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RGS16 inhibits signalling through the G alpha 13-Rho axis
Eric N Johnson1, Tammy M Seasholtz, Abdul A Waheed
1Molecular Signal Transduction Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases/National Institute of Health, Rockville, MD 20852, USA.
Abstract:
G alpha 13 stimulates the guanine nucleotide exchange factors (GEFs) for Rho, such as p115Rho-GEF. Activated Rho induces numerous cellular responses, including actin polymerization, serum response element (SRE)-dependent gene transcription and transformation. p115Rho-GEF contains a Regulator of G protein Signalling domain (RGS box) that confers GTPase activating protein (GAP) activity towards G alpha 12 and G alpha 13 (ref. 3). In contrast, classical RGS proteins (such as RGS16 and RGS4) exhibit RGS domain-dependent GAP activity on G alpha i and G alpha q, but not G alpha 12 or G alpha 13 (ref 4). Here, we show that RGS16 inhibits G alpha 13-mediated, RhoA-dependent reversal of stellation and SRE activation. The RGS16 amino terminus binds G alpha 13 directly, resulting in translocation of G alpha 13 to detergent-resistant membranes (DRMs) and reduced p115Rho-GEF binding. RGS4 does not bind G alpha 13 or attenuate G alpha 13-dependent responses, and neither RGS16 nor RGS4 affects G alpha 12-mediated signalling. These results elucidate a new mechanism whereby a classical RGS protein regulates G alpha 13-mediated signal transduction independently of the RGS box.
Insights
Regulator of G protein Signaling (RGS) 16 protein inhibits G alpha 13 signaling pathways, impacting RhoA activity and cellular responses. This occurs through direct binding, independent of the RGS box, revealing a novel regulatory mechanism.
Area of Science:
- Cellular Biology
- Molecular Signaling
- G protein signaling pathways
Background:
- G alpha 13 protein activates Rho guanine nucleotide exchange factors (GEFs), like p115Rho-GEF.
- Activated Rho influences cellular processes including actin polymerization and gene transcription.
- Classical Regulator of G protein Signaling (RGS) proteins typically regulate G alpha i and G alpha q, not G alpha 12 or G alpha 13.
Purpose of the Study:
- To investigate the role of RGS16 in G alpha 13-mediated signaling.
- To elucidate the mechanism by which RGS16 regulates G alpha 13 activity.
- To determine if RGS proteins can modulate G alpha 13-dependent cellular responses.
Main Methods:
- Investigated the inhibitory effect of RGS16 on G alpha 13-mediated RhoA signaling.
- Examined the interaction between RGS16 and G alpha 13 using biochemical assays.
- Assessed the impact of RGS16 on the localization of G alpha 13 within the cell.
- Evaluated the effect of RGS16 and RGS4 on G alpha 13-dependent cellular responses like stellation and SRE activation.
Main Results:
- RGS16 inhibits G alpha 13-mediated RhoA-dependent reversal of stellation and SRE activation.
- The amino terminus of RGS16 directly binds to G alpha 13.
- This interaction causes G alpha 13 to translocate to detergent-resistant membranes (DRMs), reducing p115Rho-GEF binding.
- RGS4 does not interact with G alpha 13 or inhibit its signaling, and neither RGS16 nor RGS4 affects G alpha 12 signaling.
Conclusions:
- RGS16 regulates G alpha 13 signaling through a novel mechanism.
- This regulation occurs independently of the RGS box domain, involving direct binding and altered G alpha 13 localization.
- Classical RGS proteins can modulate G alpha 13 pathways, expanding their known functions.