TrkA receptor endolysosomal degradation is both ubiquitin and proteasome dependent

Traffic. 2008 Jul;9(7):1146-56. doi: 10.1111/j.1600-0854.2008.00751.x. Epub 2008 Apr 18.

Abstract

Gaps in our knowledge exist regarding the degradation of the tropomyosin-regulated kinase A (TrkA) receptor after addition of neurotrophin, nerve growth factor (NGF). TrkA is rapidly and transiently ubiquitinated upon addition of NGF. Here, we demonstrate that the polyubiquitin tag plays a definitive role in receptor sorting. Treatment of PC12 cells with lactacystin prevented NGF-dependent deubiquitination and degradation of TrkA. However, treatment with methylamine, bafilomycin or leupeptin, did not prevent NGF-dependent deubiquitination but blocked the degradation of TrkA. Employing co-immunoprecipitation, biochemical fractionation and confocal microscopy, the kinetics of receptor trafficking post-internalization was observed to occur as a sequel from endosome/multivesicular body, proteasomes, culminating with degradation in the lysosomes. The trafficking of the polyubiquitin-deficient TrkA receptor mutant K485R was impaired and likewise failed to degrade revealing that the receptor escapes degradation. The interaction of TrkA with proteasomes was confirmed by purification and co-immunoprecipitation. We provide evidence that proteasomal deubiquitinating enzymes trim K63-ubiquitin chains from the TrkA receptor prior to its delivery to lysosomes for degradation. Taken together, our results reveal the existence of a novel proteasome-dependent step in receptor degradation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Endosomes / metabolism*
  • Humans
  • Kinetics
  • Leupeptins / chemistry
  • Lysosomes / metabolism*
  • Macrolides / pharmacology
  • Methylamines / chemistry
  • Mutation
  • PC12 Cells
  • Proteasome Endopeptidase Complex / chemistry*
  • Rats
  • Receptor, trkA / metabolism*
  • Subcellular Fractions / metabolism
  • Ubiquitin / chemistry*

Substances

  • Leupeptins
  • Macrolides
  • Methylamines
  • Ubiquitin
  • bafilomycin A
  • methylamine
  • Receptor, trkA
  • Proteasome Endopeptidase Complex
  • leupeptin