Brain-Derived Neurotrophic Factor Induces Matrix Metalloproteinase 9 Expression in Neurons via the Serum Response Factor/c-Fos Pathway

Abstract

Brain-derived neurotrophic factor (BDNF) plays a pivotal role in the regulation of the transcription of genes that encode proplasticity proteins. In the present study, we provide evidence that stimulation of rat primary cortical neurons with BDNF upregulates matrix metalloproteinase 9 (MMP-9) mRNA and protein levels and increases enzymatic activity. The BDNF-induced MMP-9 transcription was dependent on extracellular signal-regulated kinase 1/2 (ERK1/2) pathway and c-Fos expression. Overexpression of AP-1 dimers in neurons led to MMP-9 promoter activation, with the most potent being those that contained c-Fos, whereas knockdown of endogenous c-Fos by small hairpin RNA (shRNA) reduced BDNF-mediated MMP-9 transcription. Additionally, mutation of the proximal AP-1 binding site in the MMP-9 promoter inhibited the activation of MMP-9 transcription. BDNF stimulation of neurons induced binding of endogenous c-Fos to the proximal MMP-9 promoter region. Furthermore, as the c-Fos gene is a known target of serum response factor (SRF), we investigated whether SRF contributes to MMP-9 transcription. Inhibition of SRF and its cofactors by either overexpression of dominant negative mutants or shRNA decreased MMP-9 promoter activation. In contrast, MMP-9 transcription was not dependent on CREB activity. Finally, we showed that neuronal activity stimulates MMP-9 transcription in a tyrosine kinase receptor B (TrkB)-dependent manner.

ACKNOWLEDGMENTS

This research was supported by the Foundation for Polish Science, Homing Program (K.K.) and a Marie Curie International Reintegration Grant within the 7th European Community Framework Programme under grant agreement number 230992, EpiTarGene (K.K.).

We thank Michal Hetman for critically reading the manuscript and Paul Herring, Marcin Rylski, and Marta Wisniewska for the reagents used in this study.

K.K. designed and performed the experiments and analyzed the data. B.K. performed the experiments and analyzed the data. E.R. performed the experiments. J.J. and A.R.M. designed, constructed, and tested shRNA c-Fos. B.K., K.K., and L.K. wrote the paper. K.K. and L.K. supervised the project.