Serum response factor mediates nociceptor inflammatory pain plasticity

INTRODUCTION: Chronic metabotropic glutamate receptor activation in nociceptive afferents may upregulate A-Kinase Anchoring Protein 150 (AKAP150) expression and/or function. OBJECTIVES: To quantify transcriptional changes in AKAP150 expression and/or function after long-term mGluR5 agonist exposure, and identify transcriptional elements responsible. METHODS: Dorsal root ganglia (DRG) were dissected from Sprague-Dawley rats and cultured for biochemical analysis of AKAP150 expression after prolonged mGluR5 agonist exposure. Serum response factor (SRF) expression was knocked down through siRNA in cultures to demonstrate significance to AKAP150 upregulation. Serum response factor was also knocked down in vivo through intrathecal injections of specifically targeted oligonucleotides to demonstrate significance to hyperalgesic priming behavior in persistent mechanical hypersensitivity. RESULTS: Serum response factor and AKAP150 are coexpressed in TRPV1(+) DRG neurons in intact DRG. Prolonged mGluR5 agonist exposure increases SRF-dependent transcription and AKAP150 expression in a manner sensitive to protein kinase C inhibition and SRF knock down. Serum response factor in vivo knock down reduces mechanical hyperalgesic priming. CONCLUSION: Serum response factor transcription plays an important role in transcriptional upregulation of AKAP and hyperalgesic priming behavior, and may contribute to the increased role of AKAP150 in the transition from acute to chronic pain.