These observations are consistent with a recent report describing a role for mDia2 DIAPH3 in nucleation of actin filaments in both filopodia and lamellipodia. Notably, our prior quanti Volasertib clinical tative proteomics study identified a cohort of actin cyto skeleton regulators that were up regulated in caveolar lipid raft microdomains of PDGF treated SMC. Given the localization of activated PDGFR, actin regulators and DIAPH3 to lipid rafts, they support the functional importance of such microdomains as sites of integration for signals that regu late cell morphology and motility. The mechanisms underlying regulation of DIAPH3 e pression are largely une plored. Our findings showed decreased e pression of DIAPH3 in PDGF treated SMC following pharmacologic inhibition of either JUN or MYC activity.

Interestingly, the transcriptional co activator Yes associated protein has been shown to promote DIAPH3 mRNA e pression in fibroblasts and to interact functionally with both JUN and MYC. Moreover, YAP is known to be upregulated in vascular SMC e posed to PDGF, and was found to be necessary for PDGF mediated SMC proliferation. Taken together, these findings are consistent with a direct role for MYC and or JUN AP 1 in transcription of the DIAPH3 gene. Conclusions In summary, our results implicate MYC and JUN AP 1 as key regulators of normal visceral SMC proliferation and migration, and provide the first evidence of a PDGF sensitive MYC regulated network in any cell type.

These findings imply that MYC is a novel target for pharmacological intervention, not only in fibroprolifera tive e pansion of smooth muscle in hollow organs, but also in cancers in which PDGFR dependent signaling and or MYC activation are drivers of tumor progression. Although transcription factors are challenging to target pharmacologically using small molecules, recent studies have reported encouraging results with inhibition of MYC in preclinical models of fibrosis and cancer. Future studies evaluating these inhibitors in models of pathologic remodeling and cancer are clearly warranted. Materials and methods Materials Recombinant human PDGF BB was from R D Systems. Antibodies to PDGFR, PDGFRB, phospho PDGFR B Tyr849 Tyr857, c Jun, phospho c Jun Ser63, c Myc, EGR1, RUN 1, DDIT3, CYR61 and GDF15 were from Cell Signaling Technology, antibodies to Myb and NFAT5 were from Epitomics, antibodies to SO 5 and GAPDH were from Santa Cruz Biotechnology, anti body to B actin was from Sigma Aldrich, antibody to DIAPH3 was a generous gift from Henry Higgs, Dartmouth Medical School.

The c Myc TF ELISA kit was from Active Motif. SP600125 and 10048 F4 were from EMD Biosciences. iScript cDNA synthesis re agents were from BioRad Laboratories. Universal PCR master mi for qRT PCR and gene specific assays were from Applied Biosystems. Primers for human tran scripts were as follows Hs00171022 m1 for C CL12. Hs00998500 g1 Brefeldin_A for sellectchem CYR61.