title: Non-prenylatable, cytosolic Rac1 alters neurite outgrowth while retaining the ability to be activated.
abstract: Rac1 is an important regulator of axon extension, cell migration and actin reorganization. Like all Rho guanine triphosphatases (GTPases), Rac1 is targeted to the membrane by the addition of a geranylgeranyl moiety, an action thought to result in Rac1 guanosine triphosphate (GTP) binding. However, the role that Rac1 localization plays in its activation (GTP loading) and subsequent activation of effectors is not completely clear. To address this, we developed a non-prenylatable emerald green fluorescent protein (EmGFP)-Rac1 fusion protein (EmGFP-Rac1(C189A)) and assessed how expressing this construct affected neurite outgrowth, Rac1 localization and activation in neuroblastoma cells. Expression of EmGFP-Rac1(C189A) increased localization to the cytosol and induced cell clustering while increasing neurite initiation. EmGFP-Rac1(C189A) expression also increased Rac1 activation in the cytosol, compared to cells expressing wild-type Rac1 (EmGFP-Rac1). These results suggest that activation of Rac1 may not require plasma membrane localization, potentially leading to differential activation of cytosolic signaling pathways that alter cell morphology. Understanding the consequences of differential localization and activation of Rho GTPases, including Rac1, could lead to new therapeutic targets for treating neurological disorders.
authors.affiliation: Texas Woman's University Department of Biology, Denton, TX 76204-5799, United States.
authors.forename: Jairus M
authors.initials: JM
authors.lastname: Reddy
authors.affiliation: Center for Research in Neurodegenerative Disease, University of Toronto, Toronto, Canada.
authors.forename: Filsy G
authors.initials: FG
authors.lastname: Samuel
authors.affiliation: Texas Woman's University Department of Biology, Denton, TX 76204-5799, United States.
authors.forename: Jordan A
authors.initials: JA
authors.lastname: McConnell
authors.affiliation: Texas Woman's University Department of Biology, Denton, TX 76204-5799, United States.
authors.forename: Cristina P
authors.initials: CP
authors.lastname: Reddy
authors.affiliation: Texas Woman's University Department of Biology, Denton, TX 76204-5799, United States.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Beck
authors.affiliation: Texas Woman's University Department of Biology, Denton, TX 76204-5799, United States. Electronic address: dhynds@twu.edu.
authors.forename: DiAnna L
authors.initials: DL
authors.lastname: Hynds
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D008148:Lovastatin / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D016501:Neurites / Q000502:physiology*; D051381:Rats; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D008148:Lovastatin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020830:rac1 GTP-Binding Protein
keywords: Geranylgeranylation; Neurite outgrowth; Prenylation; Rho GTPases; Statins; Subcellular localization