Huang R, Lian J P, Robinson D, Badwey J A
Arthritis Unit, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
Mol Cell Biol. 1998 Dec;18(12):7130-8. doi: 10.1128/MCB.18.12.7130.
Activation of the p21-activated protein kinases (Paks) was compared in neutrophils stimulated with a wide variety of agonists that bind to receptors coupled to heterotrimeric G proteins. Neutrophils stimulated with sulfatide, a ligand for the L-selectin receptor, or the chemoattractant fMet-Leu-Phe (fMLP), platelet-activating factor, leukotriene B4, interleukin-8, or the chemokine RANTES exhibited a rapid and transient activation of the 63- and 69-kDa Paks. These kinases exhibited maximal activation with each of these agonists within 15 s followed by significant inactivation at 3 min. In contrast, neutrophils treated with the chemoattractant and anaphylatoxin C5a exhibited a prolonged activation (>15 min) of these Paks even though the receptor for this ligand may activate the same overall population of complex G proteins as the fMLP receptor. Addition of fMLP to neutrophils already stimulated with C5a resulted in the inactivation of the 63- and 69-kDa Paks. Optimal activation of Paks could be observed at concentrations of these agonists that elicited only shape changes and chemotaxis in neutrophils. While all of the agonists listed above triggered quantitatively similar activation of the 63- and 69-kDa Paks, fMLP was far superior to the other stimuli in triggering activation of the c-Jun N-terminal kinase (JNK) and the p38 mitogen-activated protein kinase (MAPK). These data indicate that separate signals are required for activation and inactivation of Paks and that, in contrast to other cell types, activated Pak does not trigger activation of JNK or p38-MAPK in neutrophils. These results are consistent with the recent hypothesis that G-protein-coupled receptors may initiate signals independent of those transmitted by the alpha and betagamma subunits of complex G proteins.
在受到多种与异源三聚体G蛋白偶联的受体结合的激动剂刺激的中性粒细胞中，对p21激活蛋白激酶（Paks）的激活情况进行了比较。用硫苷脂（L-选择素受体的配体）、趋化因子N-甲酰甲硫氨酰-亮氨酰-苯丙氨酸（fMet-Leu-Phe，fMLP）、血小板活化因子、白三烯B4、白细胞介素-8或趋化因子调节激活正常T细胞表达和分泌因子（RANTES）刺激中性粒细胞时，63 kDa和69 kDa的Paks会迅速且短暂地激活。这些激酶在15秒内被每种激动剂激活至最大值，随后在3分钟时显著失活。相比之下，用趋化因子和过敏毒素C5a处理的中性粒细胞，这些Paks会出现长时间激活（>15分钟），尽管该配体的受体可能与fMLP受体激活相同总体的复合G蛋白。向已经用C5a刺激的中性粒细胞中添加fMLP会导致63 kDa和69 kDa的Paks失活。在这些激动剂的浓度下可观察到Paks的最佳激活，此时这些浓度仅在中性粒细胞中引发形态变化和趋化作用。虽然上述所有激动剂在数量上引发了63 kDa和69 kDa的Paks类似的激活，但fMLP在触发c-Jun氨基末端激酶（JNK）和p38丝裂原活化蛋白激酶（MAPK）的激活方面远优于其他刺激物。这些数据表明，Paks的激活和失活需要不同的信号，并且与其他细胞类型不同，激活的Pak不会在中性粒细胞中触发JNK或p38-MAPK的激活。这些结果与最近的假说一致，即G蛋白偶联受体可能启动独立于复合G蛋白的α和βγ亚基所传递信号的信号。
