title: Rac1-MKK3-p38-MAPKAPK2 pathway promotes urokinase plasminogen activator mRNA stability in invasive breast cancer cells.
abstract: We reported previously that down-regulating or functionally blocking alphav integrins inhibits endogenous p38 mitogen-activated protein kinase (MAPK) activity and urokinase plasminogen activator (uPA) expression in invasive MDA-MB-231 breast cancer cells whereas engaging alphav integrins with vitronectin activates p38 MAPK and up-regulates uPA expression (Chen, J., Baskerville, C., Han, Q., Pan, Z., and Huang, S. (2001) J. Biol. Chem. 276, 47901-47905). Currently, it is not clear what upstream and downstream signaling molecules of p38 MAPK mediate alphav integrin-mediated uPA up-regulation. In the present study, we found that alphav integrin ligation activated small GTPase Rac1 preferentially, and dominant negative Rac1 inhibited alphav integrin-mediated p38 MAPK activation. Using constitutively active MAPK kinases, we found that both constitutively active MKK3 and MKK6 mutants were able to activate p38 MAPK and up-regulate uPA expression, but only dominant negative MKK3 blocked alphav integrin-mediated p38 MAPK activation and uPA up-regulation. These results suggest that MKK3, rather than MKK6, mediates alphav integrin-induced p38 MAPK activation. Among the potential downstream effectors of p38 MAPK, we found that only MAPK-activated protein kinase 2 affects alphav integrin-mediated uPA up-regulation significantly. Finally, using beta-globin reporter gene constructs containing uPA mRNA 3'-untranslated region (UTR) and adenosine/uridine-rich elements-deleted 3'-UTR, we demonstrated that p38 MAPK/MAPK-activated protein kinase 2 signaling pathway regulated uPA mRNA stability through a mechanism involving the adenosine/uridine-rich elements sequence in 3'-UTR of uPA mRNA.
authors.affiliation: Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Qiwei
authors.initials: Q
authors.lastname: Han
authors.forename: Jay
authors.initials: J
authors.lastname: Leng
authors.forename: Dafang
authors.initials: D
authors.lastname: Bian
authors.forename: Chitladda
authors.initials: C
authors.lastname: Mahanivong
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Carpenter
authors.forename: Zhixing K
authors.initials: ZK
authors.lastname: Pan
authors.forename: Jiahuai
authors.initials: J
authors.lastname: Han
authors.forename: Shuang
authors.initials: S
authors.lastname: Huang
mesh_terms: D020413:3' Untranslated Regions; D001483:Base Sequence; D001943:Breast Neoplasms / Q000201:enzymology* / Q000473:pathology; D017931:DNA Primers; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D048371:MAP Kinase Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics*; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D000099190:MAP-Kinase-Activated Kinase 2
chemical_list: D020413:3' Untranslated Regions; D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; D048371:MAP Kinase Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D012333:RNA, Messenger; D014568:Urokinase-Type Plasminogen Activator; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein; D000099190:MAP-Kinase-Activated Kinase 2; C482530:MAP2K3 protein, human