title: Dynamic localization of LIN-5 and GPR-1/2 to cortical force generation domains during spindle positioning.
abstract: G protein signaling pathways regulate mitotic spindle positioning during cell division in many systems. In Caenorhabditis elegans embryos, G alpha subunits act with the positive regulators GPR-1/2 and LIN-5 to generate cortical pulling forces for posterior spindle displacement during the first asymmetric division. GPR-1/2 are asymmetrically localized at the posterior cortex by PAR polarity cues at this time. Here we show that LIN-5 colocalizes with GPR-1/2 in one-cell embryos during spindle displacement. Significantly, we also find that LIN-5 and GPR-1/2 are localized to the opposite, anterior cortex in a polarity-dependent manner during the nuclear centration and rotation movements that orient the forming spindle onto the polarity axis. The depletion of LIN-5 or GPR-1/2 results in decreased centration and rotation rates, indicating a role in force generation at this stage. The localization of LIN-5 and GPR-1/2 is largely interdependent and requires G alpha. Further, LIN-5 immunoprecipitates with G alpha in vivo, and this association is GPR-1/2 dependent. These results suggest that a complex of G alpha/GPR-1/2/LIN-5 is asymmetrically localized in response to polarity cues, and this may be the active signaling complex that transmits asymmetries to the force generation machinery during both nuclear rotation and spindle displacement.
authors.affiliation: Section of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA.
authors.forename: Dae Hwi
authors.initials: DH
authors.lastname: Park
authors.forename: Lesilee S
authors.initials: LS
authors.lastname: Rose
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism / Q000502:physiology*; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism / Q000502:physiology*; D002467:Cell Nucleus / Q000502:physiology; D016764:Cell Polarity; D004625:Embryo, Nonmammalian; D005260:Female; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D018715:Microscopy, Video; D011233:Precipitin Tests; D034622:RNA Interference; D012399:Rotation; D008941:Spindle Apparatus / Q000502:physiology*
chemical_list: D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; C475458:G protein regulator 1, C elegans; C475459:G protein regulator 2, C elegans; D044385:GTP-Binding Protein alpha Subunits; C404808:lin-5 protein, C elegans