NPTN65 IS A NEW TARGET FOR THE TREATMENT OF TAUOPATHIES

Abstract

The NXNL2 gene encodes by alternative splicing for a trophic factor RdCVF2 that enhances the function and the survival of neurons involved in long term memory. Now the inventors demonstrated that the cell surface receptor for the trophic factor RdCVF2 is NPTN65. The set-up of methods that could be used to screen for small molecules, agonists of RdCVF2 signaling in the brain would be suitable for the development of a future metabolic and redox treatment of tauopathies and in particular Alzheimer's disease.

Claims

1. A method for screening a plurality of test substances for use as drugs for the treatment of a tauopathy comprising the steps consisting of (a) testing each of the plurality of test substances for its ability to activate the NPTN65 signaling pathway in a cell and (b) positively selecting the test substances capable of activating said NPTN65 signaling pathway.

2. The method of claim 1 wherein the tauopathy is selected from the group consisting of Alzheimer's disease, traumatic brain injury, frontotemporal dementia, including the subtype of frontotemporal dementia and Parkinsonism linked to chromosome 17 (FTDP-17), progressive supranuclear palsy, corticobas al degeneration, Picks disease, and agyrophilic grain disease.

3. The method of claim 1 wherein the tauopathy is Alzheimer's disease.

4. The method of claim 1, wherein the step of testing comprises measuring the binding of a test substance to NPTN65, or to cells or membranes bearing NPTN65, or a fusion protein thereof by means of a label directly or indirectly associated with the test substance.

5. The method of claim 1 comprising contacting cells expressing NPTN65 with a test substance, measuring an NPTN65 mediated cellular response and comparing the NPTN65 mediated cellular response to a standard cellular response.

6. The method of claim 5 wherein the standard cellular response is measured in the presence of RdCVF2 and wherein a similar or increased NPTN65 mediated cellular response compared to the standard cellular response indicates that the test substance activates the NPTN65 signaling pathway.

7. The method of claim 1 comprising a) providing a plurality of cells expressing NPTN65 on their surface; b) incubating said plurality of cells with a test substance; c) determining whether said test substance binds to and activates NPTN65; and d) selecting the test substance that binds to and activates NPTN65.

Description

FIGURES

[0023] FIG. 1: RdCVF2 interacts specifically with neuroplastin 65. A. Schematic representation of the single-pass transmembrane proteins NPTN65 and NPTN55 encoded by alternative splicing of the NPTN gene. Notice the presence of a third immunoglobulin domain in NPTN65. B. Schematic representation of the coding exons of the NXNL2 gene and the two proteins product made by alternative splicing. The intron retention and the in-frame stop codon produced an inactive thioredoxin-like protein, RdCVF2 with a truncated thioredoxin fold. C. Binding between the candidate cell-surface receptors, transiently transfected in COS-1 cells, and the candidate ligands expressed as fusion proteins with the alkaline phosphatase (AP).

Example

[0024] The deficit in long term potentiation of the Nxnl2−/− mouse at 2 months of age was corrected by systemic administration of the combination of RdCVF2 and RdCVF2L using recombinant AAV2/9 carrying a GFP reporter. This result supports the existence of a NXNL2-meditated metabolic and redox signaling in the brain, similar to that of NXNL1 in the retina. In order to validate the hypothesis, we performed a metabolomic analysis of hippocampal slides. We show that the Nxnl2 hippocampus is deficient in glycolysis; glucose-6-phosphate and fructose-16-biphosphate accumulate which is a sign of the reduction of the glycolytic flux. We then demonstrated that the cell surface receptor for the trophic factor RdCVF2 is NPTN65 (FIG. 1). Our results demonstrate that NXNL2 gene encodes by alternative splicing for a trophic factor RdCVF2 that enhances the function and the survival of neurons involved in long term memory through binding to its cell surface receptor, neuroplastin p65 (NPTN65), stimulating glucose uptake and aerobic glycolysis to provide carbohydrate intermediates to build new dendritic spines and/or provide cytoplasmic ATP to regulate the NMDA receptors via the Na/K-ATPase. The long isoform RdCVF2L is a glutaredoxin that interacts with TAU preventing its oxidation, oligomerization, phosphorylation, aggregation and propagation. The function of RdCVF2L is regulated by RdCVF2 and its effect on glucose uptake through the pentose phosphate pathway.

REFERENCES

[0025] Throughout this application, various references describe the state of the art to which this invention pertains. The disclosures of these references are hereby incorporated by reference into the present disclosure.