Zinc-mediated Allosteric Inhibition of Caspase-6

Velázquez-Delgado, Elih M.; Hardy, James L.

doi:10.1074/jbc.m112.397752

Cited by 65 publications

(97 citation statements)

References 70 publications

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“…While it is clear that zinc selectively inhibits caspase-3, -7, and -8 in standard caspase assay conditions (Figure 2) as well as caspase-6, 33 the affinity can not be accurately measured unless the zinc-binding properties of every component of the solution are both understood and accounted for. In addition, zinc-mediated inhibition is only biologically relevant at certain affinities.…”

Section: Resultsmentioning

confidence: 99%

“…Under zinc-buffering conditions there was a significant shift in IC 50 values relative to the unbuffered conditions (Table 1). Caspase-6, which is known to bind zinc at an exosite, showed the largest shift in binding affinity (IC 50 of 4.5 μM (unbuffered) 33 to 2 nM (buffered)). Caspase-3, -7, and -8 were then assayed, under buffered conditions, at various concentrations of zinc to investigate the mechanism of inhibition (Figure S2).…”

Section: Resultsmentioning

confidence: 99%

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Multiple Mechanisms of Zinc-Mediated Inhibition for the Apoptotic Caspases-3, -6, -7, and -8

et al. 2018

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Zinc is emerging as a widely used and important biological regulatory signal. Cellular zinc levels are tightly regulated by a complex array of zinc importer and exporters to control processes such as apoptotic cell death. While caspase inhibition by zinc has been reported previously, the reported inhibition constants were too weak to suggest a critical biological role for zinc-mediated inhibition. In this work we have adopted a method of assessing available zinc. This allowed assessment of the accurate inhibition constants for apoptotic caspases, caspase-3, -6, -7 and -8. Each of these caspases are inhibited by zinc at intracellular levels, however, with widely differing inhibition constants and different zinc binding stoichiometries. Caspase -3, -6 and -8 appear to be constitutively inhibited by typical zinc levels and this inhibition must be lifted to allow activation. The inhibition constant for caspase-7 (76 nM) is much weaker than for the other apoptotic caspases (2.6–6.9 nM) suggesting that caspase-7 is not inactivated by normal zinc concentrations but can be inhibited under conditions of zinc stress. Caspase-3, -7, and -8 were found to bind three, one, and two zincs respectively. In each of these caspases, zinc was present in the active site, in contrast to caspase-6, which binds one zinc allosterically. The most notable new mechanism to emerge from this work is for zinc-mediated inhibition of caspase-8. Zinc binds caspase-8 directly at the active site and at a second site. Zinc binding inhibits formation of the caspase-8 dimer, the activated form of the enzyme. Together these findings suggest that zinc plays a critical role in regulation of apoptosis by direct inactivation of caspases, in a manner that is unique for each caspase.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Multiple Mechanisms of Zinc-Mediated Inhibition for the Apoptotic Caspases-3, -6, -7, and -8

et al. 2018

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“…Influence of zinc on limiting free radicals will be discussed in the following section. With regards to the direct effect zinc has on caspases, many studies established the inhibitory role of zinc on apoptotic caspases 3, 6, 7,8 and 9 [49][50][51]. Caspase-3 is particularly interesting due to its dominant role in the apoptotic pathway.…”

Section: A Nf-κb and Other Signalling Pathwaymentioning

confidence: 99%

Zinc in Infection and Inflammation

Gammoh¹,

Rink²

2017

Preprint

126

139

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Abstract:Micronutrient homeostasis is a key factor in maintaining a healthy immune system. Zinc is an essential micronutrient that is involved in the regulation of the innate and adaptive immune responses. The main cause of zinc deficiency is malnutrition. Zinc deficiency leads to cell-mediated immune dysfunctions among other manifestations. Consequently, such dysfunctions lead to a worse outcome in the response towards bacterial infection and sepsis. For instance, zinc is an essential component of the pathogen-eliminating signal transduction pathways leading to neutrophil extracellular traps formation, as well as inducing cell-mediated immunity over humoral immunity by regulating specific factors or differentiation. Additionally, zinc deficiency plays a role in inflammation, mainly elevating inflammatory response as well as damage to host tissue. Zinc is involved in the modulation of the proinflammatory response by targeting Nuclear Factor Kappa B, a transcription factor that is the master regulator of proinflammatory responses. It is also involved in controlling oxidative stress and regulating inflammatory cytokines. Zinc plays an intricate function during an immune response and its homeostasis is critical for sustaining proper immune function. This review will summarize the latest findings concerning the role of this micronutrient during the course of infections and inflammatory response and how the immune system modulates zinc depending on different stimuli.

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Section: Discussionmentioning

confidence: 99%

“…Nonetheless, several other laboratories reported the regulation of other cysteine proteases by metal ions, including zinc (44)(45)(46)(47)(48). For example, human apoptotic caspases, a family of cysteine proteases involved in apoptosis, are a recognized model for studying zinc-mediated inhibition of proteolytic activity (44,46,48). These studies revealed that the proteolytic activity of caspase 6 can indeed be inhibited by direct binding of zinc to an exosite distal to the active site (48), whereas caspase 9, which harbors two zinc binding sites, namely, an active site and an exosite, was shown to be inhibited to a greater extent following the biding of zinc to the active site that harbors the catalytic dyad 287 Cys and 237 His (44).…”

Section: Discussionmentioning

confidence: 99%

Metal-Mediated Modulation of Streptococcal Cysteine Protease Activity and Its Biological Implications

et al. 2014

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dStreptococcal cysteine protease (SpeB), the major secreted protease produced by group A streptococcus (GAS), cleaves both host and bacterial proteins and contributes importantly to the pathogenesis of invasive GAS infections. Modulation of SpeB expression and/or its activity during invasive GAS infections has been shown to affect bacterial virulence and infection severity. Expression of SpeB is regulated by the GAS CovR-CovS two-component regulatory system, and we demonstrated that bacteria with mutations in the CovR-CovS two-component regulatory system are selected for during localized GAS infections and that these bacteria lack SpeB expression and exhibit a hypervirulent phenotype. Additionally, in a separate study, we showed that expression of SpeB can also be modulated by human transferrin-and/or lactoferrin-mediated iron chelation. Accordingly, the goal of this study was to investigate the possible roles of iron and other metals in modulating SpeB expression and/or activity in a manner that would potentiate bacterial virulence. Here, we report that the divalent metals zinc and copper inhibit SpeB activity at the posttranslational level. Utilizing online metal-binding site prediction servers, we identified two putative metal-binding sites in SpeB, one of which involves the catalytic-dyad residues 47 Cys and 195 His. Based on our findings, we propose that zinc and/or copper availability in the bacterial microenvironment can modulate the proteolytic activity of SpeB in a manner that preserves the integrity of several other virulence factors essential for bacterial survival and dissemination within the host and thereby may exacerbate the severity of invasive GAS infections.

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Zinc-mediated Allosteric Inhibition of Caspase-6

Cited by 65 publications

References 70 publications

Multiple Mechanisms of Zinc-Mediated Inhibition for the Apoptotic Caspases-3, -6, -7, and -8

Multiple Mechanisms of Zinc-Mediated Inhibition for the Apoptotic Caspases-3, -6, -7, and -8

Zinc in Infection and Inflammation

Metal-Mediated Modulation of Streptococcal Cysteine Protease Activity and Its Biological Implications

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