What is Caspase?

Caspase, a portmanteau of cysteine-aspartic proteases, is an extensive family of proteases playing an instrumental role in programmed cell death (apoptosis), inflammation, and a series of other vital physiological and pathological processes. They are an integral part of the cell's deluge mechanism that triggers its self-destruction when it starts malfunctioning or becomes harmful to the organism.

These enzymes characteristically cleave their substrates at aspartic acid residues and were initially elucidated because of their function in apoptosis. However, further research has unveiled their role in non-apoptotic processes such as cell differentiation, proliferation, and immune response. Their dysregulation can lead to diseases like cancer, neurodegenerative disorders, autoimmune diseases, and infectious diseases.

Caspase detection methods and principles

Understanding their role, physiological and pathological importance lends to the need for their detection, which further allows researchers to reveal the mechanism behind several biological processes and diseases. The detection of these cysteine proteases involves novel and sophisticated procedures, following unique methods and principles.

The detection methods for Caspase majorly depend upon the activation of these enzymes. Caspase activation is a crucial step in apoptosis, wherein inactive precursors, procaspases, are processed into active enzymes. The detection of active caspases, therefore, signals the onset of apoptosis. Such monitoring helps in the direct measurement of apoptosis and insights into this essential cellular process.

Various techniques are employed for Caspase detection. Fluorescence microscopy and flow cytometry, using cell-permeable fluorochrome inhibitors of caspases, are standard methods. These inhibitors are potent, selective, and irreversible, binding to the active caspases within the cell. This binding can then be detected using fluorescence microscopy or flow cytometry. Other techniques involve western blotting and colorimetric methods that rely on specific substrates that can be recognized by specific caspases.

Another notable method is the homogenous assay method, which hinges on the principle of fluorescence resonance energy transfer (FRET). In this procedure, a specific substrate coated with fluorescent molecules gets cleaved by active caspases, altering the FRET signal. This change is then detectable, allowing researchers to deduce the presence and activity of caspases.

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