Signal pathway changes in MMP-28 treated DRG cultures. A) Western blot analysis of pErbB-2, pErbB3, pPI3K (p55/p85) and phosphoMAPK in rat DRG co-cultures at 0, 1, 5, 10, 15, and 20 minutes following addition of fresh media with or without 10 nM MMP-28. Equal protein loading was determined by Ponceau-S staining of the membrane (not shown) and Coomassie staining of a parallel, equally loaded gel. B) Immunofluorescence of pErbB3 in DRG co-cultures 20 minutes after addition of fresh media containing 10 nM MMP-28 preincubated with 30 nM rabbit IgG, pAb180 or pAb183. Blue:DAPI, Red:pErbB3, Green:Acetylated C,D) Determination of proliferation in DRG co-cultures following MMP-28 treatment using PCNA. C) Relative fluorescence units were counted in 14 day myelinating cultures in control and treated samples. D) Percent of proliferating cells after 2 days in culture was determined by counting PCNA positive nuclei. N = 3, ± SD.