A divergent substrate-binding loop within the pro-oncogenic protein anterior gradient-2 forms a docking site for...

Area of Science:

• Molecular Biology
• Cancer Research
• Protein Interactions

Background:

• Anterior Gradient-2 (AGR2) is implicated in various cellular processes, including metastasis.
• Despite its known functions, AGR2 lacks well-validated binding partners.
• Understanding AGR2 interactions is crucial for elucidating its role in disease.

Purpose of the Study:

• To identify and validate binding proteins for AGR2.
• To investigate the role of ATP binding in the AGR2-Reptin interaction.
• To map the interaction domains between AGR2 and Reptin.

Main Methods:

• Yeast two-hybrid system to screen for AGR2-interacting proteins.
• Co-immunoprecipitation to validate protein complex formation in human cell lysates.
• Site-directed mutagenesis of Reptin's ATP binding motifs (Walker A and Walker B).
• Analysis of protein oligomerization, thermostability, and binding affinity.
• Mapping of the AGR2 interaction domain using overlapping peptide libraries.

Main Results:

• Reptin was identified as an AGR2-interacting protein, forming a stable complex in human cells.
• Reptin is overexpressed in breast cancer tissues, suggesting a role in cancer progression.
• Mutations in Reptin's ATP binding motifs (K83A, D299N) altered Reptin oligomerization, stability, and AGR2 binding.
• The Reptin binding site on AGR2 was mapped to an octapeptide loop (amino acids 104-111), with mutations Y104 and F111 destabilizing the complex.
• ATP binding motifs in Reptin regulate the stability of the AGR2-Reptin complex.

Conclusions:

• Reptin is a validated binding partner for AGR2, with its ATP binding motifs playing a key regulatory role in complex stability.
• The AGR2-Reptin interaction is implicated in cancer growth, as Reptin is overexpressed in breast cancer.
• Identification of the AGR2 binding motif and ATP-regulated Reptin activity provides a basis for developing targeted therapeutics and assays.