Dimerization of the CNNM extracellular domain

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Cystathionine-synthase (CBS)-pair domain divalent metal cation transport mediators (CNNMs) are essential magnesium transporters.
• CNNMs regulate magnesium homeostasis through direct Mg2+ transport and indirect modulation of TRPM7 channels.

Purpose of the Study:

• To determine the crystal structure of the extracellular domain of tapeworm CNNM4.
• To investigate the role of extracellular domain dimerization in CNNM function.

Main Methods:

• X-ray crystallography to determine the structure of tapeworm CNNM4 extracellular domain.
• Analytical ultracentrifugation to assess dimerization of human CNNM4 mutants.
• Cellular assays to evaluate Mg2+ transport activity of mouse CNNM2 mutants.

Main Results:

• The extracellular domain of tapeworm CNNM4 forms a dimer of immunoglobulin-like folds.
• Three glycosylation sites were identified on the extracellular domain.
• Mutations in the extracellular domain of human CNNM4 disrupted dimerization.
• An analogous mutation in mouse CNNM2 impaired its Mg2+ transport activity.

Conclusions:

• The extracellular domain of CNNMs plays a critical role in mediating dimerization.
• Dimerization is essential for the proper function of CNNMs in magnesium transport.
• Structural insights into CNNM4 provide a basis for understanding CNNM family function and potential therapeutic targets.