Inclusion Formation and Toxicity of the ALS Protein RGNEF and Its Association with the Microtubule Network

• Published in: International journal of molecular sciences Vol. 21; no. 16; p. 5597
• Main Authors: Di Gregorio, Sonja E, Volkening, Kathryn, Strong, Michael J, Duennwald, Martin L
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 05.08.2020; MDPI
• Subjects: ALS; Amyotrophic lateral sclerosis; Amyotrophic Lateral Sclerosis - genetics; Amyotrophic Lateral Sclerosis - pathology; Animals; Cell lines; Cytoplasm; Disease; Family medical history; Gene Expression Regulation - genetics; Guanine; Guanine nucleotide exchange factor; Guanine Nucleotide Exchange Factors - genetics; Heterozygote; Humans; Inclusion bodies; Inclusions; Kinases; Mammals; Microscopy; microtubules; Microtubules - genetics; Mutation; Neurodegeneration; Neurons - metabolism; Neurons - pathology; Nucleotides; Oxidative stress; Pathogenesis; Protein Binding - genetics; protein misfolding; Proteins; RGNEF; Spinal cord; Toxicity; Ubiquitin; Ubiquitin - genetics; yeast model; Yeasts - genetics; ALS; neurodegeneration; microtubules; protein misfolding; yeast model; RGNEF
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms21165597

The Rho guanine nucleotide exchange factor (RGNEF) protein encoded by the gene has been implicated in the neurodegenerative disease amyotrophic lateral sclerosis (ALS). Biochemical and pathological studies have shown that RGNEF is a component of the hallmark neuronal cytoplasmic inclusions in ALS-affected neurons. Additionally, a heterozygous mutation in has been identified in a number of familial ALS (fALS) cases that may give rise to one of two truncated variants of the protein. Little is known about the normal biological function of RGNEF or how it contributes to ALS pathogenesis. To further explore RGNEF biology we have established and characterized a yeast model and characterized RGNEF expression in several mammalian cell lines. We demonstrate that RGNEF is toxic when overexpressed and forms inclusions. We also found that the fALS-associated mutation in gives rise to an inclusion-forming and toxic protein. Additionally, through unbiased screening using the split-ubiquitin system, we have identified RGNEF-interacting proteins, including two ALS-associated proteins. Functional characterization of other RGNEF interactors identified in our screen suggest that RGNEF functions as a microtubule regulator. Our findings indicate that RGNEF misfolding and toxicity may cause impairment of the microtubule network and contribute to ALS pathogenesis.