Phosphorylation controls autoinhibition of cytoplasmic linker protein-170

Area of Science:

• Cell Biology
• Molecular Biology
• Cytoskeleton Dynamics

Background:

• Cytoplasmic linker protein (CLIP)-170 is a key microtubule (MT) plus-end-tracking protein.
• CLIP-170 regulates MT dynamics and links MTs to intracellular structures.
• Previous work showed CLIP-170 autoinhibition via N- and C-terminal association, affecting MT and dynactin p150(Glued) binding.

Purpose of the Study:

• To investigate the role of phosphorylation in regulating CLIP-170 conformation and function.
• To identify specific phosphorylation sites on CLIP-170.
• To determine how phosphorylation affects CLIP-170 binding to MTs and p150(Glued).

Main Methods:

• Site-directed mutagenesis to create phosphorylation-deficient and phosphomimetic mutants.
• Phosphoproteomic analysis to map phosphorylation sites.
• Biochemical assays to assess binding affinities and conformational states.

Main Results:

• Phosphorylation enhances the affinity between CLIP-170's N- and C-terminal domains, promoting an autoinhibited conformation.
• Specific phosphorylation sites were identified in the third serine-rich region.
• A phosphorylation-deficient mutant adopted an "open" conformation with increased binding to MT ends and p150(Glued).
• A phosphomimetic mutant remained in a "folded back" conformation with reduced MT association and no p150(Glued) interaction.

Conclusions:

• Phosphorylation is a critical regulator of CLIP-170 conformation.
• Phosphorylation-induced conformational changes lead to CLIP-170 autoinhibition.
• This regulation modulates CLIP-170's interaction with microtubules and the dynactin complex.