Constitutively expressed catalytic proteasomal subunits are up-regulated during neuronal differentiation and required for axon initiation, elongation and maintenance.
Inhibition of the proteasome by lactacystin, a specific blocker of the catalytic beta-subunits, results in transient neurite outgrowth by neuronal cell lines. Vice versa, as demonstrated in this study, treatment of pheochromocytoma (PC12) cells with nerve growth factor (NGF) or other differentiating agents reduces proteasomal activity. This is accompanied by an increase in mRNA and protein levels of the catalytically active subunits beta1, beta2 and beta5, but not of their inducible counterparts, indicating changes in subunit composition of the proteasome during neuronal differentiation. In contrast to neuronal cell lines, however, pre-treatment of primary neurons with proteasome inhibitors completely prevents axon formation, and lower concentrations of lactacystin (0.5-5 microm) significantly reduce axonal elongation and branching in vitro. Furthermore, established axonal networks degenerate rapidly and long-term survival of peripheral neurons is impaired in the presence of proteasome inhibitors. Axonal pathology is reminiscent of the morphological changes observed in neurodegenerative disorders and supports a crucial role of the constitutive catalytic subunits in axon initiation, maintenance and regeneration.
Division of Neuroanatomy, Innsbruck Medical University, Innsbruck, Austria. lars.klimaschewski@i-med.ac.at
Lars
L
Klimaschewski
Barbara
B
Hausott
Shota
S
Ingorokva
Kristian
K
Pfaller
D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D020134:Catalytic Domain / Q000187:drug effects / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005725:Ganglia, Autonomic / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D017950:Ganglia, Sensory / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D020439:Growth Cones / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D009410:Nerve Degeneration / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology; D020932:Nerve Growth Factor / Q000378:metabolism / Q000494:pharmacology; D009415:Nerve Net / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D009420:Nervous System / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D016716:PC12 Cells; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D061988:Proteasome Inhibitors; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D061988:Proteasome Inhibitors; D012333:RNA, Messenger; C067713:lactacystin; D020932:Nerve Growth Factor; D046988:Proteasome Endopeptidase Complex; D000111:Acetylcysteine