title: Rac2, a hematopoiesis-specific Rho GTPase, specifically regulates mast cell protease gene expression in bone marrow-derived mast cells.
abstract: Rho family GTPases activate intracellular kinase cascades to modulate transcription of multiple genes. Previous studies have examined the roles of the ubiquitously expressed Rho GTPase, Rac1, in regulation of gene expression in cell lines and implicated NF-kappaB, serum response factor, and kinase signaling pathways in this regulation. To understand the role of the closely related but hematopoiesis-specific Rho GTPase, Rac2, in regulation of gene transcription, we compared the gene expression profiles between wild-type and Rac2(-/-) bone marrow-derived mast cells. Our data demonstrate remarkable specificity in the regulation of gene expression by Rac2 versus Rac1. Microarray analysis demonstrated that expression of 38 known genes was significantly altered in Rac2(-/-) mast cells after cytokine stimulation compared with those in wild-type cells. Of these, the expression of the mouse mast cell protease 7 (MMCP-7) gene in wild-type cells was highly induced at the transcriptional level after stimulation with stem cell factor (SCF). In spite of compensatorily increased expression of Rac1 in Rac2-deficient cells, SCF-induced MMCP-7 transcription did not occur. Surprisingly, the loss of MMCP-7 induction was not due to decreased activation of NF-kappaB, a transcription factor postulated to lie downstream of Rac1 and known to play a critical role in hematopoietic cell differentiation and proliferation. However, the activities of c-Jun N-terminal kinases (JNKs) were markedly decreased in Rac2(-/-) mast cells. Our results suggest that cytokine-stimulated activation of MMCP-7 gene transcription is selectively regulated by a Rac2-dependent JNK signaling pathway in primary mast cells and imply a remarkable specificity in the regulation of transcriptional activity by these two highly related Rho GTPases.
authors.affiliation: Division of Experimental Hematology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Gu
authors.forename: Michael C
authors.initials: MC
authors.lastname: Byrne
authors.forename: Nivanka C
authors.initials: NC
authors.lastname: Paranavitana
authors.forename: Bruce
authors.initials: B
authors.lastname: Aronow
authors.forename: Jamie E
authors.initials: JE
authors.lastname: Siefring
authors.forename: Maria
authors.initials: M
authors.lastname: D'Souza
authors.forename: Heidi F
authors.initials: HF
authors.lastname: Horton
authors.forename: Lawrence A
authors.initials: LA
authors.lastname: Quilliam
authors.forename: David A
authors.initials: DA
authors.lastname: Williams
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D015151:Immunoblotting; D048031:JNK Mitogen-Activated Protein Kinases; D008407:Mast Cells / Q000201:enzymology*; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D053802:Tryptases; D015854:Up-Regulation; D020744:rac GTP-Binding Proteins / Q000378:metabolism* / Q000502:physiology*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D000097766:RAC2 GTP-Binding Protein
chemical_list: D003609:Dactinomycin; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D019009:Proto-Oncogene Proteins c-kit; D012697:Serine Endopeptidases; D019089:Stem Cell Factor; D053802:Tryptases; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins; D000097766:RAC2 GTP-Binding Protein; C509190:Tpsb2 protein, mouse; C509222:Tpsab1 protein, mouse