Proteasome inhibitors impair RANKL-induced NF-kappaB activity in osteoclast-like cells via disruption of p62, TRAF6, CYLD, and IkappaBalpha signaling cascades.
Proteasome inhibitors represent a promising therapy for the treatment of relapsed and/or refractory multiple myeloma, a disease that is concomitant with osteolysis and enhanced osteoclast formation. While blockade of the proteosome pathway has been recently shown to influence osteoclast formation and function, the precise molecular cascade underlying these effects is presently unclear. Here, we provide evidence that proteasome inhibitors directly impair osteoclast formation and function via the disruption of key RANK-mediated signaling cascades. Disruption of the proteosome pathway using selective inhibitors (MG-132, MG-115, and epoxomicin) resulted in the accumulation of p62 and CYLD, and altered the subcellular targeting and distribution of p62 and TRAF6 in osteoclast-like cells. Proteosome inhibition also blocked RANKL-induced NF-kappaB activation, IkappaBalpha degradation and nuclear translocation of p65. The disruption in RANK-signaling correlated dose-dependently with an impairment in osteoclastogenesis, with relative potency epoxomicin > MG-132 > MG-115 based on equimolar concentrations. In addition, these inhibitors were found to impact osteoclastic microtubule organization and attenuate bone resorption. Based on these data we propose that deregulation of key RANK-mediated signaling cascades (p62, TRAF6, CYLD, and IkappaBalpha) underscores proteasome-mediated inhibition of osteolytic bone conditions.
Molecular Orthopaedic Laboratory, Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Nedlands, Western Australia, Australia.
Estabelle
E
Ang
Nathan J
NJ
Pavlos
Sarah L
SL
Rea
Ming
M
Qi
Tracy
T
Chai
John P
JP
Walsh
Thomas
T
Ratajczak
Ming H
MH
Zheng
Jiake
J
Xu
D000199:Actins / Q000378:metabolism; D000818:Animals; D001862:Bone Resorption; D002460:Cell Line; D003545:Cysteine; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D000074749:Deubiquitinating Enzyme CYLD; D004921:Erythropoietin / Q000378:metabolism; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008870:Microtubules / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D050863:Synaptotagmin I / Q000235:genetics / Q000378:metabolism; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism*; D051758:Transcription Factor TFIIH; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D015853:Cysteine Proteinase Inhibitors; C490981:Gtf2h1 protein, mouse; D020672:I-kappa B Proteins; D007976:Leupeptins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D009842:Oligopeptides; D061988:Proteasome Inhibitors; D053245:RANK Ligand; D050863:Synaptotagmin I; D048029:TNF Receptor-Associated Factor 6; D014157:Transcription Factors; C089486:carbobenzoxy-leucyl-leucyl-norvalinal; D004921:Erythropoietin; D000072000:NF-KappaB Inhibitor alpha; D051758:Transcription Factor TFIIH; C511601:CYLD protein, mouse; D000074749:Deubiquitinating Enzyme CYLD; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D003545:Cysteine; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C078846:epoxomicin