The Cdc42 effectors Ste20, Cla4, and Skm1 down-regulate the expression of genes involved in sterol uptake by a mitogen-activated protein kinase-independent pathway.
In Saccharomyces cerevisiae, the Rho-type GTPase Cdc42 regulates polarized growth through its effectors, including the p21-activated kinases (PAKs) Ste20, Cla4, and Skm1. Previously, we demonstrated that Ste20 interacts with several proteins involved in sterol synthesis that are crucial for cell polarization. Under anaerobic conditions, sterols cannot be synthesized and need to be imported into cells. Here, we show that Ste20, Cla4, and Skm1 form a complex with Sut1, a transcriptional regulator that promotes sterol uptake. All three PAKs can translocate into the nucleus and down-regulate the expression of genes involved in sterol uptake, including the Sut1 targets AUS1 and DAN1 by a novel mechanism. Consistently, deletion of either STE20, CLA4, or SKM1 results in an increased sterol influx and PAK overexpression inhibits sterol uptake. For Ste20, we demonstrate that the down-regulation of gene expression requires nuclear localization and kinase activity of Ste20. Furthermore, the Ste20-mediated control of expression of sterol uptake genes depends on SUT1 but is independent of a mitogen-activated protein kinase signaling cascade. Together, these observations suggest that PAKs translocate into the nucleus, where they modulate expression of sterol uptake genes via Sut1, thereby controlling sterol homeostasis.
Lin
Meng
M
Institute of Biochemistry, Christian Albrecht University, 24098 Kiel, Germany.
Unden
Heike
H
Jacquier
Nicolas
N
Schneiter
Roger
R
Just
Ursula
U
Höfken
Thomas
T
D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D015536:Down-Regulation; D015966:Gene Expression Regulation, Fungal; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases; D020935:MAP Kinase Signaling System / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013261:Sterols / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; C466994:AUS1 protein, S cerevisiae; C107098:DAN1 protein, S cerevisiae; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D019913:Nuclear Localization Signals; C466995:PDR11 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; C547000:SUT1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D013261:Sterols; D014157:Transcription Factors; C105722:SKM1 protein, S cerevisiae; C095212:CLA4 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae