Inactivation of the SMN complex by oxidative stress.
The SMN complex is essential for the biogenesis of small nuclear ribonucleoproteins (snRNPs), the major constituents of the spliceosome. Deficiency in functional SMN protein causes spinal muscular atrophy, a common motor neuron degenerative disease of severity commensurate with SMN levels and, correspondingly, snRNP assembly decreases. We developed a high-throughput screen for snRNP assembly modifiers and discovered that reactive oxygen species (ROS) inhibit SMN-complex activity in a dose-dependent manner. ROS-generating compounds, e.g., the environmental toxins menadione and beta-lapachone (in vivo IC(50) = 0.45 muM) also cause intermolecular disulfide crosslinking of SMN. Both the oxidative inactivation and SMN crosslinking can be reversed by reductants. We identified two cysteines that form SMN-SMN disulfide crosslinks, defining specific contact points in oligomeric SMN. Thus, the SMN complex is a redox-sensitive assemblyosome and an ROS target, suggesting that it may play a role in oxidative stress pathophysiology, which is associated with many degenerative diseases.
Wan
Lili
L
Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6148, USA.
Ottinger
Elizabeth
E
Cho
Sungchan
S
Dreyfuss
Gideon
G
D000595:Amino Acid Sequence; D003432:Cross-Linking Reagents / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000737:chemistry / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009285:Naphthoquinones / Q000737:chemistry / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000494:pharmacology; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism; D055532:SMN Complex Proteins; D016415:Sequence Alignment; D054852:Small Molecule Libraries / Q000494:pharmacology
D003432:Cross-Linking Reagents; D017362:Cyclic AMP Response Element-Binding Protein; D004220:Disulfides; D009285:Naphthoquinones; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D017382:Reactive Oxygen Species; D017411:Ribonucleoproteins, Small Nuclear; D055532:SMN Complex Proteins; D054852:Small Molecule Libraries; C014638:beta-lapachone; D003545:Cysteine; D004229:Dithiothreitol