Rho1p, a yeast protein at the interface between cell polarization and morphogenesis

Area of Science:

• * Molecular Biology
• * Cell Biology
• * Biochemistry

Background:

• * The yeast cell wall's primary structural component, beta(1-->3)-D-glucan, is synthesized by beta(1-->3)-D-glucan synthase.
• * This enzyme's activity is known to depend on a guanosine triphosphate (GTP) binding protein.

Purpose of the Study:

• * To identify the specific GTP binding protein required for beta(1-->3)-D-glucan synthase activity.
• * To elucidate the role of this protein in yeast cell wall synthesis, polarized growth, and morphogenesis.

Main Methods:

• * Genetic analysis of rho1 mutants to assess GTP stimulation of glucan synthase.
• * Biochemical purification and identification of proteins in rho1 strains.
• * Investigation of Rho1p's interaction with protein kinase C (PKC) and its downstream signaling pathways.

Main Results:

• * Rho1p was identified as the essential GTP binding protein for beta(1-->3)-D-glucan synthase.
• * Rho1p deficiency in mutants resulted in defective GTP stimulation of glucan synthase, which was restored by adding Rho1p.
• * Rho1p was found to regulate protein kinase C independently of its role in glucan synthesis, and it colocalizes with actin patches at bud emergence sites.

Conclusions:

• * Rho1p is a critical regulator of yeast cell wall biosynthesis and polarized growth.
• * Rho1p plays a dual role in regulating both cell wall synthesis and the protein kinase C signaling pathway.
• * The findings highlight Rho1p's importance in yeast morphogenesis and cell division.