Figure 2. Regulation of TIMP-2 expression in PC12 cells.
A) Live-labeling immunocytochemically was performed to detect cell surface TIMP-2 expression. TIMP-2 was not detected on the cell surface of proliferating cells maintained in 15% serum (1) or after 12 hours of serum deprivation (8). Otherwise, cell surface TIMP-2 expression was present in response to all growth factor treatments. TIMP-2 expression was even up-regulated in the absence of exogenous growth factors (2–7). B) Cells were permeabilized with Triton X-100 to detect intracellular TIMP-2. Although no TIMP-2 was detected in proliferating cells (1), TIMP-2 expression was up-regulated by serum depletion (8). Expression was further up-regulated by growth factor treatment. In all cases, TIMP-2 expression was greater intracellularly than on the cell surface. TIMP-2 expression is particularly enriched in the soma and neuritic processes of NGF differentiated cells. Scale bar = 25 μm.