title: A novel protease-activated receptor-1 interactor, Bicaudal D1, regulates G protein signaling and internalization.
abstract: Protease-activated receptor-1 (PAR1) is a G protein-coupled receptor that plays critical roles in cancer, angiogenesis, inflammation, and thrombosis. Proteolytic cleavage of the extracellular domain of PAR1 generates a tethered ligand that activates PAR1 in an unusual intramolecular mode. The signal emanating from the irreversibly cleaved PAR1 is terminated by G protein uncoupling and internalization; however, the mechanisms of PAR1 signal shut off still remain unclear. Using a yeast two-hybrid screen, we identified Bicaudal D1 (BicD1) as a direct interactor with the C-terminal cytoplasmic domain of PAR1. BICD was originally identified as an essential developmental gene associated with mRNA and Golgi-endoplasmic reticulum transport. We discovered a novel function of BicD1 in the modulation of G protein signaling, cell proliferation, and endocytosis downstream of PAR1. BicD1 and its C-terminal CC3 domain inhibited PAR1 signaling to G(q)-phospholipase C-beta through coiled-coil interactions with the cytoplasmic 8th helix of PAR1. Unexpectedly, BicD1 was also found to be a potent suppressor of PAR1-driven proliferation of breast carcinoma cells. The growth-suppressing effects of BicD1 required the ability to interact with the 8th helix of PAR1. Silencing of BicD1 expression impaired endocytosis of PAR1, and BicD1 co-localized with PAR1 and tubulin, implicating BicD1 as an important adapter protein involved in the transport of PAR1 from the plasma membrane to endosomal vesicles. Together, these findings provide a link between PAR1 signal termination and internalization through the non-G protein effector, BicD1.
authors.affiliation: Molecular Oncology Research Institute, Tufts Medical Center, and Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Swift
authors.forename: Jian
authors.initials: J
authors.lastname: Xu
authors.forename: Vishal
authors.initials: V
authors.lastname: Trivedi
authors.forename: Karyn M
authors.initials: KM
authors.lastname: Austin
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Tressel
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Lidija
authors.initials: L
authors.lastname: Covic
authors.forename: Athan
authors.initials: A
authors.lastname: Kuliopulos
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism; D019556:COS Cells; D049109:Cell Proliferation; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D005260:Female; D019204:GTP-Binding Proteins / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D051381:Rats; D044462:Receptors, Proteinase-Activated / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C109571:BICD1 protein, human; D003598:Cytoskeletal Proteins; D044462:Receptors, Proteinase-Activated; D019204:GTP-Binding Proteins