A role of STAT3 in Rho GTPase-regulated cell migration and proliferation.
Rho family GTPases and STAT3 act as mediators of cytokine and growth factor signaling in a variety of cellular functions involved in inflammation, tumorigenesis, and development. In the course of searching for their functional connections, we found by using STAT3 knock-out mouse embryonic fibroblasts that RhoA, Rac1, and Cdc42 could cause nonspecific activation of STAT3 promoter-driven luciferase reporter in the absence of STAT3, raising concerns to a body of literature where STAT3 was associated with Rho GTPases based on the reporter system. We also found that although active RhoA, Rac1, and Cdc42 could all mediate Ser-727 and Tyr-705 phosphorylation and nuclear translocation of STAT3, the Rho GTPases were able to induce STAT3 activation independently of the interleukin-6 autocrine pathway, and active RhoA, Rac1, or Cdc42 could not form a stable complex with STAT3 as previously suggested, indicating an unappreciated mechanism of STAT3 activation by the Rho GTPases. The RhoA-induced STAT3 activation partly depended on Rho-associated kinase (ROK) and involved multiple effector signals as revealed by the examination of effector domain mutants of RhoA. Genetic deletion of STAT3 led to a loss of response to RhoA in myosin light chain phosphorylation and actin stress fiber induction but sensitized the cells to RhoA or ROK-stimulated cell migration. STAT3 was required for the RhoA-induced NF-kappaB and cyclin D1 transcription and was involved in NF-kappaB nuclear translocation. Furthermore, loss of STAT3 expression inhibited RhoA-promoted cell proliferation and blocked RhoA or ROK induced anchorage-independent growth. These phenotypic changes in STAT3-/- cells could be rescued by reconstituting STAT3 gene. Our studies carried out in STAT3 null cells demonstrate unambiguously that STAT3 represents an essential effector pathway of Rho GTPases in regulating multiple cellular functions including actin cytoskeleton reorganization, cell migration, gene activation, and proliferation.
Debidda
Marcella
M
Division of Experimental Hematology, Children's Hospital Research Foundation, University of Cincinnati, Cincinnati, Ohio 45229, USA.
Wang
Lei
L
Zang
Heesuk
H
Poli
Valeria
V
Zheng
Yi
Y
D000199:Actins / Q000378:metabolism; D021581:Active Transport, Cell Nucleus; D000818:Animals; D002465:Cell Movement; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D005347:Fibroblasts / Q000378:metabolism; D017353:Gene Deletion; D017930:Genes, Reporter; D015151:Immunoblotting; D007249:Inflammation; D015850:Interleukin-6 / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009154:Mutation; D018994:Myosin Light Chains / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D012190:Retroviridae / Q000235:genetics; D050796:STAT3 Transcription Factor; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D015534:Trans-Activators / Q000502:physiology*; D014443:Tyrosine / Q000737:chemistry; D014945:Wound Healing; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D000199:Actins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D018994:Myosin Light Chains; D016328:NF-kappa B; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D019938:Cyclin D1; D014443:Tyrosine; D012694:Serine; D008156:Luciferases; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein