title: SP-1 regulation of MMP-9 expression requires Ser586 in the PEST domain.
abstract: Rac1, a small GTPase, regulates macrophage MMP (matrix metalloproteinase)-9 in an ERK (extracellular-signal-regulated kinase)- and SP (specificity protein)-1-dependent manner. SP-1 contains a PEST (Pro-Glu-Ser-Thr) domain that may modulate protein stability. We hypothesize that Thr578, Ser586 and/or Ser587 in the PEST domain are required for SP-1 stability and MMP-9 expression secondary to activation of ERK, a serine/threonine kinase. We determined the effects of Rac1 and ERK on MMP-9 expression driven by SP-1WT (wild-type) and the SP-1 mutants T578A, S586A and S587A. Expression of WT and mutant SP-1 increased MMP9 promoter activity in alveolar macrophages. However, constitutively active Rac1 suppressed MMP9 promoter activity in cells expressing SP-1WT, SP-1T578A and SP-1S587A, but not SP-1S586A. Furthermore, constitutive ERK activation, which was inhibited by Rac1, significantly increased MMP9 transcription in cells expressing SP-1WT, but not SP-1S586A. As Rac1 activation and ERK inactivation increased degradation of SP-1WT and not SP-1S586A, the results of the present study suggest that SP-1 stability mediated at Ser586 regulates MMP9 transcription. Ex vivo, alveolar macrophages obtained from patients with asbestosis had less MMP-9 expression that was associated with decreased SP-1 expression and ERK activation. These observations demonstrate that Ser586 in the PEST domain of SP-1 is important for MMP9 gene expression in alveolar macrophages and highlight the importance of these proteins in pulmonary fibrosis.
authors.affiliation: Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA.
authors.forename: Shubha
authors.initials: S
authors.lastname: Murthy
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Ryan
authors.forename: A Brent
authors.initials: AB
authors.lastname: Carter
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D015153:Blotting, Western; D047369:Chromatin Immunoprecipitation; D024202:Electrophoretic Mobility Shift Assay; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D016676:Macrophages, Alveolar / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D009479:Neuropeptides / Q000502:physiology; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012694:Serine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D055815:Young Adult; D020744:rac GTP-Binding Proteins / Q000502:physiology; D020830:rac1 GTP-Binding Protein
chemical_list: D009479:Neuropeptides; D012333:RNA, Messenger; C484602:Rac1 protein, mouse; D016329:Sp1 Transcription Factor; D012694:Serine; D048049:Extracellular Signal-Regulated MAP Kinases; D020780:Matrix Metalloproteinase 9; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein