Identification of Rho GEF and RhoA Activation by Pull-Down Assays

Inhibition of Rho GEFs attenuates pulmonary fibrosis through suppressing myofibroblast activation and reprogramming profibrotic macrophages

Idiopathic pulmonary fibrosis has a poor prognosis, with existing medications only partially alleviating symptoms, highlighting the urgent need for new therapeutic approaches. The dysregulations of Rho GTPases/ROCK are related with various diseases, including fibrosis. Nevertheless, the development of drugs for pulmonary fibrosis treatment has predominantly concentrated on ROCK inhibitors. Small GTPases have been historically recognized as "undruggable". Here, we explore a novel Rho GEFs inhibitor GL-V9, and find that GL-V9 alleviates bleomycin-induced pulmonary fibrosis in mice by inhibiting myofibroblast activation and reprogramming profibrotic macrophages. Distinct from the mechanisms of the first-line drug Nintedanib, GL-V9 binds to the DH/PH domain of Rho GEFs and block the activation of Rho GTPase signaling. This action subsequently suppresses myofibroblast activation by interfering with Rho GTPase-dependent cytoskeletal reorganization and the activity of MRTF and YAP, and inhibits M2 macrophage polarization by modulating RhoA/STAT3 activity. The discovery of new regulatory mechanisms of GL-V9 suggests that targeting Rho GEFs represents a potent strategy for pulmonary fibrosis treatment.

Rhoa/ROCK, mTOR and Secretome-Based Treatments for Ischemic Stroke: New Perspectives

Ischemic stroke triggers a complex cascade of cellular and molecular events leading to neuronal damage and tissue injury. This review explores the potential therapeutic avenues targeting cellular signaling pathways implicated in stroke pathophysiology. Specifically, it focuses on the articles that highlight the roles of RhoA/ROCK and mTOR signaling pathways in ischemic brain injury and their therapeutic implications. The RhoA/ROCK pathway modulates various cellular processes, including cytoskeletal dynamics and inflammation, while mTOR signaling regulates cell growth, proliferation, and autophagy. Preclinical studies have demonstrated the neuroprotective effects of targeting these pathways in stroke models, offering insights into potential treatment strategies. However, challenges such as off-target effects and the need for tissue-specific targeting remain. Furthermore, emerging evidence suggests the therapeutic potential of MSC secretome in stroke treatment, highlighting the importance of exploring alternative approaches. Future research directions include elucidating the precise mechanisms of action, optimizing treatment protocols, and translating preclinical findings into clinical practice for improved stroke outcomes.

A cell-based GEF assay reveals new substrates for DENN domains and a role for DENND2B in primary ciliogenesis

Primary cilia are sensory antennae crucial for cell and organism development, and defects in their biogenesis cause ciliopathies. Ciliogenesis involves membrane trafficking mediated by small guanosine triphosphatases (GTPases) including Rabs, molecular switches activated by guanine nucleotide exchange factors (GEFs). The largest family of Rab GEFs is the DENN domain-bearing proteins. Here, we screen all 60 Rabs against two major DENN domain families using a cellular GEF assay, uncovering 19 novel DENN/Rab pairs. The screen reveals Rab10 as a substrate for DENND2B, a protein previously implicated in cancer and severe mental retardation. Through activation of Rab10, DENND2B represses the formation of primary cilia. Through a second pathway, DENND2B functions as a GEF for RhoA to control the length of primary cilia. This work thus identifies an unexpected diversity in DENN domain-mediated activation of Rabs, a previously unidentified non-Rab substrate for a DENN domain, and a new regulatory protein in primary ciliogenesis.