Ndings that -opioid receptormediated ERK activation involves CaM-dependent EGFR transactivation [51]. Accumulating evidence has shown that MMP-9 is upregulated via an AP-1-dependent manner in various cell types [25,35,52]. AP-1 is an important mediator to regulate MMP-9 gene expression upon different stimulation [38,53]. Upon stimulation, c-Jun could dimerize with c-Jun or c-Fos to form stable hom