Cdc42 and Rac1 activity is reduced in human pheochromocytoma and correlates with FARP1 and ARHGEF1 expression. Issue 4 (April 2016)

• Record Type: Journal Article
• Authors: Croisé, Pauline; Houy, Sébastien; Gand, Mathieu; Lanoix, Joël; Calco, Valérie; Tóth, Petra; Brunaud, Laurent; Lomazzi, Sandra; Paramithiotis, Eustache; Chelsky, Daniel; Ory, Stéphane; Gasman, Stéphane
• Is Part Of: Endocrine-related cancer. Volume 23:Issue 4(2016)
• Page Start: 281
• Page End: 293
• Publication Date: 2016-04
• Subjects: Rho-GTPases -- pheochromocytoma -- mass spectrometry -- Rho-GEF; Endocrine glands -- Cancer -- Periodicals; Endocrinology -- Periodicals; Cancer -- Endocrine aspects -- Periodicals; 616.9944005
• DOI: 10.1530/ERC-15-0502
• Languages: English
• ISSNs: 1351-0088

Abstract

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.