Nuche-Berenguer Bernardo, Jensen R T
Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-1804, USA.
Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-1804, USA.
Biochim Biophys Acta. 2015 Oct;1853(10 Pt A):2371-82. doi: 10.1016/j.bbamcr.2015.05.011. Epub 2015 May 12.
P-21-activated kinases (PAKs) are serine/threonine kinases comprising six isoforms divided in two groups, group-I (PAK1-3)/group-II (PAK4-6) which play important roles in cell cytoskeletal dynamics, survival, secretion and proliferation and are activated by diverse stimuli. However, little is known about PAKs ability to be activated by gastrointestinal (GI) hormones/neurotransmitters/growth-factors. We used rat pancreatic acini to explore the ability of GI-hormones/neurotransmitters/growth-factors to activate Group-I-PAKs and the signaling cascades involved. Only PAK2 was present in acini. PAK2 was activated by some pancreatic growth-factors [EGF, PDGF, bFGF], by secretagogues activating phospholipase-C (PLC) [CCK, carbachol, bombesin] and by post-receptor stimulants activating PKC [TPA], but not agents only mobilizing cellular calcium or increasing cyclic AMP. CCK-activation of PAK2 required both high- and low-affinity-CCK1-receptor-state activation. It was partially reduced by PKC- or Src-inhibition, but not with PI3K-inhibitors (wortmannin, LY294002) or thapsigargin. IPA-3, which prevents PAK2 binding to small-GTPases partially inhibited PAK2-activation, as well as reduced CCK-induced ERK1/2 activation and amylase release induced by CCK or bombesin. This study demonstrates pancreatic acini, possess only one Group-I-PAK, PAK2. CCK and other GI-hormones/neurotransmitters/growth-factors activate PAK2 via small GTPases (CDC42/Rac1), PKC and SFK but not cytosolic calcium or PI3K. CCK-activation of PAK2 showed several novel features being dependent on both receptor-activation states, having PLC- and PKC-dependent/independent components and small-GTPase-dependent/independent components. These results show that PAK2 is important in signaling cascades activated by numerous pancreatic stimuli which mediate their various physiological/pathophysiological responses and thus could be a promising target for the development of therapies in some pancreatic disorders such as pancreatitis.
p21活化激酶（PAKs）是丝氨酸/苏氨酸激酶，由六种亚型组成，分为两组，即I组（PAK1 - 3）/II组（PAK4 - 6），它们在细胞细胞骨架动力学、存活、分泌和增殖中发挥重要作用，并被多种刺激激活。然而，关于PAKs被胃肠（GI）激素/神经递质/生长因子激活的能力知之甚少。我们使用大鼠胰腺腺泡来探究GI激素/神经递质/生长因子激活I组PAKs的能力以及相关的信号级联反应。腺泡中仅存在PAK2。PAK2可被一些胰腺生长因子[表皮生长因子（EGF）、血小板衍生生长因子（PDGF）、碱性成纤维细胞生长因子（bFGF）]、激活磷脂酶C（PLC）的促分泌剂[胆囊收缩素（CCK）、卡巴胆碱、蛙皮素]以及激活蛋白激酶C（PKC）的受体后刺激剂[佛波酯（TPA）]激活，但不能被仅动员细胞内钙或增加环磷酸腺苷（cAMP）的试剂激活。CCK对PAK2的激活需要高亲和力和低亲和力CCK1受体状态的激活。它可被PKC或Src抑制部分降低，但PI3K抑制剂（渥曼青霉素、LY294002）或毒胡萝卜素对其无影响。IPA - 3可阻止PAK2与小GTP酶结合，部分抑制PAK2的激活，同时也降低了CCK诱导的细胞外信号调节激酶1/2（ERK1/2）激活以及CCK或蛙皮素诱导的淀粉酶释放。本研究表明，胰腺腺泡仅拥有一种I组PAK，即PAK2。CCK和其他GI激素/神经递质/生长因子通过小GTP酶（细胞分裂周期蛋白42/小G蛋白Rac1）、PKC和Src家族激酶（SFK）激活PAK2，但不通过胞质钙或PI3K激活。CCK对PAK2的激活表现出几个新特点，依赖于两种受体激活状态，具有PLC和PKC依赖/非依赖成分以及小GTP酶依赖/非依赖成分。这些结果表明，PAK2在由多种胰腺刺激激活的信号级联反应中起重要作用，这些刺激介导了它们的各种生理/病理生理反应，因此可能是开发某些胰腺疾病（如胰腺炎）治疗方法的一个有前景的靶点。
