title: A complex between FAK, RACK1, and PDE4D5 controls spreading initiation and cancer cell polarity.
abstract: A fundamental question in cell biology concerns how cells respond to their environment by polarizing after sensing directional cues. This requires the differential localization of protein complexes in cells, and it is important to identify and understand how these complexes function. Here we describe a novel "direction-sensing" pathway that links the integrin effector focal adhesion kinase (FAK), the molecular scaffold protein RACK1, and activity of one of its client proteins, PDE4D5, a cAMP-degrading phosphodiesterase. The complex is recruited to nascent adhesions and promotes cell polarity. We identify FAK FERM domain residues whose mutation impairs RACK1 binding. When re-expressed in cancer cells in which endogenous fak is deleted by Cre-lox-mediated recombination, the RACK1-binding-impaired FAK mutant protein does not support formation of nascent actin adhesion structures as cells spread. These cancer cells, like FAK-deficient cells, cannot undergo directional responses, including wound-induced polarization or chemotactic invasion into three-dimensional matrix gels. We show that RACK1 serves as the molecular bridge linking FAK to the recruitment of PDE4D5. FAK/RACK1/PDE4D5 is a novel 'direction-sensing' complex that acts to recruit specific components of the cAMP second-messenger system to nascent integrin adhesions and to the leading edge of polarizing cells.
authors.affiliation: Edinburgh Cancer Research UK Centre, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road South, Edinburgh EH4 2XR, UK.
authors.forename: Bryan
authors.initials: B
authors.lastname: Serrels
authors.forename: Emma
authors.initials: E
authors.lastname: Sandilands
authors.forename: Alan
authors.initials: A
authors.lastname: Serrels
authors.forename: George
authors.initials: G
authors.lastname: Baillie
authors.forename: Miles D
authors.initials: MD
authors.lastname: Houslay
authors.forename: Valerie G
authors.initials: VG
authors.lastname: Brunton
authors.forename: Marta
authors.initials: M
authors.lastname: Canel
authors.forename: Laura M
authors.initials: LM
authors.lastname: Machesky
authors.forename: Kurt I
authors.initials: KI
authors.lastname: Anderson
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Frame
mesh_terms: D016764:Cell Polarity; D002633:Chemotaxis; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3 / Q000378:metabolism*; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009369:Neoplasms / Q000473:pathology*; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*
chemical_list: D009363:Neoplasm Proteins; C419368:RACK1 protein, human; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D051416:Focal Adhesion Protein-Tyrosine Kinases; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; C517376:PDE4D protein, human; D019204:GTP-Binding Proteins