title: SHANK proteins limit integrin activation by directly interacting with Rap1 and R-Ras.
abstract: SHANK3, a synaptic scaffold protein and actin regulator, is widely expressed outside of the central nervous system with predominantly unknown function. Solving the structure of the SHANK3 N-terminal region revealed that the SPN domain is an unexpected Ras-association domain with high affinity for GTP-bound Ras and Rap G-proteins. The role of Rap1 in integrin activation is well established but the mechanisms to antagonize it remain largely unknown. Here, we show that SHANK1 and SHANK3 act as integrin activation inhibitors by sequestering active Rap1 and R-Ras via the SPN domain and thus limiting their bioavailability at the plasma membrane. Consistently, SHANK3 silencing triggers increased plasma membrane Rap1 activity, cell spreading, migration and invasion. Autism-related mutations within the SHANK3 SPN domain (R12C and L68P) disrupt G-protein interaction and fail to counteract integrin activation along the Rap1-RIAM-talin axis in cancer cells and neurons. Altogether, we establish SHANKs as critical regulators of G-protein signalling and integrin-dependent processes.
authors.affiliation: Turku Centre for Biotechnology, University of Turku, FIN-20520 Turku, Finland.
authors.forename: Johanna
authors.initials: J
authors.lastname: Lilja
authors.affiliation: University of Liverpool, Liverpool, United Kingdom.
authors.forename: Thomas
authors.initials: T
authors.lastname: Zacharchenko
authors.affiliation: Turku Centre for Biotechnology, University of Turku, FIN-20520 Turku, Finland.
authors.forename: Maria
authors.initials: M
authors.lastname: Georgiadou
authors.affiliation: Turku Centre for Biotechnology, University of Turku, FIN-20520 Turku, Finland.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Jacquemet
authors.affiliation: Turku Centre for Biotechnology, University of Turku, FIN-20520 Turku, Finland.
authors.forename: Nicola
authors.initials: N
authors.lastname: De Franceschi
authors.affiliation: Turku Centre for Biotechnology, University of Turku, FIN-20520 Turku, Finland.
authors.forename: Emilia
authors.initials: E
authors.lastname: Peuhu
authors.affiliation: Turku Centre for Biotechnology, University of Turku, FIN-20520 Turku, Finland.
authors.forename: Hellyeh
authors.initials: H
authors.lastname: Hamidi
authors.affiliation: Turku Centre for Biotechnology, University of Turku, FIN-20520 Turku, Finland.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Pouwels
authors.affiliation: Institute for Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Victoria
authors.initials: V
authors.lastname: Martens
authors.affiliation: Institute for Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Fatemeh Hassani
authors.initials: FH
authors.lastname: Nia
authors.affiliation: Institute for Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Malte
authors.initials: M
authors.lastname: Beifuss
authors.affiliation: Institute for Anatomy and Cell Biology, University of Ulm, Ulm, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Boeckers
authors.affiliation: Institute for Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Hans-Juergen
authors.initials: HJ
authors.lastname: Kreienkamp
authors.affiliation: University of Liverpool, Liverpool, United Kingdom.
authors.forename: Igor L
authors.initials: IL
authors.lastname: Barsukov
authors.affiliation: Turku Centre for Biotechnology, University of Turku, FIN-20520 Turku, Finland.|Department of Biochemistry and Food Chemistry, University of Turku, Turku, Finland.
authors.forename: Johanna
authors.initials: J
authors.lastname: Ivaska
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002448:Cell Adhesion; D002460:Cell Line; D002465:Cell Movement; D022081:Cell Surface Extensions / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D019012:Integrin beta1 / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D000072417:Protein Domains; D017208:Rats, Wistar; D016415:Sequence Alignment; D016608:Talin / Q000378:metabolism; D014452:Ubiquitins / Q000235:genetics; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D019012:Integrin beta1; D009419:Nerve Tissue Proteins; C575183:SHARPIN protein, human; D016608:Talin; D014452:Ubiquitins; C085929:RRAS protein, human; D020827:rap1 GTP-Binding Proteins; D018631:ras Proteins