RGS-7 completes a receptor-independent heterotrimeric G protein cycle to asymmetrically regulate mitotic spindle positioning in C. elegans.
Heterotrimeric G proteins promote microtubule forces that position mitotic spindles during asymmetric cell division in C. elegans embryos. While all previously studied G protein functions require activation by seven-transmembrane receptors, this function appears to be receptor independent. We found that mutating a regulator of G protein signaling, RGS-7, resulted in hyperasymmetric spindle movements due to decreased force on one spindle pole. RGS-7 is localized at the cell cortex, and its effects require two redundant Galphao-related G proteins and their nonreceptor activators RIC-8 and GPR-1/2. Using recombinant proteins, we found that RIC-8 stimulates GTP binding by Galphao and that the RGS domain of RGS-7 stimulates GTP hydrolysis by Galphao, demonstrating that Galphao passes through the GTP bound state during its activity cycle. While GTPase activators typically inactivate G proteins, RGS-7 instead appears to promote G protein function asymmetrically in the cell, perhaps acting as a G protein effector.
Hess
Heather A
HA
Department of Genetics, Yale University, New Haven, CT 06520, USA.
Röper
Jens-Christian
JC
Grill
Stephan W
SW
Koelle
Michael R
MR
D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology; D018385:Centrosome / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000502:physiology; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors; D006160:Guanosine Triphosphate / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D011485:Protein Binding; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; C475458:G protein regulator 1, C elegans; C475459:G protein regulator 2, C elegans; D044385:GTP-Binding Protein alpha Subunits; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D020710:RGS Proteins; C413418:RIC-8 protein, C elegans; D011993:Recombinant Fusion Proteins; C493264:rgs-7 protein, C elegans; D006160:Guanosine Triphosphate; D020962:Heterotrimeric GTP-Binding Proteins