Design and application of a fluorogenic assay for monitoring inflammatory caspase activity

Interleukin-1β converting enzyme (ICE): A comprehensive review on discovery and development of caspase-1 inhibitors

Caspase-1 is a critical mediator of the inflammatory process by activating various pro-inflammatory cytokines such as pro-IL-1β, IL-18 and IL-33. Uncontrolled activation of caspase-1 leads to various cytokines-mediated diseases. Thus, inhibition of Caspase-1 is considered therapeutically beneficial to halt the progression of such diseases. Currently, rilonacept, canakinumab and anakinra are in use for caspase-1-mediated autoinflammatory diseases. However, the poor pharmacokinetic profile of these peptides limits their use as therapeutic agents. Therefore, several peptidomimetic inhibitors have been developed, but only a few compounds (VX-740, VX-765) have advanced to clinical trials; because of their toxic profile. Several small molecule inhibitors have also been progressing based on the three-dimensional structure of caspase-1. However there is no successful candidate available clinically. In this perspective, we highlight the mechanism of caspase-1 activation, its therapeutic potential as a disease target and potential therapeutic strategies targeting caspase-1 with their limitations.

Coumarin as a structural component of substrates and probes for serine and cysteine proteases

Coumarins represent well-established structures to introduce fluorescence into tool compounds for biochemical investigations. They are valued for their small size, chemical stability and accessibility as well as their tunable photochemical properties. As components of fluorophore/quencher pairs or FRET donor/acceptor pairs, coumarins have frequently been applied in substrate mapping approaches for serine and cysteine proteases. This review also focuses on the incorporation of coumarins into the side chain of amino acids and the exploitation of the resulting fluorescent amino acids for the positional profiling of protease substrates. The protease-inhibiting properties of certain coumarin derivatives and the utilization of coumarin moieties to assemble activity-based probes for serine and cysteine proteases are discussed as well.

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Coumarins represent well-established structures to introduce fluorescence into tool compounds for biochemical investigations.

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They are valued for their small size, chemical stability and accessibility as well as their tunable photochemical properties.

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Coumarins are components of fluorophore/quencher pairs or FRET donor/acceptor pairs in substrate mapping of proteases.

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Coumarins have been incorporated into amino acids side chains to be used for the positional profiling of protease substrates.

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Coumarins have protease-inhibiting properties and are used for activity-based probes for serine and cysteine proteases.

Caspase 1 activity influences juvenile Batten disease (CLN3) pathogenesis

Juvenile Neuronal Ceroid Lipofuscinosis (JNCL) is an autosomal recessive lysosomal storage disease caused by loss-of-function mutations in CLN3. Symptoms appear between 5 and 10 years of age, beginning with blindness and seizures, followed by progressive cognitive and motor decline, and premature death. Glial activation and impaired neuronal activity are early signs of pathology in the Cln3^Δex7/8 mouse model of JNCL, whereas neuron death occurs much later in the disease process. We previously reported that Cln3^Δex7/8 microglia are primed toward a pro-inflammatory phenotype typified by exaggerated caspase 1 inflammasome activation and here we extend those findings to demonstrate heightened caspase activity in the Cln3^Δex7/8 mouse brain. Based on the ability of caspase 1 to cleave a large number of substrates that have been implicated in JNCL pathology, we examined the functional implications of caspase 1 inflammasome activity by crossing Cln3^Δex7/8 and caspase 1-deficient mice to create Cln3^Δex7/8 /Casp-1^-/- animals. Caspase 1 deletion influenced motor behavior deficits and astrocyte activation in the context of CLN3 mutation, since both were significantly reversed in Cln3^Δex7/8 /Casp-1^-/- mice, with phenotypes approaching that of wild-type animals. We also report a progressive age-dependent reduction in whisker length in Cln3^Δex7/8 mice that was partially caspase 1-dependent. However, not all CLN3 phenotypes were reversed following caspase 1 deletion, since no significant differences in lysosomal accumulation or microglial activation were observed between Cln3^Δex7/8 and Cln3^Δex7/8 /Casp-1^-/- mice. Although the molecular targets of aberrant caspase 1 activity in the context of CLN3 mutation remain to be identified, our studies suggest that caspase 1 may represent a potential therapeutic target to mitigate some attributes of CLN3 disease. This article is part of the Special Issue "Lysosomal Storage Disorders".