Caspase-6 latent state stability relies on helical propensity

Area of Science:

• Biochemistry
• Molecular Biology
• Neuroscience

Background:

• Caspase-6 is an apoptotic protease implicated in neurodegenerative conditions like Alzheimer's and Huntington's diseases.
• It uniquely forms a latent state where helices obstruct the active site, requiring conformational change for substrate binding.

Purpose of the Study:

• To investigate the structural determinants governing the formation and stability of the latent state in caspase-6.
• To understand the role of specific residues and conformational transitions in caspase-6 activation and function.

Main Methods:

• Site-directed mutagenesis to introduce or remove helix-breaking residues.
• Biophysical techniques to assess the structure and stability of different caspase-6 conformations.
• Enzyme kinetics to study substrate binding and activation.

Main Results:

• The absence of helix-breaking residues is critical for maintaining the extended helical conformation of the latent caspase-6 state.
• Introducing helix-breaking residues, similar to those in caspase-3 or -7, destabilizes the latent state.
• Caspase-6 appears to transition through a low-stability intermediate to bind active-site ligands.

Conclusions:

• Caspase-6's unique latent state is stabilized by the lack of helix-breaking residues.
• This structural feature is essential for its distinct mechanism of action compared to other caspases.
• Understanding these mechanisms could offer insights into therapeutic strategies for neurodegenerative diseases.