γ-Synuclein is a small cytoplasmic protein implicated in neurodegenerative diseases and cancer. However, the mechanism of its involvement in diseases is not clear. We studied the role of γ-synuclein in the regulation of matrix metalloproteinases in retinoblastoma cell culture. Matrix metalloproteinases play important roles in the remodeling of extracellular matrix implicated in tumor progression and in the neurodegenerative diseases. Western blot and zymography data demonstrated a moderate elevation of matrix metalloproteinases-2 and significant upregulation of matrix metalloproteinases-9 in stable cell lines overexpressing γ-synuclein. No effect of γ-synuclein overexpression on matrix metalloproteinases-1 level or activity was found. Chloramphenicol-acetyltransferase assay demonstrated that overexpression of γ-synuclein increases the efficiency of the matrix metalloproteinases-9 promoter. This increment of promoter activity may be mediated by the AP-1 binding site(s), since point mutations in one of these sites (Pr18 or Pr19) and elimination of the distal AP-1 site (Pr14) reduced the increment of promoter activity. © 2002 Elsevier Science (USA). All rights reserved.