Dataset Information

Polarity mediates asymmetric trafficking of the Gbeta heterotrimeric G-protein subunit GPB-1 in C. elegans embryos.

ABSTRACT: Asymmetric cell division is an evolutionarily conserved process that gives rise to daughter cells with different fates. In one-cell stage C. elegans embryos, this process is accompanied by asymmetric spindle positioning, which is regulated by anterior-posterior (A-P) polarity cues and driven by force generators located at the cell membrane. These force generators comprise two G? proteins, the coiled-coil protein LIN-5 and the GoLoco protein GPR-1/2. The distribution of GPR-1/2 at the cell membrane is asymmetric during mitosis, with more protein present on the posterior side, an asymmetry that is thought to be crucial for asymmetric spindle positioning. The mechanisms by which the distribution of components such as GPR-1/2 is regulated in time and space are incompletely understood. Here, we report that the distribution of the G? subunit GPB-1, a negative regulator of force generators, varies across the cell cycle, with levels at the cell membrane being lowest during mitosis. Furthermore, we uncover that GPB-1 trafficks through the endosomal network in a dynamin- and RAB-5-dependent manner, which is most apparent during mitosis. We find that GPB-1 trafficking is more pronounced on the anterior side and that this asymmetry is regulated by A-P polarity cues. In addition, we demonstrate that GPB-1 depletion results in the loss of GPR-1/2 asymmetry during mitosis. Overall, our results lead us to propose that modulation of G? trafficking plays a crucial role during the asymmetric division of one-cell stage C. elegans embryos.

SUBMITTER: Thyagarajan K

PROVIDER: S-EPMC3188591 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature

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Polarity mediates asymmetric trafficking of the Gbeta heterotrimeric G-protein subunit GPB-1 in C. elegans embryos.

Thyagarajan Kalyani K Afshar Katayoun K Gönczy Pierre P

Development (Cambridge, England) 20110701 13

Asymmetric cell division is an evolutionarily conserved process that gives rise to daughter cells with different fates. In one-cell stage C. elegans embryos, this process is accompanied by asymmetric spindle positioning, which is regulated by anterior-posterior (A-P) polarity cues and driven by force generators located at the cell membrane. These force generators comprise two Gα proteins, the coiled-coil protein LIN-5 and the GoLoco protein GPR-1/2. The distribution of GPR-1/2 at the cell membra ...[more]

PMID: 21652650

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Project description:Heterotrimeric GTP-binding proteins, which consist of Galpha, Gbeta, and Ggamma subunits, play important roles in transducing extracellular signals perceived by cell surface receptors into intracellular physiological responses. In addition to a single prototypical Galpha protein (GPA1), Arabidopsis has three unique Galpha-like proteins, known as XLG1, XLG2, and XLG3, that have been found to be localized in nuclei, although their functions and mode of action remain largely unknown. Through a transcriptomic analysis, we found that XLG2 and XLG3 were rapidly induced by infection with the bacterial pathogen Pseudomonas syringae, whereas the XLG1 transcript level was not affected by pathogen infection. A reverse genetic screen revealed that the xlg2 loss-of-function mutation causes enhanced susceptibility to P. syringae. Transcriptome profiling revealed that the xlg2 mutation affects pathogen-triggered induction of a small set of defense-related genes. However, xlg1 and xlg3 mutants showed no difference from wild-type plants in resistance to P. syringae. In addition, the xlg2 xlg3 double mutant and the xlg1 xlg2 xlg3 triple mutant were not significantly different from the xlg2 single mutant in the disease resistance phenotype, suggesting that the roles of XLG1 and XLG3 in defense, if any, are less significant than for XLG2. Constitutive overexpression of XLG2 leads to the accumulation of abnormal transcripts from multiple defense-related genes. Through co-immunoprecipitation assays, XLG2 was found to interact with AGB1, the sole Gbeta subunit in Arabidopsis, which has previously been found to be a positive regulator in resistance to necrotrophic fungal pathogens. However, no significant difference was found between three xlg single mutants, the xlg2 xlg3 double mutant, the xlg triple mutant, and wild-type plants in resistance to the necrotrophic fungal pathogens Botrytis cinerea or Alternaria brassicicola. These results suggest that XLG2 and AGB1 are components of a G-protein complex different from the prototypical heterotrimeric G-protein and may have distinct functions in modulating defense responses.

Dataset Information

Polarity mediates asymmetric trafficking of the Gbeta heterotrimeric G-protein subunit GPB-1 in C. elegans embryos.

Publications

Polarity mediates asymmetric trafficking of the Gbeta heterotrimeric G-protein subunit GPB-1 in C. elegans embryos.

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