RIC-8 is required for GPR-1/2-dependent Galpha function during asymmetric division of C. elegans embryos.
Heterotrimeric G proteins are crucial for asymmetric cell division, but the mechanisms of signal activation remain poorly understood. Here, we establish that the evolutionarily conserved protein RIC-8 is required for proper asymmetric division of one-cell stage C. elegans embryos. Spindle severing experiments demonstrate that RIC-8 is required for generation of substantial pulling forces on astral microtubules. RIC-8 physically interacts with GOA-1 and GPA-16, two Galpha subunits that act in a partially redundant manner in one-cell stage embryos. RIC-8 preferentially binds to GDP bound GOA-1 and is a guanine nucleotide exchange factor (GEF) for GOA-1. Our analysis suggests that RIC-8 acts before the GoLoco protein GPR-1/2 in the sequence of events leading to Galpha activation. Furthermore, coimmunoprecipitation and in vivo epistasis demonstrate that inactivation of the Gbeta subunit GPB-1 alleviates the need for RIC-8 in one-cell stage embryos. Our findings suggest a mechanism in which RIC-8 favors generation of Galpha free from Gbetagamma and enables GPR-1/2 to mediate asymmetric cell division.
Afshar
Katayoun
K
Swiss Institute for Experimental Cancer Research (ISREC), 1066 Epalinges/Lausanne, Switzerland.
Willard
Francis S
FS
Colombo
Kelly
K
Johnston
Christopher A
CA
McCudden
Christopher R
CR
Siderovski
David P
DP
Gönczy
Pierre
P
D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000502:physiology; D004789:Enzyme Activation; D004843:Epistasis, Genetic; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000235:genetics / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D034622:RNA Interference; D008941:Spindle Apparatus / Q000378:metabolism; D013314:Stress, Mechanical; D020798:Two-Hybrid System Techniques
D029742:Caenorhabditis elegans Proteins; C475458:G protein regulator 1, C elegans; C475459:G protein regulator 2, C elegans; D044385:GTP-Binding Protein alpha Subunits; D020730:Guanine Nucleotide Dissociation Inhibitors; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; C413418:RIC-8 protein, C elegans