title: Skb5, an SH3 adaptor protein, regulates Pmk1 MAPK signaling by controlling the intracellular localization of the MAPKKK Mkh1.
abstract: The mitogen-activated protein kinase (MAPK) cascade is a highly conserved signaling module composed of MAPK kinase kinases (MAPKKKs), MAPK kinases (MAPKK) and MAPKs. The MAPKKK Mkh1 is an initiating kinase in Pmk1 MAPK signaling, which regulates cell integrity in fission yeast (Schizosaccharomyces pombe). Our genetic screen for regulators of Pmk1 signaling identified Shk1 kinase binding protein 5 (Skb5), an SH3-domain-containing adaptor protein. Here, we show that Skb5 serves as an inhibitor of Pmk1 MAPK signaling activation by downregulating Mkh1 localization to cell tips through its interaction with the SH3 domain. Consistent with this, the Mkh1(3PA) mutant protein, with impaired Skb5 binding, remained in the cell tips, even when Skb5 was overproduced. Intriguingly, Skb5 needs Mkh1 to localize to the growing ends as Mkh1 deletion and disruption of Mkh1 binding impairs Skb5 localization. Deletion of Pck2, an upstream activator of Mkh1, impaired the cell tip localization of Mkh1 and Skb5 as well as the Mkh1-Skb5 interaction. Interestingly, both Pck2 and Mkh1 localized to the cell tips at the G1/S phase, which coincided with Pmk1 MAPK activation. Taken together, Mkh1 localization to cell tips is important for transmitting upstream signaling to Pmk1, and Skb5 spatially regulates this process.
authors.affiliation: Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kindai University, 3-4-1 Kowakae, Higashiosaka City, Osaka 577-8502, Japan.
authors.forename: Yuki
authors.identifier: 0000-0002-8539-5149
authors.initials: Y
authors.lastname: Kanda
authors.affiliation: Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kindai University, 3-4-1 Kowakae, Higashiosaka City, Osaka 577-8502, Japan.
authors.forename: Ryosuke
authors.identifier: 0000-0002-7467-0096
authors.initials: R
authors.lastname: Satoh
authors.affiliation: Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kindai University, 3-4-1 Kowakae, Higashiosaka City, Osaka 577-8502, Japan.
authors.forename: Saki
authors.identifier: 0000-0001-8675-365X
authors.initials: S
authors.lastname: Matsumoto
authors.affiliation: Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kindai University, 3-4-1 Kowakae, Higashiosaka City, Osaka 577-8502, Japan.
authors.forename: Chisato
authors.identifier: 0000-0002-1437-7824
authors.initials: C
authors.lastname: Ikeda
authors.affiliation: Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kindai University, 3-4-1 Kowakae, Higashiosaka City, Osaka 577-8502, Japan.
authors.forename: Natsumi
authors.identifier: 0000-0003-3222-5741
authors.initials: N
authors.lastname: Inutsuka
authors.affiliation: Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kindai University, 3-4-1 Kowakae, Higashiosaka City, Osaka 577-8502, Japan.
authors.forename: Kanako
authors.identifier: 0000-0002-9366-6172
authors.initials: K
authors.lastname: Hagihara
authors.affiliation: Division of Pharmaceutical Education, Faculty of Pharmacy, Kindai University, 3-4-1 Kowakae, Higashiosaka City, Osaka 577-8502, Japan.
authors.forename: Sumio
authors.identifier: 0000-0002-5069-8262
authors.initials: S
authors.lastname: Matzno
authors.affiliation: Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kindai University, 3-4-1 Kowakae, Higashiosaka City, Osaka 577-8502, Japan.
authors.forename: Sho
authors.identifier: 0000-0002-9595-2076
authors.initials: S
authors.lastname: Tsujimoto
authors.affiliation: Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kindai University, 3-4-1 Kowakae, Higashiosaka City, Osaka 577-8502, Japan.
authors.forename: Ayako
authors.identifier: 0000-0002-1879-9493
authors.initials: A
authors.lastname: Kita
authors.affiliation: Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kindai University, 3-4-1 Kowakae, Higashiosaka City, Osaka 577-8502, Japan sugiurar@phar.kindai.ac.jp.
authors.forename: Reiko
authors.identifier: 0000-0001-6946-0935
authors.initials: R
authors.lastname: Sugiura
mesh_terms: D015536:Down-Regulation; D016193:G1 Phase; D017353:Gene Deletion; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D042541:Intracellular Space / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D021381:Protein Transport; D016196:S Phase; D012568:Schizosaccharomyces / Q000166:cytology / Q000201:enzymology*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D029702:Schizosaccharomyces pombe Proteins; C403123:Skb5 protein, S pombe; D020928:Mitogen-Activated Protein Kinases; C516338:Pmk1 protein, S pombe; D020930:MAP Kinase Kinase Kinases; C106762:Mkh1 protein, S pombe
keywords: MAPKK kinase; PKC; SH3 adaptor protein; Schizosaccharomyces pombe; Skb5