TGF-beta 1 enhances neurite outgrowth via regulation of proteasome function and EFABP.
Malfunction of the ubiquitin-proteasome system has been implicated as a causal factor in the pathogenesis of aggregation-related disorders, e.g. Parkinson's disease. We show here that Transforming growth factor-beta 1 (TGF-beta), a multifunctional cytokine and trophic factor for dopaminergic (DAergic) neurons modulates proteasome function in primary midbrain neurons. TGF-beta differentially inhibited proteasomal subactivities with a most pronounced time-dependent inhibition of the peptidyl-glutamyl peptide hydrolyzing-like and chymotrypsin-like subactivity. Regulation of proteasomal activity could be specifically quantified in the DAergic subpopulation. Protein blot analysis revealed an accumulation of ubiquitinated proteins after TGF-beta treatment. The identity of these enriched proteins was further analyzed by 2D-gel electrophoresis and mass spectrometry. We found epidermal fatty acid binding protein (EFABP) to be strongly increased and ubiquitinated after TGF-beta treatment and confirmed this finding by co-immunoprecipitation. While application of TGF-beta increased neurite regeneration in a scratch lesion model, downregulation of EFABP by siRNA significantly decreased this effect. We thus postulate that a differential regulation of proteasomal function, as demonstrated for TGF-beta, can result in an enrichment of proteins, such as EFABP, that mediate physiological functions, such as neurite regeneration.
Knöferle
Johanna
J
Department of Neurology, University Medicine Göttingen, Germany.
Ramljak
Sanja
S
Koch
Jan C
JC
Tönges
Lars
L
Asif
Abdul R
AR
Michel
Uwe
U
Wouters
Fred S
FS
Heermann
Stephan
S
Krieglstein
Kerstin
K
Zerr
Inga
I
Bähr
Mathias
M
Lingor
Paul
P
D000818:Animals; D049108:Cell Enlargement; D002478:Cells, Cultured; D004298:Dopamine / Q000378:metabolism; D005136:Eye Proteins / Q000378:metabolism*; D050556:Fatty Acid-Binding Proteins / Q000378:metabolism*; D006868:Hydrolysis; D008636:Mesencephalon / Q000502:physiology; D009416:Nerve Regeneration / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D016501:Neurites / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D054875:Ubiquitination
D005136:Eye Proteins; C107356:Fabp5 protein, rat; D050556:Fatty Acid-Binding Proteins; D009419:Nerve Tissue Proteins; D053773:Transforming Growth Factor beta1; D046988:Proteasome Endopeptidase Complex; D004298:Dopamine