p62 serves as a shuttling factor for TrkA interaction with the proteasome

Area of Science:

• Cell Biology
• Neuroscience
• Molecular Biology

Background:

• The scaffold protein p62 plays a role in the internalization and trafficking of TrkA receptors.
• TrkA receptors undergo deubiquitination by proteasomes before lysosomal degradation.

Purpose of the Study:

• To elucidate the role of p62 in the proteasomal degradation pathway of TrkA.
• To investigate how p62 mediates the interaction between ubiquitinated TrkA and the 26S proteasome.

Main Methods:

• Utilized p62 knockout (p62-/-) mouse brains to assess TrkA-Rpt1 interaction.
• Isolated proteasomes from p62-/- brains to study TrkA interaction.
• Performed in vitro binding assays using p62 domains (UBA, PB1/UbL) and Rpt1.
• Examined the effect of p62 reduction on neurotrophin-dependent TrkA turnover.

Main Results:

• In p62-/- mouse brains, TrkA failed to interact with Rpt1, a component of the 26S proteasome.
• TrkA interaction with Rpt1 was diminished in proteasomes from p62-/- brains but restored upon p62 addition.
• p62's UBA domain binds TrkA, while its PB1/UbL domain interacts with the Rpt1 AAA-ATPase cassette.
• Reduced p62 levels impaired neurotrophin-dependent TrkA turnover.

Conclusions:

• p62 functions as a shuttling factor, facilitating the interaction of ubiquitinated TrkA with the proteasome.
• p62 is critical for the efficient degradation of TrkA, impacting neuronal protein turnover and signaling.