Interleukin-11 binds specific EF-hand proteins via their conserved structural motifs

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Biology

Background:

• Interleukin-11 (IL-11) is a hematopoietic cytokine involved in diverse biological processes and cancer treatment.
• IL-11 possesses intrinsically disordered regions, suggesting potential for multiple target interactions.
• Previous research identified IL-11 interaction with calcium sensor protein S100P, dependent on calcium ions.

Purpose of the Study:

• To investigate the specificity of Interleukin-11 (IL-11) binding to various calcium-binding proteins.
• To identify specific calcium sensor proteins that interact with IL-11 in a calcium-dependent manner.
• To elucidate the structural basis for IL-11 interaction with EF-hand calcium-binding proteins.

Main Methods:

• Probing IL-11 specificity against a panel of calcium-binding proteins, including EF-hand calcium sensors (calmodulin, S100B, recoverin, NCS-1, GCAP-1/2), EF-hand calcium buffers (S100G, oncomodulin), and a non-EF-hand buffer (α-lactalbumin).
• Characterizing metal-dependent binding interactions and determining dissociation constants (Kd) using biophysical techniques.
• Analyzing conserved amino acid residues and structural motifs within EF-hand proteins potentially involved in IL-11 binding.
• Predicting secondary structure and hinge region accessibility of EF-hand proteins to understand binding specificity.

Main Results:

• A subset of calcium sensor proteins, including calmodulin, S100B, NCS-1, and GCAP-1/2, demonstrated metal-dependent binding to IL-11 with dissociation constants in the 1-19 μM range.
• Shared amino acid residues within conserved 'black' and 'gray' clusters of EF-hand proteins are implicated in IL-11 association.
• Alanine substitutions in S100P at specific residues significantly reduced IL-11 affinity, confirming their role in the interaction.
• Secondary structure and hinge region accessibility of EF-hand proteins are predicted to dictate the specificity and selectivity of IL-11 binding.

Conclusions:

• Interleukin-11 (IL-11) exhibits specific, calcium-dependent interactions with a subset of EF-hand calcium sensor proteins.
• Conserved structural motifs and hinge region characteristics of EF-hand proteins are critical determinants of IL-11 binding specificity.
• These interactions are likely relevant in pathological conditions involving cellular damage and extracellular component release.