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.
- URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=15479639
Keywords: Animals ; Caenorhabditis elegans/cytology/*physiology ; Caenorhabditis elegans Proteins/genetics/*metabolism ; Cell Division/*physiology ; *Embryo ; Nonmammalian/cytology/physiology ; Enzyme Activation ; Epistasis ; Genetic ; GTP-Binding Protein alpha Subunits/metabolism ; Guanine Nucleotide Dissociation Inhibitors/genetics/metabolism ; Guanine Nucleotide Exchange Factors/genetics/metabolism ; Microtubules/metabolism ; Mitotic Spindle Apparatus/metabolism ; Nuclear Proteins/genetics/*metabolism ; Protein Binding ; RNA Interference ; Research Support ; Non-U.S. Gov't ; Research Support ; U.S. Gov't ; P.H.S. ; Stress ; Mechanical ; Two-Hybrid System Techniques
Swiss Institute for Experimental Cancer Research (ISREC), 1066 Epalinges/Lausanne, Switzerland.
Record created on 2006-08-24, modified on 2016-08-08