RESUMO
The polarisome is a cortical proteinaceous microcompartment that organizes the growth of actin filaments and the fusion of secretory vesicles in yeasts and filamentous fungi. Polarisomes are compact, spotlike structures at the growing tips of their respective cells. The molecular forces that control the form and size of this microcompartment are not known. Here we identify a complex between the polarisome subunit Pea2 and the type V Myosin Myo2 that anchors Myo2 at the cortex of yeast cells. We discovered a point mutation in the cargo-binding domain of Myo2 that impairs the interaction with Pea2 and consequently the formation and focused localization of the polarisome. Cells carrying this mutation grow round instead of elongated buds. Further experiments and biophysical modeling suggest that the interactions between polarisome-bound Myo2 motors and dynamic actin filaments spatially focus the polarisome and sustain its compact shape.
Assuntos
Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/fisiologia , Polaridade Celular/genética , Polaridade Celular/fisiologia , Fungos/metabolismo , Fungos/fisiologia , Proteínas dos Microfilamentos/genética , Proteínas dos Microfilamentos/metabolismo , Mutação/genética , Cadeias Pesadas de Miosina/genética , Cadeias Pesadas de Miosina/metabolismo , Miosina Tipo V/genética , Miosina Tipo V/metabolismo , Ligação Proteica/fisiologia , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Vesículas Secretórias/metabolismo , Vesículas Secretórias/fisiologiaRESUMO
Once a cohort exceeds a certain size, it becomes mandatory to assign an identifier (ID) for each individual to ensure a secure, reliable, and unambiguous assignment. In the field of hematopoietic stem cell transplantation, with a still growing number of voluntary unrelated donors, it was recognized that a system needs to be developed to uniquely identify potential donors on a global scale to facilitate communication and to prevent errors in identification of donors. Efforts in this respect resulted in establishment of the GRID, with a defined structure and allocated rules. To successfully implement such a project, collaboration among all organizations involved in the process of volunteer donor recruitment, facilitation, and provision of hematopoietic stem cell products is necessary. Therefore, rapidly accessible information combined with a high level of communication and exchange of experiences is crucial. Established systems like the ISBT 128 and the Single European Code (SEC), which standardize the terminology, identification, coding, and labeling of tissues and cells of human origin, serve as a basis on how to successfully implement the GRID on a global scale.
RESUMO
The cortical endoplasmic reticulum (cER) of yeast underlies the plasma membrane (PM) at specific contact sites to enable a direct transfer of information and material between both organelles. During budding, directed movement of cER to the young bud followed by subsequent anchorage at its tip ensures the faithful inheritance of this organelle. The ER membrane protein Scs2p tethers the cER to the PM and to the bud tip through so far unknown receptors. We characterize Epo1p as a novel member of the polarisome that interacts with Scs2p exclusively at the cell tip during bud growth and show that Epo1p binds simultaneously to the Cdc42p guanosine triphosphatase-activating protein Bem3p. Deletion of EPO1 or deletion of BEM3 in a polarisome-deficient strain reduces the amount of cER at the tip. This analysis therefore identifies Epo1p as a novel and important component of the polarisome that promotes cER tethering at sites of polarized growth.
Assuntos
Proteínas de Transporte/metabolismo , Retículo Endoplasmático/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas de Transporte/genética , Polaridade Celular , Proteínas Ativadoras de GTPase/genética , Proteínas Ativadoras de GTPase/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Microscopia de Fluorescência , Microscopia de Vídeo , Complexos Multiproteicos , Mutação , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Mapeamento de Interação de Proteínas , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/crescimento & desenvolvimento , Proteínas de Saccharomyces cerevisiae/genética , Fatores de TempoRESUMO
We introduce a fluorescent reporter for monitoring protein-protein interactions in living cells. The method is based on the Split-Ubiquitin method and uses the ratio of two auto-fluorescent reporter proteins as signal for interaction (SPLIFF). The mating of two haploid yeast cells initiates the analysis and the interactions are followed online by two-channel time-lapse microscopy of the diploid cells during their first cell cycle. Using this approach we could with high spatio-temporal resolution visualize the differences between the interactions of the microtubule binding protein Stu2p with two of its binding partners, monitor the transient association of a Ran-GTPase with its receptors at the nuclear pore, and distinguish between protein interactions at the polar cortical domain at different phases of polar growth. These examples further demonstrate that protein-protein interactions identified from large-scale screens can be effectively followed up by high-resolution single-cell analysis.
