The p21-activated protein kinase-related kinase Cla4 is a coincidence detector of signaling by Cdc42 and phosphatidylinositol 4-phosphate.
Signal transduction pathways that co-regulate a given biological process often are organized into networks by molecules that act as coincidence detectors. Phosphoinositides and the Rho-type GTPase Cdc42 regulate overlapping processes in all eukaryotic cells. However, the coincidence detectors that link these pathways into networks remain unknown. Here we show that the p21-activated protein kinase-related kinase Cla4 of yeast integrates signaling by Cdc42 and phosphatidylinositol 4-phosphate (PI4P). We found that the Cla4 pleckstrin homology (PH) domain binds in vitro to several phosphoinositide species. To determine which phosphoinositides regulate Cla4 in vivo, we analyzed phosphatidylinositol kinase mutants (stt4, mss4, and pik1). This indicated that the plasma membrane pool of PI4P, but not phosphatidylinositol 4,5-bisphosphate or the Golgi pool of PI4P, is required for localization of Cla4 to sites of polarized growth. A combination of the Cdc42-binding and PH domains of Cla4 was necessary and sufficient for localization to sites of polarized growth. Point mutations affecting either domain impaired the ability of Cla4 to regulate cell morphogenesis and the mitotic exit network (localization of Lte1). Therefore, Cla4 must retain the ability to bind both Cdc42 and phosphoinositides, the hallmark of a coincidence detector. PI4P may recruit Cla4 to the plasma membrane where Cdc42 activates its kinase activity and refines its localization to cortical sites of polarized growth. In mammalian cells, the myotonic dystrophy-related Cdc42-binding kinase possesses p21-binding and PH domains, suggesting that this kinase may be a coincidence detector of signaling by Cdc42 and phosphoinositides.
Wild
Angela C
AC
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Yu
Jong W
JW
Lemmon
Mark A
MA
Blumer
Kendall J
KJ
D000483:Alleles; D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D005838:Genotype; D049452:Green Fluorescent Proteins; D015151:Immunoblotting; D007700:Kinetics; D050356:Lipid Metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D008938:Mitosis; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D020349:Surface Plasmon Resonance; D013696:Temperature; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D054462:p21-Activated Kinases
D008164:Luminescent Proteins; D018129:Phosphatidylinositol Phosphates; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C037178:phosphatidylinositol 4-phosphate; D049452:Green Fluorescent Proteins; C095212:CLA4 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020764:cdc42 GTP-Binding Protein