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Spatial regulation of the exocyst complex by Rho1 GTPase

Abstract

Spatial regulation of membrane traffic is fundamental to many biological processes, including epithelial cell polarization and neuronal synaptogenesis. The multiprotein exocyst complex is localized to sites of polarized exocytosis, and is required for vesicle targeting and docking at specific domains of the plasma membrane. One component of the complex, Sec3, is thought to be a spatial landmark for polarized exocytosis. We have searched for proteins that regulate the polarized localization of the exocyst in the budding yeast Saccharomyces cerevisiae. Here we report that certain rho1 mutant alleles specifically affect the localization of the exocyst proteins. Sec3 interacts directly with Rho1 in its GTP-bound form, and functional Rho1 is needed both to establish and to maintain the polarized localization of Sec3. Sec3 is not the only mediator of the effect of Rho1 on the exocyst, because some members of the complex are correctly targeted independently of the interaction between Rho1 and Sec3. These results reveal the action of parallel pathways for the polarized localization of the exocytic machinery, both of which are under the control of Rho1, a master regulator of cell polarity.

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Figure 1: A screen for mutants that affect the polarized localization of the exocyst protein in the budding yeast S. cerevisiae.
Figure 2: Comparison of the localization of Sec3, Sec4, actin and Myo2 in wild-type and various alleles of rho1 mutants.
Figure 3: Sec3–GFP is mislocalized in rho1-2 and rho1-5 mutant cells recovering from G0 arrest at 37 °C.
Figure 4: The interaction of Sec3 and Rho GTPase by the yeast two-hybrid assay.
Figure 5: In vitro binding between Sec3 and Rho1.
Figure 6: Different domains of Sec3 mediate its interaction with Rho1 and the exocyst proteins.
Figure 7: Localization of Sec3 with an N-terminal deletion (Sec3ΔN–GFP) in wild-type cells.
Figure 8: Localization and protein binding of Sec3ΔN–GFP as the sole copy in the cell.
Figure 9: Rho1 coordinates various cellular activities through different effectors for polarized cell growth in the budding yeast S. cerevisiae.

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Acknowledgements

We thank N. Robinson for sharing preliminary results; Y. Takai, Y. Ohya, M. Hall, M. Snyder and E. Cabib for providing us with reagents; and P. De Camilli, I. Mellman, L. Du, E. Grote and C. Carr for constructive discussions. W.G. was supported by Brown–Cox and NIH postdoctoral fellowships. This study was supported by a grant to P.N. from the NIH and in part to a grant to F. T. from the NIH.

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Correspondence to Peter Novick.

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Guo, W., Tamanoi, F. & Novick, P. Spatial regulation of the exocyst complex by Rho1 GTPase. Nat Cell Biol 3, 353–360 (2001). https://doi.org/10.1038/35070029

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