14-3-3 protein binding blocks the dimerization interface of caspase-2

Area of Science:

• Molecular Biology
• Cellular Biology
• Structural Biology

Background:

• Caspase-2 (C2) is a crucial, evolutionarily conserved caspase initiating apoptosis.
• C2 activation involves dimerization and autoproteolytic cleavage.
• Phosphorylation at Ser139/164 and 14-3-3 binding inhibit C2 activation by maintaining procaspase-2 (proC2) in an immature state.

Purpose of the Study:

• To elucidate the structural mechanism of 14-3-3-mediated inhibition of C2 activation.
• To determine the molecular basis for 14-3-3 binding to proC2.

Main Methods:

• Structural characterization of the proC2 and 14-3-3 complex.
• Hydrogen/deuterium mass spectrometry.
• Protein crystallography (PDB IDs: 6SAD, 6S9K).

Main Results:

• 14-3-3 dimer binds proC2 through multiple regions, explaining isoform specificity and high affinity.
• Complex formation does not induce significant conformational changes in proC2.
• 14-3-3 masks proC2's nuclear localization sequence and p12 domain C-terminal region, transiently interacting with both domains.
• The masked p12 region is critical for C2 dimerization.

Conclusions:

• 14-3-3 inhibits proC2 activation by sterically hindering the dimerization interface.
• This provides a molecular understanding of 14-3-3's role in regulating C2-mediated apoptosis.