A critical role of Gbetagamma in tumorigenesis and metastasis of breast cancer.

Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 02/2011; 286(15):13244-54. DOI: 10.1074/jbc.M110.206615
Source: PubMed

ABSTRACT A growing body of evidence indicates that G protein-coupled receptors (GPCRs) are involved in breast tumor progression and that targeting GPCRs may be a novel adjuvant strategy in cancer treatment. However, due to the redundant role of multiple GPCRs in tumor development, it may be necessary to target a common signaling component downstream of these receptors to achieve maximum efficacy. GPCRs transmit signals through heterotrimeric G proteins composed of Gα and Gβγ subunits. Here we evaluated the role of Gβγ in breast tumor growth and metastasis both in vitro and in vivo. Our data show that blocking Gβγ signaling with Gα(t) or small molecule inhibitors blocked serum-induced breast tumor cell proliferation as well as tumor cell migration induced by various GPCRs in vitro. Moreover, induced expression of Gα(t) in MDA-MB-231 cells inhibited primary tumor formation and retarded growth of existing breast tumors in nude mice. Blocking Gβγ signaling also dramatically reduced the incidence of spontaneous lung metastasis from primary tumors and decreased tumor formation in the experimental lung metastasis model. Additional studies indicate that Gβγ signaling may also play a role in the generation of a tumor microenvironment permissive for tumor progression, because the inhibition of Gβγ signaling attenuated leukocyte infiltration and angiogenesis in primary breast tumors. Taken together, our data demonstrate a critical role of Gβγ signaling in promoting breast tumor growth and metastasis and suggest that targeting Gβγ may represent a novel therapeutic approach for breast cancer.

Download full-text


Available from: Frederick E Domann, Aug 29, 2014
  • Source
    • "After G-protein–coupled receptor activation, the release of G could thus direct the assembly of a G–Rap1a– Radil signaling complex, leading to spatiotemporal activation of integrins. Especially relevant to our findings showing that the depletion of Radil inhibits the metastasis of MDA-MB-231 cells to lungs, activation of the CXCR4 receptor (Müller et al., 2001) and G subunits (Kirui et al., 2010; Tang et al., 2011) were previously shown to be required for this process. Additionally, given that loss of function for the ERM protein ezrin was recently demonstrated to be required for the Rap1- induced spreading to similar extent than Radil (Ross et al., 2011), studying the functional relationship between these proteins may reveal further clues about their mechanisms. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The small GTPase Rap1 regulates inside-out integrin activation and thereby influences cell adhesion, migration, and polarity. Several Rap1 effectors have been described to mediate the cellular effects of Rap1 in a context-dependent manner. Radil is emerging as an important Rap effector implicated in cell spreading and migration, but the molecular mechanisms underlying its functions are unclear. We report here that the kinesin KIF14 associates with the PDZ domain of Radil and negatively regulates Rap1-mediated inside-out integrin activation by tethering Radil on microtubules. The depletion of KIF14 led to increased cell spreading, altered focal adhesion dynamics, and inhibition of cell migration and invasion. We also show that Radil is important for breast cancer cell proliferation and for metastasis in mice. Our findings provide evidence that the concurrent up-regulation of Rap1 activity and increased KIF14 levels in several cancers is needed to reach optimal levels of Rap1-Radil signaling, integrin activation, and cell-matrix adhesiveness required for tumor progression.
    The Journal of Cell Biology 12/2012; 199(6). DOI:10.1083/jcb.201206051 · 9.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The Gβγ subunits of heterotrimeric G proteins transmit signals to control many cellular processes, including leukocyte migration. Gβγ signaling may regulate and be regulated by numerous signaling partners. Here, we reveal that WDR26, a member of the WD40 repeat protein family, directly bound free Gβγ in vitro, and formed a complex with endogenous Gβγ in Jurkat T cells stimulated by the chemokine SDF1α. Suppression of WDR26 by siRNAs selectively inhibited Gβγ-dependent phospholipase Cβ and PI3K activation, and attenuated chemotaxis in Jurkat T cells and differentiated HL60 cells in vitro and Jurkat T cell homing to lymphoid tissues in scid mice. Similarly, disruption of the WDR26/Gβγ interaction via expression of a WDR26 deletion mutant impaired Gβγ signaling and Jurkat T cell migration, indicating that the function of WDR26 depends on its binding to Gβγ. Additional data show that WDR26 also controlled RACK1, a negative regulator, in binding Gβγ and inhibiting leukocyte migration. Collectively, these experiments identify WDR26 as a novel Gβγ-binding protein that is required for the efficacy of Gβγ signaling and leukocyte migration.
    Journal of Biological Chemistry 11/2011; 286(51):43902-12. DOI:10.1074/jbc.M111.301382 · 4.57 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Previous studies indicate that ethanol can modulate glycine receptors (GlyR), in part, through Gβγ interaction with basic residues in the intracellular loop. In this study, we show that a seven amino acid peptide (RQH(C7)) having the primary structure of a motif in the large intracellular loop of GlyR (GlyR-IL) was able to inhibit the ethanol-elicited potentiation of this channel from 47 ± 2 to 16 ± 4%, without interfering with the effect of Gβγ on GIRK (G protein activated inwardly rectifying potassium channel) activation. RQH(C7) displayed a concentration-dependent effect on ethanol action in evoked and synaptic currents. A fragment of GlyR-IL without the basic amino acids did not interact with Gβγ nor inhibited ethanol potentiation of GlyR. In silico analysis using docking and molecular dynamics allowed to identify a region of approximately 350Å(2) involving aspartic acids 186, 228 and 246 in Gβγ where we propose that RQH(C7) binds and exerts its blocking action on the effect of ethanol in GlyR.
    Journal of Biological Chemistry 10/2012; DOI:10.1074/jbc.M112.393603 · 4.57 Impact Factor
Show more