Year-end Sale % OFF 
Abstract
G protein-gated inwardly rectifying potassium channel (GIRK) plays a crucial role in regulating heart rate and neuronal excitability. The gating of GIRK is regulated by the association and dissociation of G protein βγ subunits (Gβγ), which are released from pertussis toxin-sensitive G protein α subunit (Gα(i/o)) upon GPCR activation in vivo. Several lines of evidence indicate that Gα(i/o) also interacts directly with GIRK, playing functional roles in the signaling efficiency and the modulation of the channel activity. However, the underlying mechanism for GIRK regulation by Gα(i/o) remains to be elucidated. Here, we performed NMR analyses of the interaction between the cytoplasmic region of GIRK1 and Gα(i3) in the GTP-bound state. The NMR spectral changes of Gα upon the addition of GIRK as well as the transferred cross-saturation (TCS) results indicated their direct binding mode, where the K(d) value was estimated as ∼1 mm. The TCS experiments identified the direct binding sites on Gα and GIRK as the α2/α3 helices on the GTPase domain of Gα and the αA helix of GIRK. In addition, the TCS and paramagnetic relaxation enhancement results suggested that the helical domain of Gα transiently interacts with the αA helix of GIRK. Based on these results, we built a docking model of Gα and GIRK, suggesting the molecular basis for efficient GIRK deactivation by Gα(i/o).
Highlights
G␥ is known to activate GIRK, G␣i/o modulates GIRK gating
The overall intensity reductions are caused by the slowing of the overall tumbling motion upon binding to GIRKCP-L, the further intensity reductions and apparent chemical shift changes reflect the direct binding of GIRKCP-L to G␣i3
Because cross-saturation is a phenomenon depending on the intermolecular 1H-1H distances, the transferred cross-saturation (TCS) results from GIRKCP-L to G␣i3 (Fig. 2) and vice versa (Fig. 3) indicated that the ␣2/␣3 site of G␣i3 and the ␣A helix of GIRKCP-L directly interact with each other
Summary
G␥ is known to activate GIRK, G␣i/o modulates GIRK gating. Results: The ␣2/␣3 helices of G␣i3 in the GTP-bound state directly bind to the ␣A helix of GIRK. The TCS and paramagnetic relaxation enhancement results suggested that the helical domain of G␣ transiently interacts with the ␣A helix of GIRK Based on these results, we built a docking model of G␣ and GIRK, suggesting the molecular basis for efficient GIRK deactivation by G␣i/o. An electrophysiological study using a G␣i1/G␣q chimera, in which the helical domain was replaced, revealed that the helical domain of G␣ is responsible for the specific activation of the GIRK channel [25] It remains unclear how G␣i/o modulates the GIRK gating property, and the elucidation of the molecular recognition mode of G␣i/o and GIRK is required. We identified the binding sites on G␣ and GIRK, respectively, and examined the binding mode by paramagnetic relaxation enhancement (PRE) experiments Based on these results, we built a docking model of G␣ and the cytoplasmic region of GIRK, suggesting the molecular basis for the efficient deactivation of the channel by G␣i/o
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
