Trio's Rho-specific GEF domain is the missing Galpha q effector in C. elegans.
The Galpha(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 Cbeta [PLCbeta]) 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 Galpha(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 (PLCbeta). Strains containing null mutations in both EGL-8 (PLCbeta) and UNC-73 (Trio RhoGEF) have strong synthetic phenotypes that phenocopy the arrested growth and near-complete paralysis of Galpha(q)-null mutants. Using cell-based and biochemical assays, we show that activated C. elegans Galpha(q) synergizes with Trio RhoGEF to activate RhoA. Activated Galpha(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 Galpha(q) effector that, together with PLCbeta, mediates the Galpha(q) signaling that drives the locomotion, egg laying, and growth of the animal.
Williams
Stacey L
SL
Program in Molecular, Cell, and Developmental Biology, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA.
Lutz
Susanne
S
Charlie
Nicole K
NK
Vettel
Christiane
C
Ailion
Michael
M
Coco
Cassandra
C
Tesmer
John J G
JJ
Jorgensen
Erik M
EM
Wieland
Thomas
T
Miller
Kenneth G
KG
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D006801:Humans; D008954:Models, Biological; D009154:Mutation / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D054799:Phospholipase C beta / Q000235:genetics / Q000502:physiology; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D064067:Rho Guanine Nucleotide Exchange Factors; D015398:Signal Transduction / Q000235:genetics; D009435:Synaptic Transmission / Q000235:genetics; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D029742:Caenorhabditis elegans Proteins; C479565:Egl-30 protein, C elegans; D020662:Guanine Nucleotide Exchange Factors; D009419:Nerve Tissue Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; C111263:UNC-73 protein, C elegans; D017346:Protein Serine-Threonine Kinases; C099628:TRIO protein, human; D054799:Phospholipase C beta; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020742:rhoA GTP-Binding Protein; D000109:Acetylcholine