Competitive Microtubule Binding of PEX14 Coordinates Peroxisomal Protein Import and Motility

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Human PEX14 is crucial for peroxisomal protein import and anchors peroxisomes to microtubules (MT), influencing peroxisome motility.
• The N-terminal domain of PEX14 (PEX14-NTD) binds ligands during protein import, while also interacting with microtubules.

Purpose of the Study:

• To investigate the interaction between PEX14 and microtubules at a molecular level.
• To determine if PEX5 influences the binding of PEX14 to microtubules.

Main Methods:

• In vitro binding assays to measure the dissociation constant of PEX14-NTD to microtubular filaments.
• Identification of specific binding motifs of PEX14 on human ß-tubulin.
• Simultaneous binding experiments with PEX14, kinesin, and microtubules.
• Competition assays involving PEX5, PEX14, and tubulin.

Main Results:

• PEX14-NTD binds to microtubular filaments with a nanomolar dissociation constant.
• PEX14 interacts with two distinct motifs within the C-terminal region of human ß-tubulin.
• PEX14 and kinesin can bind to microtubules concurrently, with PEX14 binding sites near kinesin binding sites.
• PEX5 binding to PEX14 prevents PEX14 from binding to tubulin.

Conclusions:

• PEX5 competes with microtubules for PEX14 binding, potentially regulating peroxisome anchoring.
• This competition suggests a mechanism where peroxisome matrix protein import and motility are coordinated.
• The findings may explain how peroxisomes achieve homogeneous dispersion within mammalian cells.