title: Stimulation of cellular signaling and G protein subunit dissociation by G protein betagamma subunit-binding peptides.
abstract: We previously developed peptides that bind to G protein betagamma subunits and selectively block interactions between betagamma subunits and a subset of effectors in vitro (Scott, J. K., Huang, S. F., Gangadhar, B. P., Samoriski, G. M., Clapp, P., Gross, R. A., Taussig, R., and Smrcka, A. V. (2001) EMBO J. 20, 767-776). Here, we created cell-permeating versions of some of these peptides by N-terminal modification with either myristate or the cell permeation sequence from human immunodeficiency virus TAT protein. The myristoylated betagamma-binding peptide (mSIRK) applied to primary rat arterial smooth muscle cells caused rapid activation of extracellular signal-regulated kinase 1/2 in the absence of an agonist. This activation did not occur if the peptide lacked a myristate at the N terminus, if the peptide had a single point mutation to eliminate betagamma subunit binding, or if the cells stably expressed the C terminus of betaARK1. A human immunodeficiency virus TAT-modified peptide (TAT-SIRK) and a myristoylated version of a second peptide (mSCAR) that binds to the same site on betagamma subunits as mSIRK, also caused extracellular signal-regulated kinase activation. mSIRK also stimulated Jun N-terminal kinase phosphorylation, p38 mitogen-activated protein kinase phosphorylation, and phospholipase C activity and caused Ca2+ release from internal stores. When tested with purified G protein subunits in vitro, SIRK promoted alpha subunit dissociation from betagamma subunits without stimulating nucleotide exchange. These data suggest a novel mechanism by which selective betagamma-binding peptides can release G protein betagamma subunits from heterotrimers to stimulate G protein pathways in cells.
authors.affiliation: Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, New York 14642, USA.
authors.forename: Farida
authors.initials: F
authors.lastname: Goubaeva
authors.forename: Mousumi
authors.initials: M
authors.lastname: Ghosh
authors.forename: Sundeep
authors.initials: S
authors.lastname: Malik
authors.forename: Jay
authors.initials: J
authors.lastname: Yang
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Hinkle
authors.forename: Kathy K
authors.initials: KK
authors.lastname: Griendling
authors.forename: Richard R
authors.initials: RR
authors.lastname: Neubig
authors.forename: Alan V
authors.initials: AV
authors.lastname: Smrcka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction
chemical_list: D010455:Peptides; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019204:GTP-Binding Proteins