Wnt5a protects motor neurons in amyotrophic lateral sclerosis by regulating the Wnt/Ca2+ signaling pathway.

OBJECTIVES: We aimed to detect the expression profile of downstream signaling molecules of non-canonical Wnt pathway in SOD1G93A transgenic mice (ALS mice) and SOD1G93A mutant motor neuron-like hybrid (NSC-34) cells. Characterizing the molecular mechanism of the Wnt5a-mediated non-canonical Wnt/Ca2+ signaling pathway in motor neuron (MN) degeneration may provide a feasible approach to effective treatment of amyotrophic lateral sclerosis (ALS). METHODS: The expressions of CaMKII-α, CaMKII-ß and TAK1 in the spinal cord of SOD1G93A ALS transgenic mice at different ages were determined using western blotting and immunofluorescence. The level of Ca2+ and cell apoptosis were assessed with flow cytometry and cell viability was evaluated using MTS assay. Cell proliferation was analyzed by the EdU cell proliferation assay. Neurite length was measured after treatment with retinoic acid. RESULTS: CaMKII-α, CaMKII-ß, and TAK1 were down-regulated in the spinal cord of ALS mice. Ca2+ level and CaMKII-α, CaMKII-ß, and TAK1 were down-regulated in SOD1G93A mutant NSC-34 cells. Expression of Ca2+, CaMKII-α, CaMKII-ß, and TAK1 were up-regulated in SOD1G93A mutant NSC-34 cells after Wnt5a overexpression and down-regulated after Wnt5a knockdown. Overexpression of Wnt5a promoted cell viability and proliferation but inhibited cell apoptosis. Contrastingly, Wnt5a knockdown inhibited cell viability and proliferation but promoted cell apoptosis. CaMKII inhibitor KN-93 and CaMKII activator oleic acid reversed changes in cell viability, proliferation, apoptosis, and neurite outgrowth induced by Wnt5a overexpression and knockdown. CONCLUSIONS: This study demonstrates that Wnt5a protects MNs in ALS by regulating cell viability, proliferation, apoptosis, and neurite growth through the Wnt/Ca2+ signaling pathway. Our data indicate that the non-canonical Wnt/Ca2+ signaling pathway regulated by Wnt5a is involved in MN degeneration in ALS.

The mechanism of the WNT5A and FZD4 receptor mediated WNT/ß-catenin pathway in the degeneration of ALS spinal cord motor neurons.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with unknown etiology, characterized by motor neuron degeneration, and there is no highly effective treatment. The canonical WNT/ß-catenin signaling pathway has a critical role in the physiological and pathophysiological processes of the central nervous system. In this study, we investigated the regulatory mechanism of the WNT/ß-catenin signaling pathway from the perspective of ligand-receptor binding and its relationship with the degeneration of ALS motor neurons. We used hSOD1-G93A mutant ALS transgenic mice and hSOD1-G93A mutant NSC34 cells combined with morphological and molecular biology techniques to determine the role of the WNT/ß-catenin pathway in ALS. Our findings demonstrated that WNT5A regulates the WNT/ß-catenin signaling pathway by binding to the FZD4 receptor in the pathogenesis of ALS and affects the proliferation and apoptosis of ALS motor neurons. Therefore, these findings may lead to the development of novel therapies to support the survival of ALS motor neurons.

Potential Roles of the WNT Signaling Pathway in Amyotrophic Lateral Sclerosis.

The WNT signaling pathway plays an important role in the physiological and pathophysiological processes of the central nervous system and the neurodegenerative disease amyotrophic lateral sclerosis (ALS). We reviewed the literature pertinent to WNT/ß-catenin signaling in ALS from cellular studies, animal models, and human clinical trials. WNT, WNT receptors, and other components of the WNT signaling pathway are expressed in both ALS patients and transgenic mice, and are involved in the pathogenesis of ALS. Studies have shown that abnormal activation of the WNT/ß-catenin signaling pathway is related to neuronal degeneration and glial cell proliferation. WNT/Ca2+ signaling is associated with the pro-inflammatory phenotype of microglia; data on the muscle skeletal receptor Tyr kinase receptor in superoxide dismutase-1-G93A mice indicate that gene therapy is necessary for successful treatment of ALS. The varying profiles of lipoprotein receptor-related protein 4 antibodies in different ethnic groups suggest that individual treatment and multifactorial personalized approaches may be necessary for effective ALS therapy. In conclusion, the WNT signaling pathway is important to the ALS disease process, making it a likely therapeutic target.