Rho guanine nucleotide exchange factor (RGNEF) is a prosurvival factor under stress conditions

Cheung, Kevin; Droppelmann, Cristian A.; MacLellan, Adam; Cameron, I. R.; Withers, Benjamin; Campos-Melo, Danae; Volkening, Kathryn; Strong, Michael J.

doi:10.1016/j.mcn.2017.05.003

Cited by 12 publications

(15 citation statements)

References 31 publications

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“…By comparisons of Rgnef KO and GFP-Rgnef re-expressing ID8-IP cells, we show that Rgnef protects cells from increased ROS in anchorage-independent conditions. This role for Rgnef is consistent with previous findings in other models whereby Rgnef promotes cell survival after elevation of oxidative or other stress stimuli [36,37]. Although we find that a common set of antioxidant genes were regulated by Rgnef by comparisons of MOVCAR and ID8-IP knockout mouse models, the promoters of these genes also share common transcription factor binding sites for NRF2, KLF1, RELA (the 65 kDa subunit of NF-κB), and SOX2.…”

Section: Discussionsupporting

confidence: 91%

Rgnef promotes ovarian tumor progression and confers protection from oxidative stress

et al. 2019

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Ovarian cancer is the fifth-leading cause of cancer death among women. The dissemination of ovarian tumors and growth as spheroids accompanies late stage disease. In cell culture, ovarian tumor cell spheroids can exhibit elevated resistance to environmental stressors such as reactive oxygen species. Homeostatic balance of the antioxidant response is a protective mechanism that prevents anoikis, a form of programmed cell death. Signaling pathways activated by integrin receptors suppress anoikis. Rgnef (ARHGEF28/p190RhoGEF) is a guanine nucleotide exchange factor that is activated downstream of integrins. We find that Rgnef protein levels are elevated in late-stage serous ovarian cancer, high Rgnef mRNA levels are associated with decreased progression-free and overall survival, and genomic ARHGEF28 loss is associated with increased patient survival. Using transgenic and transplantable Rgnef knockout mouse models, we find that Rgnef is essential for supporting three-dimensional ovarian spheroid formation in vitro and tumor growth in mice. Using RNA-sequencing and bioinformatic analyses, we identify a conserved Rgnef-supported anti-oxidant gene signature including GPX4, Nqo1, and Gsta4; common targets of the NF-kB transcription factor. Antioxidant treatment enhanced growth of Rgnef-knockout spheroids and Rgnef re-expression facilitated NF-κB-dependent tumorsphere survival. These studies reveal a new role for Rgnef in ovarian cancer to facilitate NF-κB-mediated gene expression protecting cells from oxidative stress.

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Section: Discussionsupporting

confidence: 91%

Rgnef promotes ovarian tumor progression and confers protection from oxidative stress

et al. 2019

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“…3A). TDP-43 enriched micronuclei were also highly enriched in endogenous RGNEF despite the low levels of endogenous RGNEF in HEK293T cells 32 (Fig. 3B).…”

Section: Resultsmentioning

confidence: 92%

“…Previously, our group reported the existence of RGNEF-containing neuronal cytoplasmic inclusions (NCIs) in the motor neurons of ALS patients that co-aggregate with TDP-43 11,12 . RGNEF is a 190 kDa bifunctional guanine exchange factor/RNA binding protein that acts as a cellular survival factor under stress conditions 12,32 . RGNEF’s extensive localization in NCIs in ALS suggests it plays a critical role in the disease.…”

Section: Introductionmentioning

confidence: 99%

TDP-43 aggregation inside micronuclei reveals a potential mechanism for protein inclusion formation in ALS

Droppelmann

Campos-Melo

Moszczynski

et al. 2019

Sci Rep

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Amyotrophic lateral sclerosis (ALS) is a devastating progressive neurodegenerative disease with no known etiology. The formation of pathological protein inclusions, including RNA-binding proteins such as TDP-43 and rho guanine nucleotide exchange factor (RGNEF) are a hallmark of ALS. Despite intensive research, the mechanisms behind protein aggregate formation in ALS remains unclear. We have investigated the role of metabolic stress in protein aggregate formation analyzing how it is relevant to the co-aggregation observed between RGNEF and TDP-43 in motor neurons of ALS patients. Metabolic stress was able to induce formation of micronuclei, small nuclear fragments, in cultured cells. Notably, we observed the formation TDP-43 protein inclusions within micronuclei that co-aggregate with RGNEF and can be released to the cytoplasm. We observed that the leucine-rich domain of RGNEF is critical for its interaction with TDP-43 and localization in micronuclei. Finally, we described that micronuclei-like structures can be found in brain and spinal cord of ALS patients. This work is the first description of protein inclusion formation within micronuclei which also is linked with a neurodegenerative disease. The formation of TDP-43 inclusions within micronuclei induced by metabolic stress is a novel mechanism of protein aggregate formation which may have broad relevance for ALS and other neurodegenerative diseases.

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“…RGNEF is a multidomain protein with a combination of a GEF and RNA binding domain that is unique within the human proteome, together with many other functional domains, yet its basic biological function is just starting to be clarified [ 20 ]. It has been implicated in a number of diseases, including cancer and neurodegenerative diseases, particularly in ALS [ 16 , 17 , 19 , 23 , 24 , 26 , 40 , 41 , 42 ].…”

Section: Discussionmentioning

confidence: 99%

“…RGNEF belongs to the family of diffuse B-cell lymphoma (Dbl) GEFs and contains a leucine-rich region at its amino-terminus, a Plekstrin homology domain (PH), a cysteine-rich Zink-finger domain, FAK (focal adhesion kinase) binding domain, microtubule binding domain, and an nuclear localization signal (NLS, [ 18 ]. The normal cellular function of RGNEF is not well understood; however, it has been linked to multiple disorders in addition to ALS, including cancer, e.g., colorectal and ovarian cancer [ 19 , 20 , 21 , 22 , 23 ].…”

Section: Introductionmentioning

confidence: 99%

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

Gregorio

Volkening

Strong

et al. 2020

IJMS

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The Rho guanine nucleotide exchange factor (RGNEF) protein encoded by the ARHGEF28 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 ARHGEF28 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 ARGHEF28 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.

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Rho guanine nucleotide exchange factor (RGNEF) is a prosurvival factor under stress conditions

Cited by 12 publications

References 31 publications

Rgnef promotes ovarian tumor progression and confers protection from oxidative stress

Rgnef promotes ovarian tumor progression and confers protection from oxidative stress

TDP-43 aggregation inside micronuclei reveals a potential mechanism for protein inclusion formation in ALS

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

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