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Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease inherited in a small subset of patients. The SOD1(G93A) transgenic mouse models this subset of patients, and studies of this strain have suggested that endoplasmic reticulum (ER) stress and deficits in ER chaperone function are contributors to ALS pathophysiology. Here, we demonstrate that the reticulon family of proteins is a novel regulator of the ER chaperone protein disulfide isomerase (PDI), and that through PDI, reticulon-4A (Nogo-A) can protect mice against the neurodegeneration that characterizes ALS. We show that overexpressing reticulon protein induces a punctate redistribution of PDI intracellularly, both in vitro and in vivo. Conversely, reduction of endogenous NogoA expression causes a more homogeneous expression pattern in vivo. These effects occur without induction of the unfolded protein response. To examine the effect of PDI redistribution on ALS disease progression, we conducted survival and behavior studies of SOD1(G93A) mice. Deletion of a single copy of the NogoA,B gene accelerates disease onset and progression, while deletion of both copies further worsens disease. We conclude that NogoA contributes to the proper function of the ER resident chaperone PDI, and is protective against ALS-like neurodegeneration. Our results provide a novel intracellular role for reticulon proteins and support the hypothesis that modulation of PDI function is a potential therapeutic approach to ALS.

The production and aggregation of cerebral amyloid-beta (Abeta) peptide are thought to play a causal role in Alzheimer's disease (AD). Previously, we found that the Nogo-66 receptor (NgR) interacts physically with both Abeta and the amyloid precursor protein (APP). The inverse correlation of Abeta levels with NgR levels within the brain may reflect regulation of Abeta production and/or Abeta clearance. Here, we assess the potential therapeutic benefit of peripheral NgR-mediated Abeta clearance in APPswe/PSEN-1deltaE9 transgenic mice. Through site-directed mutagenesis, we demonstrate that the central 15-28 aa of Abeta associate with specific surface-accessible patches on the leucine-rich repeat concave side of the solenoid structure of NgR. In transgenic mice, subcutaneous NgR(310)ecto-Fc treatment reduces brain Abeta plaque load while increasing the relative levels of serum Abeta. These changes in Abeta are correlated with improved spatial memory in the radial arm water maze. The benefits of peripheral NgR administration are evident when therapy is initiated after disease onset. Thus, the peripheral association of NgR(310)ecto-Fc with central Abeta residues provides an effective therapeutic approach for AD.