title: Recruitment and activation of SLK at the leading edge of migrating cells requires Src family kinase activity and the LIM-only protein 4.
abstract: The Ste20-like kinase SLK plays a pivotal role in cell migration and focal adhesion turnover and is regulated by the LIM domain-binding proteins Ldb1 and Ldb2. These adapter proteins have been demonstrated to interact with LMO4 in the organization of transcriptional complexes. Therefore, we have assessed the ability of LMO4 to also interact and regulate SLK activity. Our data show that LMO4 can directly bind to SLK and activate its kinase activity in vitro and in vivo. LMO4 can be co-precipitated with SLK following the induction of cell migration by scratch wounding and Cre-mediated deletion of LMO4 in conditional LMO4(fl/fl) fibroblasts inhibits cell migration and SLK activation. Deletion of LMO4 impairs Ldb1 and SLK recruitment to the leading edge of migrating cells. Supporting this, Src/Yes/Fyn-deficient cells (SYF) expressing very low levels of LMO4 do not recruit SLK to the leading edge. Re-expression of wildtype Myc-LMO4 in SYF cells, but not a mutant version, restores SLK localization and kinase activity. Overall, our data suggest that activation of SLK by haptotactic signals requires its recruitment to the leading edge by LMO4 in a Src-dependent manner. Furthermore, this establishes a novel cytosolic role for the transcriptional co-activator LMO4.
authors.affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Kyla D
authors.initials: KD
authors.lastname: Baron
authors.affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Khalid
authors.initials: K
authors.lastname: Al-Zahrani
authors.affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Jillian
authors.initials: J
authors.lastname: Conway
authors.affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Cédrik
authors.initials: C
authors.lastname: Labrèche
authors.affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Storbeck
authors.affiliation: Walter and Eliza Hall Institute Biotechnology Centre, Bundoora, Victoria 3086, Australia.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Visvader
authors.affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Ottawa Hospital Research Institute, Cancer Therapeutics, Ottawa, Ontario, Canada. Electronic address: lsabourin@ohri.ca.
authors.forename: Luc A
authors.initials: LA
authors.lastname: Sabourin
mesh_terms: D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002465:Cell Movement; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D005347:Fibroblasts / Q000166:cytology* / Q000201:enzymology*; D017353:Gene Deletion; D057809:HEK293 Cells; D006801:Humans; D060588:LIM Domain Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011554:Pseudopodia / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism*; D000099317:Hippo Kinases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; D060588:LIM Domain Proteins; D017346:Protein Serine-Threonine Kinases; D019061:src-Family Kinases; C102084:Ldb1 protein, mouse; C491976:Lmo4 protein, mouse; C402650:SLK protein, mouse; D000099317:Hippo Kinases
keywords: LMO4; Ldb1; Migration; SLK; Ste20-like kinase; c-Src