phosphorylation, but no [32P]phosphotyrosine. The major site of insulin- and EGF-stimulated phosphorylation appeared to be a threonine residue, in contrast with previously studied insulin-stimulated phosphorylation of serine residues. Insulin treatment appeared to result in a shift of the protein toward the anode on isoelectric focusing. Insulin and EGF present simultaneously did not lead to phosphorylation beyond that seen with each hormone singly. We surmise that insulin, EGF and perhaps other growth factors may activate a common protein kinase or inhibit a common protein phosphatase in 3T3-L1 adipocytes which acts on the Mr-22000 protein.
胰岛素、表皮生长因子（EGF）、血小板衍生生长因子、增殖刺激活性因子和10%胎牛血清均能刺激瑞士小鼠3T3-L1脂肪细胞中一种分子量为22000的胞质酸性热稳定蛋白的磷酸化。异丙肾上腺素或二丁酰环磷酸腺苷不能刺激该蛋白的磷酸化。胰岛素作用10分钟时效果最佳（增加3倍）；在70 pM胰岛素浓度下观察到半最大刺激作用。胰岛素和生长因子刺激磷酸化后，Mr-22000蛋白中同时存在[32P]磷酸丝氨酸和[32P]磷酸苏氨酸残基，但不存在[32P]磷酸酪氨酸。与先前研究的胰岛素刺激丝氨酸残基磷酸化不同，胰岛素和EGF刺激磷酸化的主要位点似乎是苏氨酸残基。胰岛素处理似乎导致该蛋白在等电聚焦时向阳极移动。胰岛素和EGF同时存在时，磷酸化程度并不超过单独使用每种激素时的情况。我们推测，胰岛素、EGF以及其他可能的生长因子可能激活3T3-L1脂肪细胞中一种作用于Mr-22000蛋白的共同蛋白激酶，或抑制一种共同的蛋白磷酸酶。
