Mapping pathogenic mutations suggests an innovative structural model for the pendrin (SLC26A4) transmembrane domain

Area of Science:

• Biochemistry
• Genetics
• Structural Biology

Background:

• Human pendrin (SLC26A4) is a vital anion transporter in the inner ear, thyroid, and kidney.
• Mutations in the SLC26A4 gene cause Pendred Syndrome and non-syndromic hearing loss with enlarged vestibular aqueduct (ns-EVA).
• The lack of an experimental structure hinders genotype-phenotype correlation for SLC26A4 mutations.

Purpose of the Study:

• To develop a novel three-dimensional (3D) model of the human pendrin transmembrane domain.
• To predict the transporter's topology and identify functionally important regions.

Main Methods:

• Utilized the SLC26Dg transporter structure as a template for homology modeling.
• Generated a 14-transmembrane (TM) segment topology for human pendrin.
• Mapped 147 clinically validated pathological SLC26A4 mutations onto the 3D model.

Main Results:

• The proposed model features a 14 TM topology, including two previously unrecognized non-canonical transmembrane segments critical for pendrin function.
• Mutation analysis revealed that the majority of pathological mutations cluster in these two novel TM regions.
• This provides a structural basis for understanding the impact of mutations on pendrin activity.

Conclusions:

• The novel 3D pendrin model offers critical insights into its structure-function relationship.
• This structural understanding is essential for accurately correlating SLC26A4 genotypes with clinical phenotypes like hearing loss.
• The model serves as a valuable tool for future research into pendrin-related disorders.