title: Role of the C-terminal basic amino acids and the lipid anchor of the Gγ2protein in membrane interactions and cell localization.
abstract: Heterotrimeric G proteins are peripheral membrane proteins that frequently localize to the plasma membrane where their presence in molar excess over G protein coupled receptors permits signal amplification. Their distribution is regulated by protein-lipid interactions, which has a clear influence on their activity. Gβγ dimer drives the interaction between G protein heterotrimers with cell membranes. We focused our study on the role of the C-terminal region of the Gγ2protein in G protein interactions with cell membranes. The Gγ2subunit is modified at cysteine (Cys) 68 by the addition of an isoprenyl lipid, which is followed by the proteolytic removal of the last three residues that leaves an isoprenylated and carboxyl methylated Cys-68 as the terminal amino acid. The role of Cys isoprenylation of the CAAX box has been defined for other proteins, yet the importance of proteolysis and carboxyl methylation of isoprenylated proteins is less clear. Here, we showed that not only geranylgeranylation but also proteolysis and carboxyl methylation are essential for the correct localization of Gγ2in the plasma membrane. Moreover, we showed the importance of electrostatic interactions between the inner leaflet of the plasma membrane and the positively charged C-terminal domain of the Gγ2subunit (amino acids Arg-62, Lys-64 and Lys-65) as a second signal to reach the plasma membrane. Indeed, single or multiple point mutations at Gγ2C-terminal amino acids have a significant effect on Gγ2protein-plasma membrane interactions and its localization to charged Ld (liquid disordered) membrane microdomains. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.
authors.affiliation: Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, E-07122 Palma, Balearic Islands, Spain.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Noguera-Salvà
authors.affiliation: Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, E-07122 Palma, Balearic Islands, Spain.
authors.forename: Francisca
authors.initials: F
authors.lastname: Guardiola-Serrano
authors.affiliation: Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, E-07122 Palma, Balearic Islands, Spain.
authors.forename: M Laura
authors.initials: ML
authors.lastname: Martin
authors.affiliation: Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, E-07122 Palma, Balearic Islands, Spain.
authors.forename: Amaia
authors.initials: A
authors.lastname: Marcilla-Etxenike
authors.affiliation: Sahlgrenska Cancer Center, University of Gothenburg, SE-405 30 Gothenburg, Sweden.
authors.forename: Martin O
authors.initials: MO
authors.lastname: Bergo
authors.affiliation: Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, E-07122 Palma, Balearic Islands, Spain. Electronic address: xavier.busquets@uib.es.
authors.forename: Xavier
authors.initials: X
authors.lastname: Busquets
authors.affiliation: Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, E-07122 Palma, Balearic Islands, Spain.
authors.forename: Pablo V
authors.initials: PV
authors.lastname: Escribá
mesh_terms: D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000737:chemistry*; D004224:Diterpenes / Q000378:metabolism; D044388:GTP-Binding Protein gamma Subunits / Q000032:analysis / Q000737:chemistry*; D006801:Humans; D008563:Membrane Lipids / Q000737:chemistry*; D011485:Protein Binding; D017368:Protein Prenylation
chemical_list: D004224:Diterpenes; D044388:GTP-Binding Protein gamma Subunits; D008563:Membrane Lipids; C040155:geranylgeranic acid
keywords: Carboxyl methylation; Electrostatic interactions; G protein; Geranylgeranylation; Posttranslational modifications