Current Biology
Volume 8, Issue 22, 5 November 1998, Pages 1211-1214, S1-S2
Journal home page for Current Biology

Brief Communication
The Rho1 effector Pkc1, but not Bni1, mediates signalling from Tor2 to the actin cytoskeleton

https://doi.org/10.1016/S0960-9822(07)00511-8Get rights and content
Under an Elsevier user license
open archive

Abstract

In Saccharomyces cerevisiae, the phosphatidylinositol kinase homologue Tor2 controls the cell-cycle-dependent organisation of the actin cytoskeleton by activating the small GTPase Rho1 via the exchange factor Rom2 [1], [2]. Four Rho1 effectors are known, protein kinase C 1 (Pkc1), the formin-family protein Bni1, the glucan synthase Fks and the signalling protein Skn7 [2], [3]. Rho1 has been suggested to signal to the actin cytoskeleton via Bni1 and Pkc1; rho1 mutants have never been shown to have defects in actin organisation, however [2], [4]. We have further investigated the role of Rho1 in controlling actin organisation and have analysed which of the Rho1 effectors mediates Tor2 signalling to the actin cytoskeleton. We show that some, but not all, rho1 temperature-sensitive (rho1ts) mutants arrest growth with a disorganised actin cytoskeleton. Both the growth defect and the actin organisation defect of the rho1-2ts mutant were suppressed by upregulation of Pkc1 but not by upregulation of Bni1, Fks or Skn7. Overexpression of Pkc1, but not overexpression of Bni1, Fks or Skn7, also rescued a tor2ts mutant, and deletion of BNI1 or SKN7 did not prevent the suppression of the tor2ts mutation by overexpressed Rom2. Furthermore, overexpression of the Pkc1-controlled mitogen-activated protein (MAP) kinase Mpk1 suppressed the actin defect of tor2ts and rho1-2ts mutants. Thus, Tor2 signals to the actin cytoskeleton via Rho1, Pkc1 and the cell integrity MAP kinase cascade.

Cited by (0)

SB Helliwell, A Schmidt and MN Hall, Department of Biochemistry, Biozentrum, University of Basel, CH4056 Basel, Switzerland.

Y Ohya, Department of Biological Sciences, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan.

Present address for SB Helliwell: Department of Biology, MIT 68-553, Cambridge, Massachetts 02139-4307, USA.

E-mail address for MN Hall (corresponding author): [email protected].