Synthetic calpain activator boosts neuronal excitability without extra Ca2+

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Calpain, a calcium-dependent protease, plays critical roles in cellular processes.
• Calpastatin inhibits calpain activity.
• Previous work demonstrated that calpastatin subdomains A and C activate m-calpain in vitro.

Purpose of the Study:

• To develop a membrane-permeable calpain activator.
• To investigate the effects of this activator on synaptic excitability in rat brain slices.
• To establish a tool for dissecting calpain system functions.

Main Methods:

• Conjugating an oligo-arginine tail to calpastatin subdomains A and C to create a membrane-permeable activator.
• Testing calpain activation and synaptic excitability in ex vivo rat hippocampal slices.
• Measuring basic excitability and long-term synaptic efficacy.

Main Results:

• The developed peptide conjugates effectively activated the calpain system.
• Treatment with the activator significantly increased basic excitability in hippocampal slices.
• Long-term synaptic efficacy was also significantly enhanced by the activator.
• The activator functions without apparent increases in cytoplasmic calcium.

Conclusions:

• The membrane-permeable calpain activator peptide conjugates are effective in modulating neuronal activity.
• This system can be utilized in various mammalian cells to probe calpain-dependent mechanisms.
• The tool offers a novel approach to study the calpain system's role in cellular functions, particularly in the nervous system.