New function of Superoxide dismutase 1 in the nuclear compartment

Background: Recent evidences showed that, in PBMCs from sALS patients, there is an over-expression of SODJ mRNA (1). which in contrast with the uoehanged cytopla.•mic level of the protein [2). nus discrepancy could be explained considering' a re-Iocalization of Ute "nlissing" protein in the nucleus. Mnreovec, in PBMCs of sALS patienls. SOD 1 minslocates from the cytopl&sm to the nuclear com• partrncntin stressful conditions [3J. Objective.~: The exact role of SODJ in the nuclear oompanmenr remains a critical issue to clarify. Thus, we aim to investigate whether and how nuclear $001 COUid XCl ag.ainst oxidative SttCSS holh itl 1\eO• IOb!IUtolJla cell line SHSY5Y, a celluler model of nearodegeneratio», and in PBMCs of sALS patients. Materials and melh(>ds: SOD! tocatizauon in SHSYSY and in ,ALS patients was investic.itcd by both WB and immnDC>fluOtCSCcnce. By means Mass Spectrometry (MS) we searched for the modifications ttl!O\ving for SOD I transtocation snd by lmmunop:ecipitation (IP) we identify the binding protein involved in <Cgul:ition of SOD I local.12.o· rion. Finally, by Comet assay we studied ifnucleor SOOI could exert a pro<ectivc role towards DNA damage. Results: First, we confirmed that undcc oxidative stress SODl re· locates into the nucleus; SODl levels decreases .n..r 30 min of lmM H202 treatment, and rescues ot T60; probably as a consequence of new protein synthesis. MS data highlight that SOD! nuclear re-tccalt• zation l• prompted by pbospborylation or both serine and threonine nt T60. Morco•-cr, the kinase cn~ymc Chk2 seems 10 play• critical role in the regulation of SODl Iocalizatlon. Comet M$0Y reveated that SODl· NLS cells showed nc comets, indicating that. when SOD l is located info the nucleus. minor or none DNA frogmen.tat.ion occutred. Fb1ally, nn increase in histone H3 llCCtylation at both T'.lO and T60, suggested us a possible involvement of nuclear SOD! in gene transcription, Discussion and Conclusion: [o response to oxh.huh1e mess, we demonslf3ted that SOD! ro-looetes nt nuclear level, where it plays new funelio~. We reported an involvement of nuclear SODJ in ceder to provide resistance againsr oxidative DNA damage, 1111d a role in the regulation or J;cnc tnms<:rip\ion.