Kinetic Scaffolding Mediated by a Phospholipase C- and Gq Signaling Complex

Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA.
Science (Impact Factor: 33.61). 11/2010; 330(6006):974-980. DOI: 10.1126/science.1193438


Transmembrane signals initiated by a broad range of extracellular stimuli converge on nodes that regulate phospholipase C
(PLC)–dependent inositol lipid hydrolysis for signal propagation. We describe how heterotrimeric guanine nucleotide–binding
proteins (G proteins) activate PLC-βs and in turn are deactivated by these downstream effectors. The 2.7-angstrom structure
of PLC-β3 bound to activated Gαq reveals a conserved module found within PLC-βs and other effectors optimized for rapid engagement of activated G proteins.
The active site of PLC-β3 in the complex is occluded by an intramolecular plug that is likely removed upon G protein–dependent
anchoring and orientation of the lipase at membrane surfaces. A second domain of PLC-β3 subsequently accelerates guanosine
triphosphate hydrolysis by Gαq, causing the complex to dissociate and terminate signal propagation. Mutations within this domain dramatically delay signal
termination in vitro and in vivo. Consequently, this work suggests a dynamic catch-and-release mechanism used to sharpen spatiotemporal
signals mediated by diverse sensory inputs.

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Available from: Stephanie N Hicks, Mar 12, 2015
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    • "The differential ability of Gα16QL and GαzQL to interact with Fhit (Figure 2A) permits identification of Fhit-interacting regions on Gα16 through gain of function analyses. Since the effector interacting domain is likely to reside in the carboxyl half of the Gα subunit [36,37], we have selected chimeras composed of Gαz backbones with their C-terminal regions increasingly replaced by Gα16 sequences all the way up to the β2 domain (Figure 4A); mirror images of selected chimeras were also included. Among the various chimeras examined, constitutively active N188QL and N210QL (N-terminal 188 or 210 amino acids from Gαz, respectively) were more efficiently pulled down by the anti-Flag affinity gel than their corresponding wild-types; both chimeras were as effective as, if not better than, Gα16QL (Figure 4B). "
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    • "Some Gα subunit effectors also enhance GTPase activity; particularly, phospholipase-Cβ serves as a GAP for Gαq, and the Gα12/13 subfamily RGS-RhoGEF effectors possess a GTPase-accelerating domain (the rgRGS domain) with distant homology to RGS proteins.40, 43 An additional class of Gα regulators is the GoLoco motif protein family, members of which serve as guanine nucleotide dissociation inhibitors (GDIs) by binding directly to Gα·GDP and preventing nucleotide release.44 "
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    • "PLC-ε is regulated directly by small GTPases of the Ras and Rho families, as well as subunits of G proteins (Bunney et al., 2006; Harden et al., 2009; Harden and Sondek, 2006). Crystal structures of human PLC-b3 (enzyme core or full-length) in complex with Gaq were recently solved, revealing novel structural insights into the function of each domain involved in Gaq-induced activation of PLC-b3 (Lyon et al., 2013, Waldo et al., 2010). Structure and regulation of PLC by GPCRs and other means have been recently reviewed (Gresset et al., 2012; Kadamur and Ross, 2013). "

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