Disrupted zinc-binding sites in structures of pathogenic SOD1 variants D124V and H80R.

Mutations in human copper-zinc superoxide dismutase (SOD1) cause an inherited form of the fatal neurodegenerative disease amyotrophic lateral sclerosis (ALS). Here, we present structures of the pathogenic SOD1 variants D124V and H80R, both of which demonstrate compromised zinc-binding sites. The disruption of the zinc-binding sites in H80R SOD1 leads to conformational changes in loop elements, permitting non-native SOD1-SOD1 interactions that mediate the assembly of these proteins into higher-order filamentous arrays.

Down-regulation of a manganese transporter in the face of metal toxicity.

The yeast Smf1p Nramp manganese transporter is posttranslationally regulated by environmental manganese. Smf1p is stabilized at the cell surface with manganese starvation, but is largely degraded in the vacuole with physiological manganese through a mechanism involving the Rsp5p adaptor complex Bsd2p/Tre1p/Tre2p. We now describe an additional level of Smf1p regulation that occurs with toxicity from manganese, but not other essential metals.

Structural and biophysical properties of the pathogenic SOD1 variant H46R/H48Q.

Over 100 mutations in the gene encoding human copper-zinc superoxide dismutase (SOD1) cause an inherited form of the fatal neurodegenerative disease amyotrophic lateral sclerosis (ALS). Two pathogenic SOD1 mutations, His46Arg (H46R) and His48Gln (H48Q), affect residues that act as copper ligands in the wild type enzyme. Transgenic mice expressing a human SOD1 variant containing both mutations develop paralytic disease akin to ALS.

The effects of glutaredoxin and copper activation pathways on the disulfide and stability of Cu,Zn superoxide dismutase.

Mutations in Cu,Zn superoxide dismutase (SOD1) can cause amyotrophic lateral sclerosis (ALS) through mechanisms proposed to involve SOD1 misfolding, but the intracellular factors that modulate folding and stability of SOD1 are largely unknown. By using yeast and mammalian expression systems, we demonstrate here that SOD1 stability is governed by post-translational modification factors that target the SOD1 disulfide. Oxidation of the human SOD1 disulfide in vivo was found to involve both the copper chaperone for SOD1 (CCS) and the CCS-independent pathway for copper activation.

Mechanisms for activating Cu- and Zn-containing superoxide dismutase in the absence of the CCS Cu chaperone.

The Cu- and Zn-containing superoxide dismutase 1 (SOD1) largely obtains Cu in vivo by means of the action of the Cu chaperone CCS. Yet, in the case of mammalian SOD1, a secondary pathway of activation is apparent. Specifically, when human SOD1 is expressed in either yeast or mammalian cells that are null for CCS, the SOD1 enzyme retains a certain degree of activity.