Hegazy M G, Schlender K K, Wilson S E, Reimann E M
Department of Biochemistry, Medical College of Ohio, Toledo 43699.
Biochim Biophys Acta. 1989 May 10;1011(2-3):198-204. doi: 10.1016/0167-4889(89)90210-3.
Several polycations were tested for their abilities to inhibit the activity of glycogen synthase kinase 3 (GSK-3). L-Polylysine was the most powerful inhibitor of GSK-3 with half-maximal inhibition of glycogen synthase phosphorylation occurring at approx. 100 nM. D-Polylysine and histone H1 were also inhibitory, but the concentration dependence was complex, and DL-polylysine was the least effective inhibitor. Spermine caused about 50% inhibition of GSK-3 at 0.7 mM and 70% inhibition at 4 mM. Inhibition of GSK-3 by L-polylysine could be blocked or reversed by heparin. A heat-stable polycation antagonist isolated from swine kidney cortex also blocked the inhibitory effect of L-polylysine on GSK-3 and blocked histone H1 stimulation of protein phosphatase 2A activity. Under the conditions tested, L-polylysine also inhibited GSK-3 catalyzed phosphorylation of type II regulatory subunit of cAMP-dependent protein kinase and a 63 kDa brain protein, but only slightly inhibited phosphorylation of inhibitor 2 or proteolytic fragments of glycogen synthase that contain site 3 (a + b + c). L-Polylysine at a concentration (200 nM) that caused nearly complete inhibition of GSK-3 stimulated casein kinase I and casein kinase II, but had virtually no effect on the catalytic subunit of cAMP-dependent protein kinase. These results suggest that polycations can be useful in controlling GSK-3 activity. Polycations have the potential to decrease the phosphorylation state of glycogen synthase at site 3, both by inhibiting GKS-3 as shown in this study and by stimulating the phosphatase reaction as shown previously (Pelech, S. and Cohen, P. (1985) Eur. J. Biochem. 148, 245-251).
对几种聚阳离子抑制糖原合酶激酶3（GSK - 3）活性的能力进行了测试。L - 聚赖氨酸是GSK - 3最有效的抑制剂，对糖原合酶磷酸化的半数最大抑制浓度约为100 nM。D - 聚赖氨酸和组蛋白H1也具有抑制作用，但浓度依赖性较为复杂，而DL - 聚赖氨酸是效果最差的抑制剂。精胺在0.7 mM时可导致约50%的GSK - 3抑制，在4 mM时抑制率达70%。L - 聚赖氨酸对GSK - 3的抑制作用可被肝素阻断或逆转。从猪肾皮质分离出的一种热稳定聚阳离子拮抗剂也能阻断L - 聚赖氨酸对GSK - 3的抑制作用，并阻断组蛋白H1对蛋白磷酸酶2A活性的刺激。在测试条件下，L - 聚赖氨酸还抑制了GSK - 3催化的环磷酸腺苷依赖性蛋白激酶II型调节亚基和一种63 kDa脑蛋白的磷酸化，但仅轻微抑制了抑制剂2或含有位点3（a + b + c）的糖原合酶蛋白水解片段的磷酸化。浓度为200 nM的L - 聚赖氨酸几乎完全抑制了GSK - 3刺激的酪蛋白激酶I和酪蛋白激酶II，但对环磷酸腺苷依赖性蛋白激酶的催化亚基几乎没有影响。这些结果表明聚阳离子可用于控制GSK - 3的活性。聚阳离子有可能降低糖原合酶位点3的磷酸化状态，一方面如本研究所示通过抑制GKS - 3，另一方面如先前所示通过刺激磷酸酶反应（Pelech, S.和Cohen, P.（1985）Eur. J. Biochem. 148, 245 - 251）。
