Gβγ mediates activation of Rho guanine nucleotide exchange factor ARHGEF17 that promotes metastatic lung cancer progression

Abstract

Metastatic lung cancer is a major cause of death worldwide. Dissemination of cancer cells can be facilitated by various agonists within the tumor microenvironment, including by lysophosphatidic acid (LPA). We postulate that Rho guanine nucleotide exchange factors (RhoGEFs), which integrate signaling cues driving cell migration, are critical effectors in metastatic cancer. Specifically, we addressed the hypothetical role of ARHGEF17, a RhoGEF, as a potential effector of Gβγ in metastatic lung cancer cells responding to LPA. Here, we show that ARHGEF17, originally identified as a tumor endothelial marker, is involved in tumor growth and metastatic dissemination of lung cancer cells in an immunocompetent murine model. Gene expression–based analysis of lung cancer datasets showed that increased levels of ARHGEF17 correlated with reduced survival of patients with advanced-stage tumors. Cellular assays also revealed that this RhoGEF participates in the invasive and migratory responses elicited by Gi protein–coupled LPA receptors via the Gβγ subunit complex. We demonstrate that this signaling heterodimer promoted ARHGEF17 recruitment to the cell periphery and actin fibers. Moreover, Gβγ allosterically activates ARHGEF17 by the removal of inhibitory intramolecular restrictions. Taken together, our results indicate that ARHGEF17 may be a valid potential target in the treatment of metastatic lung cancer.

Allosteric Activation of RhoA Complexed with p115-RhoGEF Deciphered by Conformational Dynamics

“…Such interactions were shown to control the activation and autoinhibition of Arf GTPases through GEF conformational changes that involve hinge motion . Similarly, Gβγ was recently shown to allosterically activate ARHGEF17 by the removal of the autoinhibitory restrictions . Allostery is also involved in K-Ras4B–SOS1 activation .…”

“…Allostery is also involved in K-Ras4B–SOS1 activation . Recently, RhoGEFs have been identified as therapeutic targets for metastatic cancers. , Knowledge of the allosteric interactions taking place during the activation of RhoA by p115-RhoGEF, as well as the differences in the conformational dynamics between the active and inactive complexes, can shed further light on the RhoA activation process and mechanism and can help in drug design.…”

“…71 Similarly, Gβγ was recently shown to allosterically activate ARHGEF17 by the removal of the autoinhibitory restrictions. 72 Allostery is also involved in K-Ras4B−SOS1 activation. 47 Recently, RhoGEFs have been identified as therapeutic targets for metastatic cancers.…”

A commercial ARHGEF17/TEM4 antibody cross-reacts with Nuclear Mitotic Apparatus protein 1 (NuMA)

“…In concordance with a function in regulating cytoskeletal dynamics, TEM4 is also implicated in the maintenance of cell-cell adhesion and junctions [4] and depletion of endogenous TEM4 by shRNAs impaired Madin-Darby canine kidney (MDCK) and HUVEC cell junctions, disrupted MDCK actin formation in 3D culture and resulted in disfunction of endothelial cells barriers [4]. In an immunocompetent mouse model, TEM4 was found to be involved in tumor growth and metastatic dissemination of lung cancer cells [5]. Most recently, the Mitocheck genome wide RNAi screening effort had identified TEM4 as an essential mitotic protein [6].…”

A Commercial ARHGEF17/TEM4 antibody cross-reacts with Nuclear Mitotic Apparatus protein 1 (NuMA)

“…Here, we evaluate the specificity of a commercial rabbit polyclonal anti-TEM4 antibody available from multiple providers and that is used in the literature in multiple applications 5 including Western blotting and immunocytochemistry (3)(4)(5)7,17). Our results reveal strong cross-reactivity of this antibody with the Nuclear Mitotic Apparatus Protein 1 (NuMA) in Western blotting, immunoprecipitation and immunocytochemistry, indicating major limitations of its utility in these approaches.…”