title: Grb7 binds to Hax-1 and undergoes an intramolecular domain association that offers a model for Grb7 regulation.
abstract: Adaptor proteins mediate signal transduction from cell surface receptors to downstream signaling pathways. The Grb7 protein family of adaptor proteins is constituted by Grb7, Grb10, and Grb14. This protein family has been shown to be overexpressed in certain cancers and cancer cell lines. Grb7-mediated cell migration has been shown to proceed through a focal adhesion kinase (FAK)/Grb7 pathway, although the specific participants downstream of Grb7 in cell migration signaling have not been fully determined. In this study, we report that Grb7 interacts with Hax-1, a cytoskeletal-associated protein found overexpressed in metastatic tumors and cancer cell lines. Additionally, in yeast 2-hybrid assays, we show that the interaction is specific to the Grb7-RA and -PH domains. We have also demonstrated that full-length Grb7 and Hax-1 interact in mammalian cells and that Grb7 is tyrosine phosphorylated. Isothermal titration calorimetry measurements demonstrate the Grb7-RA-PH domains bind to the Grb7-SH2 domain with micromolar affinity, suggesting full-length Grb7 can exist in a head-to-tail conformational state that could serve a self-regulatory function.
authors.affiliation: Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM 88003, USA.
authors.forename: Sharareh
authors.initials: S
authors.lastname: Siamakpour-Reihani
authors.forename: Tabitha A
authors.initials: TA
authors.lastname: Peterson
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Bradford
authors.forename: Haroula J
authors.initials: HJ
authors.lastname: Argiros
authors.forename: Laura Lowell
authors.initials: LL
authors.lastname: Haas
authors.forename: Siamee N
authors.initials: SN
authors.lastname: Lor
authors.forename: Zachary M
authors.initials: ZM
authors.lastname: Haulsee
authors.forename: Anne M
authors.initials: AM
authors.lastname: Spuches
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Johnson
authors.forename: Larry R
authors.initials: LR
authors.lastname: Rohrschneider
authors.forename: Charles Brad
authors.initials: CB
authors.lastname: Shuster
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Lyons
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D051382:GRB7 Adaptor Protein / Q000737:chemistry* / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D010766:Phosphorylation; D019000:Phosphotyrosine; D011485:Protein Binding; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014162:Transfection; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C104759:HAX1 protein, human; D051382:GRB7 Adaptor Protein; D019000:Phosphotyrosine