Matrix metalloproteinase-3 induction in rat brain astrocytes: focus on the role of two AP-1 elements
Kwang Soo Kim1, Hee Young Kim, Eun-Hye Joe
1Department of Pharmacology and Chronic Inflammatory Disease Research Center, Ajou University School of Medicine, Suwon, Korea 442-721.
Abstract:
Many brain cells secrete MMPs (matrix metalloproteinases), and increased or misregulated MMP levels are found in neurodegenerative disorders. Here we report that MMP-3 transcription and protein secretion were increased in rat brain astrocytes stimulated with lipopolysaccharide, gangliosides or interferon-gamma. Sequential deletion of the MMP-3 promoter revealed that sequences between -0.5 kb and the start codon were crucial for the transcriptional induction of MMP-3. In addition, experiments using pharmacological inhibitors of individual mitogen-activated protein kinases revealed that MMP-3 induction and promoter activity involved Jun N-terminal kinase, a representative upstream signal of AP-1 (activator protein-1). Sequence analyses of the region of the MMP-3 promoter 500 bp from the start codon indicated the presence of three AP-1 binding sequences. Among them, electrophoretic-mobility-shift assays as well as site-directed mutagenesis of individual AP-1 sequences revealed that distal and middle, but not proximal, sequences largely mediated its induction. Together, these results indicate that AP-1 could control MMP-3 induction in brain astrocytes and that its regulation through specific AP-1 elements could be exploited in the treatment of brain pathologies in which increased expression of MMP-3 plays crucial roles.
Insights
Matrix metalloproteinases (MMPs) are implicated in neurodegeneration. This study found that activator protein-1 (AP-1) controls matrix metalloproteinase-3 (MMP-3) induction in brain astrocytes, offering potential therapeutic targets for brain pathologies.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- Matrix metalloproteinases (MMPs) are enzymes involved in extracellular matrix remodeling.
- Dysregulated MMP levels, particularly MMP-3, are associated with neurodegenerative diseases.
- Brain astrocytes play a role in neuroinflammation and disease pathogenesis.
Purpose of the Study:
- To investigate the transcriptional regulation of MMP-3 in rat brain astrocytes.
- To identify the signaling pathways and promoter elements involved in MMP-3 induction.
- To explore potential therapeutic targets for neurodegenerative disorders involving MMP-3.
Main Methods:
- Stimulation of rat brain astrocytes with lipopolysaccharide, gangliosides, and interferon-gamma.
- Analysis of MMP-3 promoter activity using sequential deletion constructs.
- Pharmacological inhibition of mitogen-activated protein kinases (MAPKs).
- Electrophoretic-mobility-shift assays and site-directed mutagenesis to study AP-1 binding sites.
Main Results:
- MMP-3 transcription and secretion were significantly increased in stimulated astrocytes.
- A region between -0.5 kb and the start codon of the MMP-3 promoter was crucial for induction.
- Jun N-terminal kinase (JNK) signaling pathway and activator protein-1 (AP-1) were involved in MMP-3 induction.
- Distal and middle AP-1 binding sites within the MMP-3 promoter were key mediators of induction.
Conclusions:
- Activator protein-1 (AP-1) plays a critical role in controlling MMP-3 induction in brain astrocytes.
- Specific AP-1 elements within the MMP-3 promoter are essential for its transcriptional regulation.
- Targeting AP-1-mediated MMP-3 regulation presents a potential therapeutic strategy for neurodegenerative diseases.
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