Regulation of Rho-GEF Rgf3 by the arrestin Art1 in fission yeast cytokinesis.
Bottom Line: Using an Rgf3 conditional mutant and mislocalization experiments, we found that Art1 and Rgf3 are interdependent for localization to the division site.As expected, active Rho1 levels at the division site are reduced in art1∆ and rgf3 mutant cells.Taken together, these data reveal that the arrestin family protein Art1 regulates the protein levels and localization of the Rho-GEF Rgf3, which in turn modulates active Rho1 levels during fission yeast cytokinesis.
Affiliation: Graduate Program of Molecular, Cellular, and Developmental Biology, The Ohio State University, Columbus, OH 43210 Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210.Show MeSH
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Mentions: Our previous study showed that the art1-s34 mutant can be rescued by overexpression of Rho-GEFs Rgf1, Rgf2, and Rgf3 or Rho1 GTPase (Wu et al., 2010), but the mechanism is unknown. Rgf1 and Rgf2 have localizations and/or deletion phenotypes different from those of Art1 (Figures 1 and 2; Mutoh et al., 2005; Garcia et al., 2006; Wu et al., 2010). Thus we focused on Rgf3. Rgf3 is a known GEF for Rho1 that activates the cell wall–synthesizing enzymes β-glucan synthases and other effectors (Arellano et al., 1997, 1999; Nakano et al., 1997; Tajadura et al., 2004; Mutoh et al., 2005). We hypothesized that Art1 functions in the same pathway as Rgf3 and Rho1 for cell wall synthesis and cell integrity. To test this hypothesis, we investigated whether art1∆ cells can be rescued by Rgf3 or Rho1 overexpression. Cell lysis of art1∆ cells decreased to ≤ 5% when Rho1 or Rgf3 was overexpressed (Figure 3, A–C). In addition, we found that art1∆ was synthetic lethal at 25°C with rgf3-s44, a point mutation in the GEF domain of Rgf3 (Wu et al., 2010). Thus Art1 indeed functions in the same or a related pathway as Rgf3 and Rho1. Rho1 localizes to both the division site and cell tips (Arellano et al., 1997; Mutoh et al., 2005), whereas Art1 and Rgf3 only concentrate at the division site (Figure 2); thus it is more likely that Art1 interacts with Rgf3.
Affiliation: Graduate Program of Molecular, Cellular, and Developmental Biology, The Ohio State University, Columbus, OH 43210 Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210.