Rho guanine nucleotide dissociation inhibitor protein (RhoGDI) inhibits exocytosis in mast cells.

Abstract

Introducing non‐hydrolysable analogues of GTP into the cytosolic compartment of mast cells results in exocytotic secretion through the activation of GTP binding proteins. The identity and mechanism of action of these proteins are not established. We have investigated the effects of Rho GDP dissociation inhibitor (RhoGDI) on exocytosis induced by guanosine 5′‐O‐(3‐thiotriphosphate) (GTP‐gamma‐S) in rat mast cells, introducing the protein into cells by means of a patch pipette and recording the progress of exocytosis by monitoring cell capacitance. To allow time for the protein to enter the cells and find its correct location, stimulation was provided 5–10 min after patch rupture by photolysing caged GTP‐gamma‐S included in the pipette solution. When bovine RhoGDI was introduced into mast cells, exocytosis was inhibited at concentrations of 200–400 nM for native protein and 800 nM to 8 microM for the recombinant form. Protein denatured by heat or N‐ethylmaleimide treatment did not inhibit. In permeabilized cells, recombinant RhoGDI increased the rate at which cells lose their ability to respond to GTP‐gamma‐S. These data demonstrate that one or more small GTP binding proteins of the Rho family has a central role in the exocytotic mechanism in mast cells.

RalA-Exocyst Interaction Mediates GTP-dependent Exocytosis

“…We showed that the interaction between RalA GTPase and the exocyst is critical for GTP-dependent exocytosis. The involvement of other GTPases (Rab3A and Rho) in GTP-dependent exocytosis has been previously suggested (12,15). The experiments using the Rab3A fragment (effector loop peptide) in mast cells (15) are now being questioned because the fragment induces Ca 2ϩ transients in mast cells, raising the possibility that its mode of action is nonspecific (52).…”

“…In particular, the Rho, Rab, and Ral families of low molecular weight proteins, which are monomeric GTPases, have been suggested as regulators of exocytosis. Rho family proteins have been proposed to regulate exocytosis in mast cells (10), because Rho GDP dissociation inhibitor (RhoGDI) (11) has been shown to inhibit GTP␥S-induced exocytosis in mast cells (12). RhoGDI is known to inhibit GDP/GTP exchange in Rho family proteins including Rho, Cdc42, and Rac (11,13,14).…”

Progressive impairment of kidneys and reproductive organs in mice lacking Rho GDIα

“…For instance, Rho GDIa caused disappearance of stress ®bers and inhibition of cell motility in Swiss 3T3 cells and 308R mouse keratinocytes (Miura et al, 1993;Takaishi et al, 1993Takaishi et al, , 1994, aected the localization of the ERM (Ezrin, Radixin, Moesin) family proteins and vinculin at the plasma membrane in MDCK cells . Exocytosis from rat mast cells (Mariot et al, 1996) and PC12 cells (Komuro et al, 1996) was inhibited by Rho GDIa, whereas receptor-mediated endocytosis of transferrin was suppressed by Rho and Rac but restored by Rho GDIa (Lamaze et al, 1996).…”

Rac and Phosphatidylinositol 3-Kinase Regulate the Protein Kinase B in FcεRI Signaling in RBL 2H3 Mast Cells

“…Recent studies indicate that Rho GTPases are also involved in activation of RBL cells (18 -21). For example, stable expression of dominant negative Rac and Cdc42 in RBL cells inhibited Fc⑀RI-mediated degranulation (22), and RhoGDI, a guanine nucleotide dissociation inhibitor that was shown to block the biological activity of Rho GTPases, inhibited regulated exocytosis from RBL cells (23).…”