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RESEARCH PRODUCT

ALS-Related Mutant FUS Protein Is Mislocalized to Cytoplasm and Is Recruited into Stress Granules of Fibroblasts from Asymptomatic <b><i>FUS </i></b>P525L Mutation Carriers

Antonietta NotaroMargherita Lo BelloVincenzo La BellaRossella SpataroFrancesca Luisa ConfortiFrancesca Di Fini

subject

0301 basic medicineBiologymedicine.diseaseSubcellular localizationTARDBPMolecular biology03 medical and health sciencesCell nucleus030104 developmental biology0302 clinical medicineStress granulemedicine.anatomical_structureNeurologyC9orf72CytoplasmmedicineNeurology (clinical)Amyotrophic lateral sclerosis030217 neurology & neurosurgeryRNA-Binding Protein FUS

description

<b><i>Background:</i></b> Amyotrophic lateral sclerosis (ALS) shows a strong genetic basis, with <i>SOD1</i>, <i>FUS</i>, <i>TARDBP</i>, and <i>C9ORF72 </i>being the genes most frequently involved<i>. </i>This has allowed identification of asymptomatic mutation carriers, which may be of help in understanding the molecular changes preceding disease onset. <b><i>Objectives:</i></b> We studied the cellular expression of FUS protein and the effect of heat-shock- and dithiothreitol-induced stress in fibroblasts from <i>FUS</i> P525L mutation carriers, healthy controls, and patients with sporadic ALS. <b><i>Methods:</i></b> Western blots and immunocytochemistry were performed to study the subcellular localization of FUS protein. Control and stressed cells were double stained with FUS and the stress marker TIA-R. <b><i>Results:</i></b> Fibroblasts from healthy controls and sporadic ALS cases showed a prominent nuclear FUS expression. In the 2 <i>FUS</i> P525L mutation carriers, instead, most cells showed a protein localization in both nucleus and cytoplasm, or exclusively in the cytoplasm. Stress prompted the formation of cytoplasmic granules in all subjects and in sporadic ALS FUS mislocalization to the cytoplasm. Cytoplasmic FUS was recruited into stress granules, which showed a time-dependent decrease in all subjects. However, in the <i>FUS</i> P525L fibroblasts, the granules persisted longer, and they were more numerous than those detected in the cells from controls and sporadic ALS patients. <b><i>Conclusions:</i></b> We show that in fibroblasts of <i>FUS</i> P525L mutation carriers, FUS mislocalized to the cytoplasm where it redistributed into stress granules with likely a dose effect, i.e. a higher number of cells with granules, which persist longer, than in controls and ALS cases. These data represent an early molecular change occurring before ALS onset, suggesting a transient preaggregative state.

https://doi.org/10.1159/000480085