Calcium interactions with Cx26 hemmichannel: Spatial association between MD simulations biding sites and variant...

Area of Science:

• Biophysics
• Molecular Biology
• Genetics

Background:

• Connexinopathies encompass diseases of connexin channels and hemichannels.
• Cx26 alterations are strongly linked to human deafness.
• Calcium ions play a critical role in regulating Cx26 hemichannel function.

Purpose of the Study:

• To investigate calcium ion distribution and binding sites within the Cx26 hemichannel using atomistic molecular dynamics simulations.
• To identify novel calcium binding sites and characterize their interactions with Cx26.
• To spatially correlate identified calcium binding sites with pathogenic variants in the CJB2 gene.

Main Methods:

• Extensive atomistic Molecular Dynamics (MD) simulations of the Cx26 hemichannel embedded in a lipid bilayer, reaching approximately 4 microseconds.
• Analysis of calcium distribution and localization using electron density profiles, density maps, and distance-time evolution.
• Spatial association of identified calcium binding sites with reported pathogenic variants in the CJB2 gene via ClinVar.

Main Results:

• Identification of several calcium binding sites, including previously suggested ones (GLU42, GLU47, GLY45, ASP50) and novel sites (ASP2, ASP117, ASP159, GLU114, GLU119, GLU120, VAL226).
• Detailed characterization of specific amino acid interactions with calcium and their stability.
• Spatial mapping of these calcium binding sites onto the 3D structure of Cx26 in relation to pathogenic variants.

Conclusions:

• This study provides the first detailed molecular insights into calcium binding within the Cx26 hemichannel.
• The identified novel calcium binding sites offer new targets for understanding Cx26 function and dysfunction.
• This work represents a foundational step towards linking molecular features of Cx26 to its associated pathological variants and diseases like deafness.