title: Cdc42 and Rac1 activity is reduced in human pheochromocytoma and correlates with FARP1 and ARHGEF1 expression.
abstract: Among small GTPases from the Rho family, Cdc42, RAC, and Rho are well known to mediate a large variety of cellular processes linked with cancer biology through their ability to cycle between an inactive (GDP-bound) and an active (GTP-bound) state. Guanine nucleotide exchange factors (GEFs) stimulate the exchange of GDP for GTP to generate the activated form, whereas the GTPase-activating proteins (GAPs) catalyze GTP hydrolysis, leading to the inactivated form. Modulation of Rho GTPase activity following altered expression of RHO-GEFs and/or RHO-GAPs has already been reported in various human tumors. However, nothing is known about the Rho GTPase activity or the expression of their regulators in human pheochromocytomas, a neuroendocrine tumor (NET) arising from chromaffin cells of the adrenal medulla. In this study, we demonstrate, through an ELISA-based activity assay, that Rac1 and Cdc42 activities decrease in human pheochromocytomas (PCCs) compared with the matched adjacent non-tumor tissue. Furthermore, through quantitative mass spectrometry (MS) approaches, we show that the expression of two RHO-GEF proteins, namely ARHGEF1 and FARP1, is significantly reduced in tumors compared with matched non-tumor tissue, whereas ARHGAP36 expression is increased. Moreover, siRNA-based knockdown of ARHGEF1 and FARP1 in PC12 cells leads to a significant inhibition of Rac1 and Cdc42 activities, respectively. Finally, a principal component analysis (PCA) of our dataset was able to discriminate PCC from non-tumor tissue and indicates a close correlation between Cdc42/Rac1 activity and FARP1/ARHGEF1 expression. Altogether, our findings reveal for the first time the importance of modulation of Rho GTPase activities and expression of their regulators in human PCCs.
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives (INCI)CNRS UPR 3212, Strasbourg, France.
authors.forename: Pauline
authors.initials: P
authors.lastname: Croisé
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives (INCI)CNRS UPR 3212, Strasbourg, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Houy
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives (INCI)CNRS UPR 3212, Strasbourg, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Gand
authors.affiliation: Caprion Proteome, Inc.Montréal, Québec, Canada.
authors.forename: Joël
authors.initials: J
authors.lastname: Lanoix
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives (INCI)CNRS UPR 3212, Strasbourg, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Calco
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives (INCI)CNRS UPR 3212, Strasbourg, France.
authors.forename: Petra
authors.initials: P
authors.lastname: Tóth
authors.affiliation: Service de Chirurgie DigestiveHépato-bilaire et Endocrinienne, CHRU Nancy, Hôpitaux de Brabois, Vandoeuvre les Nancy, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Brunaud
authors.affiliation: Centre de Ressources Biologiques (CRB)CHRU Nancy, Hôpitaux de Brabois, Vandoeuvres les Nancy, France.
authors.forename: Sandra
authors.initials: S
authors.lastname: Lomazzi
authors.affiliation: Caprion Proteome, Inc.Montréal, Québec, Canada.
authors.forename: Eustache
authors.initials: E
authors.lastname: Paramithiotis
authors.affiliation: Caprion Proteome, Inc.Montréal, Québec, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Chelsky
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives (INCI)CNRS UPR 3212, Strasbourg, France ory@inci-cnrs.unistra.fr gasman@inci-cnrs.unistra.fr.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Ory
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives (INCI)CNRS UPR 3212, Strasbourg, France ory@inci-cnrs.unistra.fr gasman@inci-cnrs.unistra.fr.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Gasman
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000378:metabolism*; D000818:Animals; D006801:Humans; D016716:PC12 Cells; D010673:Pheochromocytoma / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D064067:Rho Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: C576600:ARHGEF1 protein, human; C577227:FARP1 protein, human; C107953:RAC1 protein, human; D034741:RNA, Small Interfering; D064067:Rho Guanine Nucleotide Exchange Factors; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein
keywords: RHO-GEF; RHO-GTPases; mass spectrometry; pheochromocytoma