title: Activation of H-Ras in the endoplasmic reticulum by the RasGRF family guanine nucleotide exchange factors.
abstract: Recent findings indicate that in addition to its location in the peripheral plasma membrane, H-Ras is found in endomembranes like the endoplasmic reticulum and the Golgi complex. In these locations H-Ras is functional and can efficiently engage downstream effectors, but little is known about how its activation is regulated in these environments. Here we show that the RasGRF family exchange factors, both endogenous and ectopically expressed, are present in the endoplasmic reticulum but not in the Golgi complex. With the aid of H-Ras constructs specifically tethered to the plasma membrane, endoplasmic reticulum, and Golgi complex, we demonstrate that RasGRF1 and RasGRF2 can activate plasma membrane and reticular, but not Golgi-associated, H-Ras. We also show that RasGRF DH domain is required for the activation of H-Ras in the endoplasmic reticulum but not in the plasma membrane. Furthermore, we demonstrate that RasGRF mediation favors the activation of reticular H-Ras by lysophosphatidic acid treatment whereas plasma membrane H-Ras is made more responsive to stimulation by ionomycin. Overall, our results provide the initial insights into the regulation of H-Ras activation in the endoplasmic reticulum.
authors.affiliation: Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Departamento de Biología Molecular, Unidad de Biomedicina de la Universidad de Cantabria-CSIC, Santander 39011, Spain.
authors.forename: Imanol
authors.initials: I
authors.lastname: Arozarena
authors.forename: David
authors.initials: D
authors.lastname: Matallanas
authors.forename: María T
authors.initials: MT
authors.lastname: Berciano
authors.forename: Victoria
authors.initials: V
authors.lastname: Sanz-Moreno
authors.forename: Fernando
authors.initials: F
authors.lastname: Calvo
authors.forename: María T
authors.initials: MT
authors.lastname: Muñoz
authors.forename: Gustavo
authors.initials: G
authors.lastname: Egea
authors.forename: Miguel
authors.initials: M
authors.lastname: Lafarga
authors.forename: Piero
authors.initials: P
authors.lastname: Crespo
mesh_terms: D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005727:Ganglia, Spinal; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006624:Hippocampus; D006801:Humans; D008297:Male; D009474:Neurons / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020663:ras Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D020666:ras-GRF1 / Q000737:chemistry / Q000378:metabolism*
chemical_list: C504490:RASGRF2 protein, human; C504492:Rasgrf2 protein, rat; D020663:ras Guanine Nucleotide Exchange Factors; D020666:ras-GRF1; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)