Modulation of Muscle Regeneration, Myogenesis, and Adipogenesis by the Rho Family Guanine Nucleotide Exchange Factor GEFT

Abstract

Rho family guanine nucleotide exchange factors (GEFs) regulate diverse cellular processes including cytoskeletal reorganization, cell adhesion, and differentiation via activation of the Rho GTPases. However, no studies have yet implicated Rho-GEFs as molecular regulators of the mesenchymal cell fate decisions which occur during development and repair of tissue damage. In this study, we demonstrate that the steady-state protein level of the Rho-specific GEF GEFT is modulated during skeletal muscle regeneration and that gene transfer of GEFT into cardiotoxin-injured mouse tibialis anterior muscle exerts a powerful promotion of skeletal muscle regeneration in vivo. In order to molecularly characterize this regenerative effect, we extrapolate the mechanism of action by examining the consequence of GEFT expression in multipotent cell lines capable of differentiating into a number of cell types, including muscle and adipocyte lineages. Our data demonstrate that endogenous GEFT is transcriptionally upregulated during myogenic differentiation and downregulated during adipogenic differentiation. Exogenous expression of GEFT promotes myogenesis of C2C12 cells via activation of RhoA, Rac1, and Cdc42 and their downstream effector proteins, while a dominantnegative mutant of GEFT inhibits this process. Moreover, we show that GEFT inhibits insulin-induced adipogenesis in 3T3L1 preadipocytes. In summary, we provide the first evidence that the Rho family signaling pathways act as potential regulators of skeletal muscle regeneration and provide the first reported molecular mechanism illustrating how a mammalian Rho family GEF controls this process by modulating mesenchymal cell fate decisions.

Bves directly interacts with GEFT, and controls cell shape and movement through regulation of Rac1/Cdc42 activity

“…Bves interacts with GEFT, which has previously been shown to affect cell proliferation, foci formation (17), neurite outgrowth (18,19), differentiation, and skeletal muscle regeneration (20), presumably through modulation of the Rho GTPase activity. The motility of cells is controlled by Rho GTPases through regulation of filopodial and lamellipodial extension, as well as polymerization of actin (22).…”

“…As both Bves and GEFT are highly expressed in muscle (2,6,20,26), we next examined their localization in mouse hindlimb muscle, the heart, and intestinal smooth muscle. As shown in Fig.…”

“…GEF proteins modulate activity of small GTPases, specifically the Rho family of GTPases, Rac1 and Cdc42, in the case of GEFT (17)(18)(19)(20). GEFs stimulate the exchange of GDP for GTP, thereby activating Rho small GTPases.…”

Cytohesin-2/ARNO, through Its Interaction with Focal Adhesion Adaptor Protein Paxillin, Regulates Preadipocyte Migration via the Downstream Activation of Arf6

“…It is known that adipogenesis is regulated by activities of small GTP-binding proteins (56,57). For example, RhoA regulates adipogenesis (37) and maintains the cell morphology of primary mesenchymal stem cells.…”

RAGE Expression in Rhabdomyosarcoma Cells Results in Myogenic Differentiation and Reduced Proliferation, Migration, Invasiveness, and Tumor Growth

“…49 In L6 myoblasts, the , and TE671/RAGE (R) cells were cultivated in GM for 24 hours or in DM for 24 or 72 hours and processed for detection of phosphorylated and total p38 MAPK by Western blotting. C: TE671/wt (wt), TE671/RAGE⌬cyto (⌬), and TE671/RAGE (R) cells were cultivated in DM for 30 minutes or 24 hours in the absence or presence of added HMGB1 to 100 nmol/L and processed for detection of phosphorylated and total p38 MAPK.…”