Structural basis for TNIP1 binding to FIP200 during mitophagy.

Area of Science:

• Cellular Biology
• Molecular Biology
• Biochemistry

Background:

• TNIP1 regulates mitophagy by disrupting the Unc-51-like kinase complex.
• Phosphorylation of TNIP1 by TBK1 enhances its interaction with FIP200.
• This interaction modulates autophagosome formation and expansion.

Purpose of the Study:

• To elucidate the molecular mechanism of FIP200's recognition of phosphorylated TNIP1.
• To understand how FIP200 distinguishes the phosphorylation status of the TNIP1 FIR motif.
• To provide structural insights into TNIP1-mediated mitophagy regulation.

Main Methods:

• X-ray crystallography to determine complex structures.
• Isothermal titration calorimetry (ITC) for binding affinity analysis.
• Molecular dynamics simulations and structural comparisons.

Main Results:

• Multiple crystal structures of FIP200 claw domain with phosphorylated TNIP1 FIR peptides were elucidated.
• Key residues in the FIP200 claw domain responsible for specific recognition were identified.
• TNIP1 Ser123 phosphorylation allows it to outcompete autophagy receptors for FIP200 binding.

Conclusions:

• Structural and biochemical analyses reveal the specific recognition of phosphorylated TNIP1 by the FIP200 claw domain.
• This interaction is crucial for TNIP1-dependent inhibition of mitophagy.
• Findings provide a foundation for understanding the detailed molecular mechanisms of mitophagy regulation.