The function of two Rho family GTPases is determined by distinct patterns of cell surface localization.
Rho family GTPases are critical regulators in determining and maintaining cell polarity. In Saccharomyces cerevisiae, Rho3 and Cdc42 play important but distinct roles in regulating polarized exocytosis and overall polarity. Cdc42 is highly polarized during bud emergence and is specifically required for exocytosis at this stage. In contrast, Rho3 appears to play an important role during the isotropic growth of larger buds. Using a novel monoclonal antibody against Rho3, we find that Rho3 localizes to the cell surface in a dispersed pattern which is clearly distinct from that of Cdc42. Using chimeric forms of these GTPases, we demonstrate that a small region at the N terminus is necessary and sufficient to confer Rho3 localization and function onto Cdc42. Analysis of this domain reveals two essential elements responsible for distinguishing function. First, palmitoylation of a cysteine residue by the Akr1 palmitoyltransferase is required both for the switch of function and the switch of localization properties of this domain. Second, two basic residues distal to the palmitoylation site are required for regulating binding affinity with the Exo70 and Sec3 effectors. This demonstrates the importance of localization and effector binding in determining how these GTPases evolved specific functions at distinct stages of polarized growth.
Wu
Hao
H
Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7090, USA.
Brennwald
Patrick
P
D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D005089:Exocytosis; D005800:Genes, Fungal; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D054730:Protein Interaction Domains and Motifs; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
C103132:EXO70 protein, S cerevisiae; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D000217:Acyltransferases; C403284:ERF2 protein, S cerevisiae; C074647:RHO3 protein, S cerevisiae; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; D020741:rho GTP-Binding Proteins
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