Mutant products of the NF2 tumor suppressor gene are degraded by the ubiquitin-proteasome pathway.
Neurofibromatosis type 2 (NF2), a syndrome associated with multiple tumors of the nervous system, mostly schwannomas, is caused by mutations in the NF2 tumor suppressor gene that encodes schwannomin (Sch). Here we examined NF2 pathogenetic mutations that result in misfolding of the FERM domain. We found that these mutant forms of Sch were efficiently degraded by the ubiquitin-proteasome pathway. In transfected cells, Sch Delta F118 was 3-fold more efficiently degraded than the related molecule ezrin bearing the equivalent mutation. In heterozygous Nf2 knock-out mouse fibroblasts, endogenous mutant Sch Delta 81-121, but not wild type Sch, was also degraded by proteasomes. We further show that this degradation pathway is functional in primary Schwann cells. We analyzed Sch Delta 39-121 expressed in a transgenic mouse model of NF2 and found that Sch Delta 39-121, but not the endogenous wild type Sch, was unstable due to proteasome-mediated degradation. Altogether these results suggest that degradation of mutant Sch mediated by the ubiquitin-proteasome pathway is a physiopathological pathway contributing to the loss of Sch function in NF2 patients.
UMR144 CNRS/Institut Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France.
Alexis
A
Gautreau
Jan
J
Manent
Bruno
B
Fievet
Daniel
D
Louvard
Marco
M
Giovannini
Monique
M
Arpin
D000251:Adenosine Triphosphatases / Q000008:administration & dosage* / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D016515:Genes, Neurofibromatosis 2; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009097:Multienzyme Complexes / Q000378:metabolism*; D025581:Neurofibromin 2 / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011994:Recombinant Proteins / Q000378:metabolism; D012583:Schwann Cells / Q000378:metabolism; D017384:Sequence Deletion; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism*
D009097:Multienzyme Complexes; D025581:Neurofibromin 2; D011994:Recombinant Proteins; D025801:Ubiquitin; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases