MAPK 与 p38 MAPK
作为对外界物理和化学性质变化的响应,哺乳动物细胞激活有丝分裂原激活蛋白激酶 (MAPK) 的四个特征性亚家族:ERK1/2、JNK、p38 和 ERK5。其中 p38 MAPKs 是一类保守的丝氨酸-苏氨酸蛋白激酶,可被多种细胞外炎症因子 (如TNF-α, IL-1),细菌脂多糖 LPS,趋化因子以及紫外线等多种应激刺激激活。激活后的 p38 MAPK 通过调控下游多种酶及转录因子表达活性,从而对细胞功能进行调节。大量研究表明,p38 MAPK 活性对正常免疫和炎症反应至关重要。同时,在肿瘤发生以及缺血再灌注损伤中也起着重要作用。
MAPK经典激活途径
与 p38 MAPK 相关靶点
MAPK 经典激活途径是通过 MAPK 激酶激酶 (MAP3K)-MAPK 激酶 (MAP2K) 途径实现的。首先 MAP3K 被激活, 随后,激活的 MAP3K 能磷酸化并激活MAP2K,接下来,MAP2K 磷酸化 MAPK,使MAPK激活。当然,也存在与 MAP3K -MAP2K 无关的,非典型的自磷酸化激活途径。在p38 MAPK激活途径 (即其上游信号通路) 中,属于MAP3K 类如 MEKK1-4,Tpl2,MLKs,ASK1/2,DLK,TAK1,TAO1/2;属于MAP2K 类如 MKK3 和 MKK6 (有时是 MKK4,可激活 p38α)。
图1. p38 MAPK 激活后下游靶点分布
p38 MAPK 包含四种亚型,分别为 p38α (MAPK 14),p38β (MAPK 11),p38γ (MAPK 12),p38δ (MAPK 13)。它们具有不同的组织表达模式,p38α 在大多数细胞类型中以显著水平普遍表达,而其他 p38 亚型似乎以更具组织特异性的方式表达,如 p38β 在脑中表达较为丰富,p38γ 是在骨骼肌中,而 p38δ 则是在内分泌腺中。p38 MAPK 激活后,由其介导的下游磷酸化调节主要为两大类蛋白,一类为转录因子,如 p53,ATF2,Elk1,MEF2 和 C/EBPβ,另一类为蛋白激酶,包括 MK2 (也称为 MAPKAP2),MSK1,MNK1 和 MNK2。
图2. p38 MAPK 信号通路图
如何选择 p38 MAPK抑制剂 ?
由于 p38 MAPK 通路与众多疾病如典型的炎症,肿瘤相关疾病等。因此,阻断 p38 MAPK 可能为治疗许多疾病提供有效的治疗方法。在实际研究中,想通过抑制 p38 MAPK 通路进一步确定参与该疾病的蛋白或转录因子以及其表达,合适的抑制剂非常重要。然而,由于 p38 MAPK 通路涉及的靶标众多,因此不同的抑制剂的抑制机理不同。例如,有些抑制剂是通过抑制 p38 MAPK 的活性,有些抑制剂则是通过抑制 p38磷酸化。敲黑板,划重点,如不清楚这些抑制剂的机制,不包括其他因素的情况,最后很可能导致所购买的抑制剂达不到预期的检测效果。
p38 MAPK 的经典抑制剂
SB 203580 (RWJ 64809)
SB 203580 是最常见也是研究最多的选择性 p38α,p38β MAPK 抑制剂 (IC50: p38α=50 nM; p38β2=500 nM)。研究表明,SB 203580 可通过结合 ATP 结合袋来抑制 p38 MAPK催化活性。SB 203580 不会影响来自 p38 MAPK 上游的激活 (即不影响 p38 MAPK 的磷酸化)。而通过检测 MK2 和其底物热休克蛋白 27 (HSP27) 磷酸化的抑制,也证明 SB 203580 抑制 p38 MAPK 的活性。
SB 202190 同 SB 203580一样,也属于吡啶基咪唑化合物类,是可渗透细胞的p38α,p38βMAPK 抑制剂 (IC50: p38α=50 nM;p38β2=100 nM)。SB 202190 通过结合 ATP 结合袋 (Kd=38 nM) 来抑制 p38 MAPK 活性。在 LPS 处理的巨噬细胞中,SB 202190 通过抑制 p38 MAPK 通路下游特异性底物 MK2 磷酸化,从而影响 HSP27 活化。但与 SB 203580 有所不同,在某些情况下,SB 202190 也可抑制 p38 MAPK 的磷酸化。
BIRB796 (Doramapimod)
Doramapimod 是一种具有口服活性的高效泛 p38 MAPK 抑制剂 (IC50: p38α=38 nM; p38β=65 nM; p38γ=200 nM; p38δ=520 nM)。其抑制机制主要是与 ATP 位点相邻的位置结合,间接影响 ATP 位点的构象。BIRB796 与 p38 MAPK 或 JNK1/2 的结合会损害上游激酶 MKK6 或 MKK4 的磷酸化。BIRB796 阻断应激诱导的支架蛋白SAP97 的磷酸化,而 SAP97 是 p38γ 的生理学底物。此外,BIRB796 还抑制 B-Raf,IC50 分别为 83 nM。![](https://img1.dxycdn.com/2021/1018/656/8329111179973510153-14.jpg)
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Abbreviation
MAP3K: MAPK kinase kinase;
MAP2K: MAPK kinase;
MEKK: MAPK/ERK kinase kinase;
Tpl2: Tumourprogression loci 2;
MLK: Mixed LineageKinase;
ASK1: Apoptosis signal-regulating kinase 1;
DLK: Dual-leucine-zipper-bearing kinase;
TAK1: TGFβ-activated kinase 1;
TAO1/2: Thousand-and-one amino acid 1/2
ATF: Activating transcription factor;
Elk1: ETS Like-1 protein Elk-1;
MEF2: Myocyte enhancer factor 2;
C/EBPβ: CCAAT/enhancer binding protein (C/EBP) β;
MK2 (MAPKAP2): MAP kinase-activated protein kinase 2;
MSK: Mitogen- and stress-activated kinase;
MNK1: Mitogen-activated protein kinase-interacting kinase 1;
HSP27: Heatshock protein 27;
SAP97: Synapse-associated protein 97 1. Johnson GL, et al. Mitogen-activated proteinkinase pathways mediated by ERK, JNK, and p38 protein kinases. Science. 2002 Dec6;298(5600):1911-2.2. Wagner EF, et al. Signal integration by JNKand p38 MAPK pathways in cancer development.3.Hari SB, et al.Conformation-selective ATP-competitive inhibitors control regulatory interactions and noncatalyticfunctions of mitogen-activated protein kinases.Chem Biol. 2014 May22;21(5):628-35. 4. Lee JC, et al. Inhibitionof p38 MAP kinase as a therapeutic strategy. Immunopharmacology. 2000 May;47(2-3):185-201.5. Davies SP, et al. Specificity and mechanism ofaction of some commonly used protein kinase inhibitors. Biochem J. 2000Oct 1;351(Pt 1):95-105.6.Frantz B, et al. The activation state of p38 mitogen-activated protein kinasedetermines the efficiency of ATP competition for pyridinylimidazole inhibitor binding.Biochemistry. 1998Sep 29;37(39):13846-53.7. Fukunaga R, et al. MNK1, a new MAP kinase-activated proteinkinase, isolated by a novel expression screening method for identifying proteinkinase substrates.8. Fabian MA, et al. A small molecule-kinaseinteraction map for clinical kinase inhibitors. Nat Biotechnol. 2005Mar;23(3):329-36.9.Kuma Y, et al.BIRB796 inhibits all p38 MAPK isoforms in vitro andin vivo. J Biol Chem. 2005 May 20;280(20):19472-9.10.Wagner G, et al. Small molecularanti-cytokine agents. Med Res Rev. 2006Jan;26(1):1-62.11. Natarajan SR, et al. P38 MAP kinase inhibitors: evolution ofimidazole-based and pyrido-pyrimidin-2-one lead classes.11.Raingeaud J, et al. Pro-inflammatory cytokines and environmental stress cause p38 mitogen-activated protein kinaseactivation by dual phosphorylation on tyrosine and threonine.13. Kuliopulos A, et al. Effect of selective inhibition of the p38 MAPkinase pathway on platelet aggregation. ThrombHaemost. 2004Dec;92(6):1387-93. (VX-702)14.Hope HR, et al. Anti-inflammatory properties of a novel N-phenylpyridinone inhibitor of p38 mitogen-activated protein kinase:preclinical-to-clinical translation. J Pharmacol Exp Ther. 2009 Dec;331(3):882-95.15.Xing L, et al. Structuralbioinformatics-based prediction of exceptional selectivity of p38 MAP kinaseinhibitor PH-797804. Biochemistry. 2009 Jul 14;48(27):6402-11.16. Chaudhary O, et al. Inhibition of p38 MAPK in combination withART reduces SIV-induced immune activation and provides additional protection fromimmune system deterioration. PLoS Pathog. 2018 Aug 30;14(8):e1007268.17. Cicenas J, et al. JNK, p38, ERK,and SGK1 Inhibitors in Cancer. Cancers(Basel). 2017Dec 21;10(1). pii: E1.18. Goldstein DM, et al. Selective p38alpha inhibitors clinicallyevaluated for the treatment of chronic inflammatory J Med Chem. 2010 Mar 25;53(6):2345-53.disorders.19. Tony Navas,et al. Thep38α MAPK inhibitor SCIO-469 enhances the apoptotic and anti-proliferativeeffects of proteasome inhibitors MG132 and PS341 (Velcade) in multiple myelomacells. Cellular, Molecular, and Tumor Biology 65: Cell Surface Death Pathways I
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