Axon regeneration inhibitors enhance SRF mediated gene activity. (A) Reportergene assays were performed using a c-Fos derived construct containing a TCF and SRF (“TS”), TCF (“Tm”) or SRF binding site (“mS”). (B) Myelin, Nogo and CSPGs enhance TCF-SRF gene activity as revealed by the “TS” reportergene construct. (C) Mutating the TCF or SRF binding sites abolished induction upon a 2 h stimulation with either axon regeneration inhibitor. (D) The signaling cascade underlying myelin, Nogo and CSPG mediated TCF-SRF promoter activity involves MAP kinases and to some extent Rho-GTPases. MAP kinase signaling was blocked by PD-98059. Rho-GTPase signaling was inhibited via application of ToxB (all Rho-GTPases), C3 (RhoA only), or Y-27632 (targeting ROCK). PKA signaling, interfered with by Rp-cAMPS incubation, was dispensable for signaling to SRF. Numbers in bars indicate independent cell cultures analyzed.