title: Rho Family GTPase modification and dependence on CAAX motif-signaled posttranslational modification.
abstract: Rho GTPases (20 human members) comprise a major branch of the Ras superfamily of small GTPases, and aberrant Rho GTPase function has been implicated in oncogenesis and other human diseases. Although many of our current concepts of Rho GTPases are based on the three classical members (RhoA, Rac1, and Cdc42), recent studies have revealed the diversity of biological functions mediated by other family members. A key basis for the functional diversity of Rho GTPases is their association with distinct subcellular compartments, which is dictated in part by three posttranslational modifications signaled by their carboxyl-terminal CAAX (where C represents cysteine, A is an aliphatic amino acid, and X is a terminal amino acid) tetrapeptide motifs. CAAX motifs are substrates for the prenyltransferase-catalyzed addition of either farnesyl or geranylgeranyl isoprenoid lipids, Rce1-catalyzed endoproteolytic cleavage of the AAX amino acids, and Icmt-catalyzed carboxyl methylation of the isoprenylcysteine. We utilized pharmacologic, biochemical, and genetic approaches to determine the sequence requirements and roles of CAAX signal modifications in dictating the subcellular locations and functions of the Rho GTPase family. Although the classical Rho GTPases are modified by geranylgeranylation, we found that a majority of the other Rho GTPases are substrates for farnesyltransferase. We found that the membrane association and/or function of Rho GTPases are differentially dependent on Rce1- and Icmt-mediated modifications. Our results further delineate the sequence requirements for prenyltransferase specificity and functional roles for protein prenylation in Rho GTPase function. We conclude that a majority of Rho GTPases are targets for pharmacologic inhibitors of farnesyltransferase, Rce1, and Icmt.
authors.affiliation: Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina 27599; Division of Pharmacotherapy and Experimental Therapeutics, Chapel Hill, North Carolina 27599.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Roberts
authors.affiliation: Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina 27599; Department of Pharmacology, Chapel Hill, North Carolina 27599.
authors.forename: Natalia
authors.initials: N
authors.lastname: Mitin
authors.affiliation: Department of Pharmacology, Chapel Hill, North Carolina 27599; Department of Radiation Oncology, Chapel Hill, North Carolina 27599.
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Keller
authors.affiliation: Department of Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Chenette
authors.affiliation: Department of Radiation Oncology, Chapel Hill, North Carolina 27599; Department of Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599.
authors.forename: James P
authors.initials: JP
authors.lastname: Madigan
authors.affiliation: Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina 27599.
authors.forename: Rachel O
authors.initials: RO
authors.lastname: Currin
authors.affiliation: Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina 27599; Department of Pharmacology, Chapel Hill, North Carolina 27599; Department of Radiation Oncology, Chapel Hill, North Carolina 27599; Department of Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599.
authors.forename: Adrienne D
authors.initials: AD
authors.lastname: Cox
authors.affiliation: Schering-Plough Research Institute, Kenilworth, New Jersey 07033.
authors.forename: Oswald
authors.initials: O
authors.lastname: Wilson
authors.affiliation: Schering-Plough Research Institute, Kenilworth, New Jersey 07033.
authors.forename: Paul
authors.initials: P
authors.lastname: Kirschmeier
authors.affiliation: Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina 27599; Department of Pharmacology, Chapel Hill, North Carolina 27599; Department of Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599. Electronic address: cjder@med.unc.edu.
authors.forename: Channing J
authors.initials: CJ
authors.lastname: Der
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D003545:Cysteine / Q000737:chemistry; D010450:Endopeptidases / Q000737:chemistry; D051231:Farnesyltranstransferase / Q000037:antagonists & inhibitors; D006801:Humans; D051379:Mice; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D051231:Farnesyltranstransferase; D010450:Endopeptidases; C491326:RCE1 protein, human; C491324:Rce1 protein, mouse; D020741:rho GTP-Binding Proteins; D003545:Cysteine