发布: 2018年01月05日第8卷第1期 DOI: 10.21769/BioProtoc.2684 浏览次数: 6317
评审: Ivan ZanoniGuadalupe Ortiz-MuñozHenrique Borges da Silva
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Abstract
Oxidative inactivation of cysteine-dependent Protein Tyrosine Phosphatases (PTPs) by cellular reactive oxygen species (ROS) plays a critical role in regulating signal transduction in multiple cell types. The phosphatase activity of most PTPs depends upon a ‘signature’ cysteine residue within the catalytic domain that is maintained in the de-protonated state at physiological pH rendering it susceptible to ROS-mediated oxidation. Direct and indirect techniques for detection of PTP oxidation have been developed (Karisch and Neel, 2013). To detect catalytically active PTPs, cell lysates are treated with iodoacetyl-polyethylene glycol-biotin (IAP-biotin), which irreversibly binds to reduced (S-) cysteine thiols. Irreversible oxidation of SHP-1 after treatment of cells with pervanadate or H2O2 is detected with antibodies specific for the sulfonic acid (SO3H) form of the conserved active site cysteine of PTPs. In this protocol, we describe a method for the detection of the reduced (S-; active) or irreversibly oxidized (SO3H; inactive) form of the hematopoietic PTP SHP-1 in thymocytes, although this method is applicable to any cysteine-dependent PTP in any cell type.
Keywords: Reactive oxygen species (活性氧种类)Background
Reactive oxygen species (ROS) are generated by cellular NADPH oxidases and mitochondria. Most Protein Tyrosine Phosphatases (PTPs) contain a conserved catalytic cysteine with a low dissociation constant (pKa) that is highly susceptible to oxidation by ROS (Rudyk and Eaton, 2014). ROS-inactivation of PTPs plays an important role in regulating tyrosine-kinase-mediated signaling responses in numerous cell types. PTPs are rapidly oxidized in cells treated with the ROS H2O2 or the PTP inhibitor pervanadate (Huyer et al., 1997; Choi et al., 2017). Iodoacetyl-polyethylene glycol-biotin (IAP-biotin) selectively and irreversibly reacts with de-protonated (S-) cysteine thiols (Rudyk and Eaton, 2014). To label basal reduced (active) cellular PTPs, IAP-biotin is added at the time of cell lysis.
PTP active site cysteines can be oxidized by ROS to the sulfenic acid form (-SOH), which can then be converted into either sulfenylamide (-SN-) or cysteine disulfide (S-S) forms. Sulfenic acid, sulfenylamide and disulfide oxidized PTPs can be ‘re-activated’ by treatment with thiol reducing agents such as dithiothreitol (DTT) which convert the catalytic cysteine to the active (SH) state. PTP oxidation can be detected indirectly by a three-step method (irreversible alkylation of reduced active site cysteines with an alkylating agent followed by reduction of reversibly oxidized (SOH) active site cysteines with a reducing agent, then finally labeling of the newly formed cysteine thiols) (Weibrecht et al., 2007). This method for direct detection of reversibly oxidized PTPs is not widely used due to the fact that the sulfenic acid state is labile and transient (Karisch and Neel, 2013). PTP catalytic cysteines can also be progressively irreversibly ‘hyper-oxidized’ to the sulfinic (-SO2H) followed by the sulfonic (-SO3H) forms by higher concentrations of ROS or prolonged exposure to ROS. The availability of monoclonal antibodies specific for the sulfonic acid (-SO3H) form of the conserved active site of PTPs has provided a straightforward way to detect oxidized PTPs following treatment of cells with oxidizing agents (Persson et al., 2004). The susceptibility of PTPs in different cell populations to oxidation can be assessed by treatment of cells with oxidizing agents (varying the concentration of oxidizing agent and/or treatment time) followed by blotting of proteins from cell lysates after separation by SDS-PAGE with anti-oxidized-PTP mAb. Here, we describe methods used to detect either reduced (S-; active) or irreversibly oxidized (SO3H; inactive) SHP-1 in thymocytes.
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文章信息
版权信息
© 2018 The Authors; exclusive licensee Bio-protocol LLC.
如何引用
Choi, S. and Love, P. E. (2018). Detection of Intracellular Reduced (Catalytically Active) SHP-1 and Analyses of Catalytically Inactive SHP-1 after Oxidation by Pervanadate or H2O2. Bio-protocol 8(1): e2684. DOI: 10.21769/BioProtoc.2684.
分类
免疫学 > 免疫细胞功能 > 综合
生物化学 > 蛋白质 > 活性
细胞生物学 > 细胞信号传导 > 胞内信号传导
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