Expression of the membrane-type 3 matrix metalloproteinase (MT3-MMP) in human brain tissues.

Membrane-type 3 matrix metalloproteinase (MT3-MMP) is a novel MT-MMP which has a transmembrane domain at the C terminus, and mediates activation of pro-gelatinase A, just as does MT1-MMP. Previously, we reported that MT1-MMP was expressed on microglial cells only in the white matter [Yamada T, Yoshiyama Y, Sato H, Seiki M, Shinagawa A, Takahashi M (1995) Acta Neuropathol 90:421-424]. In the present study of both non-neurological and Alzheimer brain tissues, we examined the localization of MT3-MMP by immunohistochemistry. Anti-MT3-MMP antibodies gave positive staining of microglial cells in all brain tissues. Positively stained microglia were found not only in the white matter but also in the gray matter. Reverse transcriptase-polymerase chain reaction for MT3-MMP mRNA showed the same amount of expression in gray and white matters, while that for gelatinase A and MT1-MMP mRNA expressed much higher in the white matter than in the gray matter. These results suggest that MT3-MMP may play a role on microglial cells, although its role may be different from MT1-MMP in the brain.