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1.
Elife ; 62017 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-28304276

RESUMO

Scaffold proteins modulate signalling pathway activity spatially and temporally. In budding yeast, the scaffold Bem1 contributes to polarity axis establishment by regulating the GTPase Cdc42. Although different models have been proposed for Bem1 function, there is little direct evidence for an underlying mechanism. Here, we find that Bem1 directly augments the guanine exchange factor (GEF) activity of Cdc24. Bem1 also increases GEF phosphorylation by the p21-activated kinase (PAK), Cla4. Phosphorylation abrogates the scaffold-dependent stimulation of GEF activity, rendering Cdc24 insensitive to additional Bem1. Thus, Bem1 stimulates GEF activity in a reversible fashion, contributing to signalling flux through Cdc42. The contribution of Bem1 to GTPase dynamics was borne-out by in vivo imaging: active Cdc42 was enriched at the cell pole in hypophosphorylated cdc24 mutants, while hyperphosphorylated cdc24 mutants that were resistant to scaffold stimulation displayed a deficit in active Cdc42 at the pole. These findings illustrate the self-regulatory properties that scaffold proteins confer on signalling pathways.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Guanosina Trifosfato/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteína cdc42 de Saccharomyces cerevisiae de Ligação ao GTP/metabolismo , Canais de Cloreto/metabolismo , Microscopia Intravital , Microscopia , Saccharomyces cerevisiae/fisiologia , Transdução de Sinais
2.
Mol Biol Cell ; 26(13): 2519-34, 2015 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-25947137

RESUMO

The coupling of endocytosis and exocytosis underlies fundamental biological processes ranging from fertilization to neuronal activity and cellular polarity. However, the mechanisms governing the spatial organization of endocytosis and exocytosis require clarification. Using a quantitative imaging-based screen in budding yeast, we identified 89 mutants displaying defects in the localization of either one or both pathways. High-resolution single-vesicle tracking revealed that the endocytic and exocytic mutants she4∆ and bud6∆ alter post-Golgi vesicle dynamics in opposite ways. The endocytic and exocytic pathways display strong interdependence during polarity establishment while being more independent during polarity maintenance. Systems analysis identified the exocyst complex as a key network hub, rich in genetic interactions with endocytic and exocytic components. Exocyst mutants displayed altered endocytic and post-Golgi vesicle dynamics and interspersed endocytic and exocytic domains compared with control cells. These data are consistent with an important role for the exocyst in coordinating endocytosis and exocytosis.


Assuntos
Endocitose/fisiologia , Exocitose/fisiologia , Saccharomycetales/fisiologia , Polaridade Celular/fisiologia , Redes e Vias Metabólicas , Transporte Proteico , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomycetales/genética , Saccharomycetales/metabolismo
3.
Biochem Biophys Res Commun ; 433(1): 1-5, 2013 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-23454383

RESUMO

Polarized growth of the yeast Saccharomyces cerevisiae depends on different biological processes and requires several signaling pathways. Signaling is mediated through a set of proteins, which include Rho3p and Rho4p GTPases. Although these two proteins are involved in the control of distinct aspects of polarized growth in yeast, they have a common regulator: the Rgd1 RhoGAP protein. Here we demonstrate that Rgd1p is phosphorylated by the Aurora B like kinase Ipl1 and we observe that loss of Ipl1 function leads to a new Rgd1p distribution in a small part of the cell population.


Assuntos
Proteínas Ativadoras de GTPase/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Aurora Quinases , Citocinese , Proteínas Ativadoras de GTPase/química , Proteínas Ativadoras de GTPase/genética , Genes Fúngicos , Peptídeos e Proteínas de Sinalização Intracelular/antagonistas & inibidores , Peptídeos e Proteínas de Sinalização Intracelular/genética , Mutação , Fosforilação , Processamento de Proteína Pós-Traducional , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Proteínas Serina-Treonina Quinases/genética , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/crescimento & desenvolvimento , Proteínas de Saccharomyces cerevisiae/antagonistas & inibidores , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/genética , Transdução de Sinais
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