(*contributed equally to this work) 发布: 2016年12月20日第6卷第24期 DOI: 10.21769/BioProtoc.2073 浏览次数: 9055
评审: Alka MehraMarielle CavroisAnonymous reviewer(s)
Abstract
Activity-based probes (ABP) are small organic molecules that irreversibly bind to the active center of a specific enzyme family and may be coupled to a fluorophore or an affinity tag (Li et al., 2013). Here, we describe a method to pull-down active catalytic standard and immunoproteasome subunits in cell lysates using the biotinylated, proteasome-specific ABP Biotin-Epoxomicin (Bio-EP). Covalent labeling of the active catalytic subunits with Bio-EP is followed by a pull-down using streptavidin-coated beads. After elution from the beads, enriched subunits may be detected via Western blot, tandem mass spectrometry (Li et al., 2013), or alternative techniques.
Keywords: Activity-based probe (基于酶活性的探针)Background
The proteasome is a barrel-shaped, multicatalytic enzyme complex that is present in the nucleus and cytoplasm of eukaryotic cells. It is essential for protein degradation, including processing of antigenic peptides for MHC I presentation, and regulates many cellular processes (Kammerl and Meiners, 2016). In cells of hematopoietic origin, the standard (constitutive) proteasome is often replaced by the immunoproteasome (Meiners et al., 2014), which differs in the incorporation of the three distinct catalytically active β-subunits (Figure 1).
To study the molecular function of single catalytic subunits and to modulate physiological processes, the development of subunit-specific proteasome inhibitors is indispensable. Large progress has recently been made in this area by de Bruin et al. (2014). Specific immunoproteasome inhibitors have proven as potential drug candidates for the treatment of inflammatory and autoimmune disease. The inhibition of the immunoproteasome subunit β5i may alter cytokine production by activated monocytes and lymphocytes. In a mouse model of rheumatoid arthritis, this reversed signs of the disease (Muchamuel et al., 2009).
The protocol was developed in the context of a study that investigated the effects of selective inhibition of β5i on the polarization of alveolar macrophages (Chen et al., 2016). The activity-based pull-down of catalytic standard and immunoproteasome subunits using the pan-reactive ABP Bio-EP allowed us to confirm the specific inhibition of β5i by the inhibitor ONX-0914, previously developed by ONYX Pharmaceuticals.
The use of ABPs with alternative specificity may allow for activity-based pull-down of other enzyme families in a similar experimental approach.
Figure 1. Structure of the 20S standard and immunoproteasome. The 20S core particle of the proteasome consists of two stacked inner rings containing the β-subunits 1-7 of which β1, β2 and β5 exhibit proteolytic activity. The β-rings are flanked by two α-rings containing the α-subunits 1-7. In the immunoproteasome β1, β2 and β5 are replaced by β1i, β2i and β5i, respectively, which leads to altered proteolytic activity.
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文章信息
版权信息
© 2016 The Authors; exclusive licensee Bio-protocol LLC.
如何引用
Baumann, T., Vosyka, O., Florea, B. I., Overkleeft, H. S., Meiners, S. and Kammerl, I. E. (2016). Activity-based Pull-down of Proteolytic Standard and Immunoproteasome Subunits. Bio-protocol 6(24): e2073. DOI: 10.21769/BioProtoc.2073.
分类
生物化学 > 蛋白质 > 免疫检测
生物化学 > 蛋白质 > 活性
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