Calpain and caspase: can you tell the difference?

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Neuronal death, both necrotic and apoptotic, is a hallmark of neurological and neurodegenerative disorders.
• Calpain and caspase 3 are cysteine proteases activated during neuronal death, with distinct activation patterns.
• Several cellular proteins are substrates for both calpain and caspase 3, suggesting overlapping roles.

Purpose of the Study:

• To investigate the roles of calpain and caspase 3 in neuronal death.
• To explore the susceptibility of cellular proteins to both proteases.
• To evaluate the therapeutic potential of protease inhibitors in neurodegenerative conditions.

Main Methods:

• Utilized neurotoxic challenges (hypoxia-hypoglycemia, excitotoxicity, metabolic inhibition) on cultured neurons.
• Administered calpain and caspase inhibitors to assess their effects on neuronal death.
• Analyzed the cleavage of specific protein substrates by calpains and caspases.

Main Results:

• Both calpain and caspase 3 were activated under various neurotoxic conditions.
• Proteins such as alpha/beta-fodrin, kinases, ADPRT/PARP, and tau were found to be cleaved by both proteases.
• Calpain inhibitors offered protection against necrotic and, to a lesser extent, apoptotic neuronal death.
• Caspase inhibitors significantly reduced apoptotic neuronal death.

Conclusions:

• Both calpain and caspase families play significant roles in neuronal structural and functional loss during degenerative processes.
• Targeting these proteases presents a potential therapeutic avenue for neurodegenerative diseases.
• Understanding the dual substrate specificity of these proteases is crucial for developing effective treatments.