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Lack of GTP-bound Rho1p in secretory vesicles of Saccharomyces cerevisiae.

Abe M, Qadota H, Hirata A, Ohya Y - J. Cell Biol. (2003)

Bottom Line: Rho1p, an essential Rho-type GTPase in Saccharomyces cerevisiae, activates its effectors in the GTP-bound form.Rom2p, the GDP/GTP exchange factor of Rho1p, is preferentially localized on the plasma membrane even when vesicular transport is blocked.Based on these results, we propose that Rho1p is kept inactive in intracellular secretory organelles, resulting in repression of the activity of the cell wall-synthesizing enzyme within cells.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, FSB-101, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan.

ABSTRACT
Rho1p, an essential Rho-type GTPase in Saccharomyces cerevisiae, activates its effectors in the GTP-bound form. Here, we show that Rho1p in secretory vesicles cannot activate 1,3-beta-glucan synthase, a cell wall synthesizing enzyme, during vesicular transport to the plasma membrane. Analyses with an antibody preferentially reacting with the GTP-bound form of Rho1p revealed that Rho1p remains in the inactive form in secretory vesicles. Rom2p, the GDP/GTP exchange factor of Rho1p, is preferentially localized on the plasma membrane even when vesicular transport is blocked. Overexpression of Rom2p results in delocalization of Rom2p and accumulation of 1,3-beta-glucan in secretory vesicles. Based on these results, we propose that Rho1p is kept inactive in intracellular secretory organelles, resulting in repression of the activity of the cell wall-synthesizing enzyme within cells.

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Localization of Rho1p and Fks1p/2p in cells shifted to 37°C. Cells were cultured in YPD at 25°C, shifted to 37°C and cultured for 2 h. Cultured cells were fixed with formaldehyde and then stained for immunofluorescence microscopy with the anti-Rho1p antibody (left) or the anti-Fks1p/2p antibody (right). Strains used were as follows: wild-type (YPH500), sec12, sec1, and sec1 end4.
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fig1: Localization of Rho1p and Fks1p/2p in cells shifted to 37°C. Cells were cultured in YPD at 25°C, shifted to 37°C and cultured for 2 h. Cultured cells were fixed with formaldehyde and then stained for immunofluorescence microscopy with the anti-Rho1p antibody (left) or the anti-Fks1p/2p antibody (right). Strains used were as follows: wild-type (YPH500), sec12, sec1, and sec1 end4.

Mentions: We analyzed the biosynthetic and transport processes of nascent GS after synthesis of the subunit proteins Rho1p and Fks1p/2p. To examine how Rho1p and Fks1p/2p are transported to the plasma membrane, we observed their localization when vesicular transport was blocked by sec mutations (Kaiser et al., 1997). Consistent with previous reports (Yamochi et al., 1994; Qadota et al., 1996; Ayscough et al., 1999), immunofluorescent microscopic observations revealed that Rho1p and Fks1p/2p were localized at the site of growth in wild-type cells incubated at 25°C or shifted to 37°C and incubated for 2 h (Fig. 1Figure 1.


Lack of GTP-bound Rho1p in secretory vesicles of Saccharomyces cerevisiae.

Abe M, Qadota H, Hirata A, Ohya Y - J. Cell Biol. (2003)

Localization of Rho1p and Fks1p/2p in cells shifted to 37°C. Cells were cultured in YPD at 25°C, shifted to 37°C and cultured for 2 h. Cultured cells were fixed with formaldehyde and then stained for immunofluorescence microscopy with the anti-Rho1p antibody (left) or the anti-Fks1p/2p antibody (right). Strains used were as follows: wild-type (YPH500), sec12, sec1, and sec1 end4.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172714&req=5

fig1: Localization of Rho1p and Fks1p/2p in cells shifted to 37°C. Cells were cultured in YPD at 25°C, shifted to 37°C and cultured for 2 h. Cultured cells were fixed with formaldehyde and then stained for immunofluorescence microscopy with the anti-Rho1p antibody (left) or the anti-Fks1p/2p antibody (right). Strains used were as follows: wild-type (YPH500), sec12, sec1, and sec1 end4.
Mentions: We analyzed the biosynthetic and transport processes of nascent GS after synthesis of the subunit proteins Rho1p and Fks1p/2p. To examine how Rho1p and Fks1p/2p are transported to the plasma membrane, we observed their localization when vesicular transport was blocked by sec mutations (Kaiser et al., 1997). Consistent with previous reports (Yamochi et al., 1994; Qadota et al., 1996; Ayscough et al., 1999), immunofluorescent microscopic observations revealed that Rho1p and Fks1p/2p were localized at the site of growth in wild-type cells incubated at 25°C or shifted to 37°C and incubated for 2 h (Fig. 1Figure 1.

Bottom Line: Rho1p, an essential Rho-type GTPase in Saccharomyces cerevisiae, activates its effectors in the GTP-bound form.Rom2p, the GDP/GTP exchange factor of Rho1p, is preferentially localized on the plasma membrane even when vesicular transport is blocked.Based on these results, we propose that Rho1p is kept inactive in intracellular secretory organelles, resulting in repression of the activity of the cell wall-synthesizing enzyme within cells.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, FSB-101, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan.

ABSTRACT
Rho1p, an essential Rho-type GTPase in Saccharomyces cerevisiae, activates its effectors in the GTP-bound form. Here, we show that Rho1p in secretory vesicles cannot activate 1,3-beta-glucan synthase, a cell wall synthesizing enzyme, during vesicular transport to the plasma membrane. Analyses with an antibody preferentially reacting with the GTP-bound form of Rho1p revealed that Rho1p remains in the inactive form in secretory vesicles. Rom2p, the GDP/GTP exchange factor of Rho1p, is preferentially localized on the plasma membrane even when vesicular transport is blocked. Overexpression of Rom2p results in delocalization of Rom2p and accumulation of 1,3-beta-glucan in secretory vesicles. Based on these results, we propose that Rho1p is kept inactive in intracellular secretory organelles, resulting in repression of the activity of the cell wall-synthesizing enzyme within cells.

Show MeSH
Related in: MedlinePlus