Small GTPase Tc10 and its homologue RhoT induce N-WASP-mediated long process formation and neurite outgrowth

Abstract

Rho family small GTPases regulate multiple cellular functions through reorganization of the actin cytoskeleton. Among them, Cdc42 and Tc10 induce filopodia or peripheral processes in cultured cells. We have identified a member of the family, designated as RhoT, which is closely related to Tc10. Tc10 was highly expressed in muscular tissues and brain and remarkably induced during differentiation of C2 skeletal muscle cells and neuronal differentiation of PC12 and N1E-115 cells. On the other hand, RhoT was predominantly expressed in heart and uterus and induced during neuronal differentiation of N1E-115 cells. Tc10 exogenously expressed in fibroblasts generated actin-filament-containing peripheral processes longer than the Cdc42-formed filopodia, whereas RhoT produced much longer and thicker processes containing actin filaments. Furthermore, both Tc10 and RhoT induced neurite outgrowth in PC12 and N1E-115 cells, but Cdc42 did not do this by itself. Tc10 and RhoT as well as Cdc42 bound to the N-terminal CRIB-motif-containing portion of N-WASP and activated N-WASP to induce Arp2/3-complex-mediated actin polymerization. The formation of peripheral processes and neurites by Tc10 and RhoT was prevented by the coexpression of dominant-negative mutants of N-WASP. Thus, N-WASP is essential for the process formation and neurite outgrowth induced by Tc10 and RhoT. Neuronal differentiation of PC12 and N1E-115 cells induced by dibutyryl cyclic AMP and by serum starvation, respectively, was prevented by dominant-negative Cdc42,Tc10 and RhoT. Taken together, all these Rho family proteins are required for neuronal differentiation, but they exert their functions differentially in process formation and neurite extension. Consequently, N-WASP activated by these small GTPases mediates neuronal differentiation in addition to its recently identified role in glucose uptake.

TC10 controls human myofibril organization and is activated by the sarcomeric RhoGEF obscurin

“…Inhibition of TC10 activity by expression of a dominant-negative mutant in tail muscle cells of Ciona intestinalis larva impairs myofibril assembly. Consistent with our results in ascidia, TC10 mRNA is easily detected in striated muscle tissues from mouse and human (Abe et al, 2003;Neudauer et al, 1998). In the mouse C2C12 cell line, TC10 mRNA is detected at a moderate level in undifferentiated myoblasts.…”

“…In the mouse C2C12 cell line, TC10 mRNA is detected at a moderate level in undifferentiated myoblasts. It is then induced in myotubes and reaches high levels in terminally differentiated myotubes (Abe et al, 2003). Although JeBailey and co-workers observed TC10 mRNA transcripts in differentiated rat L6 skeletal muscle cells and 3T3-L1 adipocytes, the protein was only detected in adipocytes (JeBailey et al, 2004).…”

Temporal Dissection of β1-Integrin Signaling Indicates a Role for p130Cas-Crk in Filopodia Formation

“…Recently, Aspenstrom et al (59) showed that overexpression of constitutive active forms of the GTPases Wrch, RhoD, and Rif induced thin filopodia in porcine aortic endothelial cells, whereas overexpression of active L61Cdc42 instead induced lamellipodia. Moreover, the GTPase TC10, which is a member of the Cdc42 family, has also been shown to induce filopodia in cells (60). Interestingly, TC10 has been shown to be activated downstream of Crk in response to insulin or osmotic shock (61,62).…”

Cdc42 Regulates Cofilin during the Establishment of Neuronal Polarity

“…Interestingly, this defect was not fully penetrant. It is likely that the lack of Cdc42 can be partially compensated by other highly related GTPases, such as TC10 (Tanabe et al, 2000) or TCL/RhoT (Vignal et al, 2000;Abe et al, 2003). However, Cdc42 is clearly required for the efficient establishment of polarity and growth of the axon.…”