Myelin protein zero/P0 phosphorylation and function require an adaptor protein linking it to RACK1 and PKC alpha

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• Myelin protein zero (P0) is essential for peripheral nervous system myelination.
• Mutations in P0's cytoplasmic domain disrupt its function and cause inherited neuropathies like Charcot-Marie-Tooth disease (CMT).
• Protein kinase Calpha (PKCalpha)-mediated phosphorylation of P0 is implicated in myelination.

Purpose of the Study:

• To identify proteins interacting with P0's cytoplasmic tail.
• To elucidate the role of P0-interacting proteins in P0-mediated adhesion and phosphorylation.
• To understand the molecular mechanisms underlying P0 function in myelination and CMT.

Main Methods:

• Co-immunoprecipitation to identify P0-interacting proteins.
• Site-directed mutagenesis to study the effects of mutations on P0 binding and function.
• Analysis of P0 phosphorylation and adhesion in cells expressing wild-type and mutant P0.

Main Results:

• A 65-kD adaptor protein (p65) was identified, linking P0 to RACK1.
• p65 binding to P0 (residues 179-197) is necessary for P0 phosphorylation and adhesion.
• Mutations disrupting p65 binding or the PKCalpha substrate motif cause loss of P0 function and are linked to CMT.
• Restoring P0 phosphorylation via serine substitutions rescues adhesion defects.

Conclusions:

• The adaptor protein p65 plays a critical role in P0-mediated adhesion and phosphorylation by linking P0 to RACK1.
• PKCalpha-mediated phosphorylation of P0, facilitated by p65, is essential for proper myelination.
• Dysfunctional p65-P0 interaction is a novel mechanism contributing to inherited peripheral neuropathies like CMT.