Functions of the novel RhoGAP proteins RGA-3 and RGA-4 in the germ line and in the early embryo of C. elegans.
We have identified two redundant GTPase activating proteins (GAPs) - RGA-3 and RGA-4 - that regulate Rho GTPase function at the plasma membrane in early Caenorhabditis elegans embryos. Knockdown of both RhoGAPs resulted in extensive membrane ruffling, furrowing and pronounced pseudo-cleavages. In addition, the non-muscle myosin NMY-2 and RHO-1 accumulated on the cortex at sites of ruffling. RGA-3 and RGA-4 are GAPs for RHO-1, but most probably not for CDC-42, because only RHO-1 was epistatic to the two GAPs, and the GAPs had no obvious influence on CDC-42 function. Furthermore, knockdown of either the RHO-1 effector, LET-502, or the exchange factor for RHO-1, ECT-2, alleviated the membrane-ruffling phenotype caused by simultaneous knockdown of both RGA-3 and RGA-4 [rga-3/4 (RNAi)]. GFP::PAR-6 and GFP::PAR-2 were localized at the anterior and posterior part of the early C. elegans embryo, respectively showing that rga-3/4 (RNAi) did not interfere with polarity establishment. Most importantly, upon simultaneous knockdown of RGA-3, RGA-4 and the third RhoGAP present in the early embryo, CYK-4, NMY-2 spread over the entire cortex and GFP::PAR-2 localization at the posterior cortex was greatly diminished. These results indicate that the functions of CYK-4 are temporally and spatially distinct from RGA-3 and RGA-4 (RGA-3/4). RGA-3/4 and CYK-4 also play different roles in controlling LET-502 activation in the germ line, because rga-3/4 (RNAi), but not cyk-4 (RNAi), aggravated the let-502(sb106) phenotype. We propose that RGA-3/4 and CYK-4 control with which effector molecules RHO-1 interacts at particular sites at the cortex in the zygote and in the germ line.
Schmutz
Cornelia
C
Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
Stevens
Julia
J
Spang
Anne
A
D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000166:cytology / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D021961:Cell Membrane Structures / Q000378:metabolism / Q000648:ultrastructure; D016764:Cell Polarity; D048749:Cytokinesis; D018076:DNA, Complementary / Q000235:genetics; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000502:physiology*; D005854:Germ Cells / Q000166:cytology / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D034622:RNA Interference
C513388:CYK-4 protein, C elegans; D029742:Caenorhabditis elegans Proteins; D018076:DNA, Complementary; D020690:GTPase-Activating Proteins; C480837:NMY-2 protein, C elegans; C524405:RGA-3 protein, C elegans; C524406:RGA-4 protein, C elegans; D018995:Myosin Heavy Chains