Farnesyltransferase inhibitors disrupt EGF receptor traffic through modulation of the RhoB GTPase

Abstract

The Rho family of small GTPases play a pivotal role in the dynamic regulation of the actin cytoskeleton. Recent studies have suggested that these signalling proteins also have wide-ranging functions in membrane trafficking pathways. The Rho family member RhoB was shown to localise to vesicles of the endocytic compartment, suggesting a potential function in regulation of endocytic traffic. In keeping with this, we have previously shown that expression of active RhoB causes a delay in the intracellular trafficking of the epidermal growth factor (EGF) receptor; however, the site of action of RhoB within the endocytic pathway is still unknown. RhoB exists as two prenylated forms in cells: geranylgeranylated RhoB (RhoB-GG) and farnesylated RhoB (RhoB-F). Here we use farnesyltransferase inhibitors (FTIs) to show that prenylation specifies the cellular localisation of RhoB. RhoB-GG localises to multivesicular late endosomes and farnesylated RhoB (RhoB-F) localises to the plasma membrane. The gain of endosomal RhoB-GG elicited by FTI treatment reduces sorting of EGF receptor to the lysosome and increases recycling to the plasma membrane. Ultrastructural analysis shows that activation of RhoB through drug treatment or mutation has no effect the sorting of receptor into late endosomes, but instead inhibits the subsequent transfer of late endosomal receptor to the lysosome.

ROCK I-mediated activation of NF-κB by RhoB

“…It also has a unique pattern of cellular distribution. It has been localized to specialized membrane compartments including the Golgi, endosomal vesicles, and the multivesicular body (MVB) [3,4]. This localization is consistent with several studies which suggest an important role for RhoB in endosome-mediated trafficking of growth factor receptors [4,5].…”

“…RhoB has been localized to the limiting membrane of the mammalian MVB [4], while Bcr interacts with subunits of the ESCRT sorting complexes that are found on the same membrane [25,33]. TSG101 is a subunit of the ESCRT complex that has been shown to directly interact with Bcr [25].…”

Lovastatin Enhances Clearance of Apoptotic Cells (Efferocytosis) with Implications for Chronic Obstructive Pulmonary Disease

“…3, C and D). It is important to note that farnesyltransferase inhibitors may increase the production of geranylgeranylated proteins, presumably by shunting excess FPP to GGPP (56). This suggests that farnesyltransferase inhibitors may not solely act by decreasing farnesylated proteins, but instead they may also change the balance in favor of geranylgeranylated proteins.…”

Farnesylated RhoB inhibits radiation-induced mitotic cell death and controls radiation-induced centrosome overduplication

“…Recent works of Wherlock 28 has demonstrated that, in HeLa cells, RhoB is localized in the plasma membrane and vesicles. FTI treatment of these cells caused a loss of RhoB plasma membrane staining, suggesting that RhoB-F may be localized to the plasma membrane, while RhoB-GG resides in the endocytic compartment.…”