Trio’s Rho-specific GEF domain is the missing Gα_q effector in C. elegans

Abstract

The G␣ q pathway is essential for animal life and is a central pathway for driving locomotion, egg laying, and growth in Caenorhabditis elegans, where it exerts its effects through EGL-8 (phospholipase C␤ [PLC␤]) and at least one other effector. To find the missing effector, we performed forward genetic screens to suppress the slow growth and hyperactive behaviors of mutants with an overactive G␣ q pathway. Four suppressor mutations disrupted the Rho-specific guanine-nucleotide exchange factor (GEF) domain of UNC-73 (Trio). The mutations produce defects in neuronal function, but not neuronal development, that cause sluggish locomotion similar to animals lacking EGL-8 (PLC␤). Strains containing null mutations in both EGL-8 (PLC␤) and UNC-73 (Trio RhoGEF) have strong synthetic phenotypes that phenocopy the arrested growth and near-complete paralysis of G␣ q -null mutants. Using cell-based and biochemical assays, we show that activated C. elegans G␣ q synergizes with Trio RhoGEF to activate RhoA. Activated G␣ q and Trio RhoGEF appear to be part of a signaling complex, because they coimmunoprecipitate when expressed together in cells. Our results show that Trio's Rho-specific GEF domain is a major G␣ q effector that, together with PLC␤, mediates the G␣ q signaling that drives the locomotion, egg laying, and growth of the animal.[Keywords: G␣ q ; Trio; Rho; phospholipase C␤; C. elegans] Supplemental material is available at http://www.genesdev.org.

Systemic and cell intrinsic roles of Gqα signaling in the regulation of innate immunity, oxidative stress, and longevity in Caenorhabditis elegans

“…The C. elegans p38 MAPK module functions in the intestine for oxidative stress resistance (8) and immunity (28). In agreement with the reconstitution experiments, intestine-restricted knockdown of sek-1 by RNAi caused increased sensitivity to pathogens and arsenite (Table 1, rows [11][12][13][14][15][16][17][18][19][20]. Intestine-restricted egl-8 or egl-30 knockdown also resulted in increased sensitivity to pathogens and arsenite similar to egl-8 or egl-30 knockdown in the entire animal (Table 1, rows [11][12][13][14][15][16][17][18][19][20].…”

“…egl-30 or egl-8 mutants have decreased DAG and decreased neuronal secretion (17). In addition to EGL-8, EGL-30 also signals independently through UNC-73 (Trio RhoGEF) to activate Rho signaling and influence growth, locomotion, and egg laying (18). Reduced neuronal signaling mediated by EGL-30 through activation of EGL-8 influences adult life span in an IISdependent manner (19).…”

Reversal of Salt Preference Is Directed by the Insulin/PI3K and Gq/PKC Signaling inCaenorhabditis elegans

“…egl-30(pe914) is a presumptive gain-offunction mutation because it caused hyperactive locomotion and constitutive egg-laying phenotypes (data not shown), which are typical phenotypes of egl-30(gf) alleles (Schade et al 2005;Williams et al 2007). pe914 is a missense mutation in linker I, a well-conserved domain of G q a across phylogeny ( Figure 4A).…”

“…Although activation of EGL-30 and addition of a DAG analog promote salt attraction, it is unknown whether EGL-30 is required for the production of DAG in ASER. GPA-12/G 12/13 a , RHO-1Rho (Mcmullan et al 2006), and UNC-73 Rho GEF (Williams et al 2007) also stimulate production of DAG. In motor neurons, EGL-30 activates phospholipase C-b EGL-8 phospholipase C-b, which results in production of DAG (Lackner et al 1999).…”

An Organelle Gatekeeper Function forCaenorhabditis elegansUNC-16 (JIP3) at the Axon Initial Segment

“…The live animal assays have been described in detail in previous studies: locomotion assays (Miller et al 1999;Reynolds et al 2005) and population growth rate assays (Williams et al 2007). …”