Metallothionein‐dependent regulation of the abundance of the labile intracellular pool of zinc in 3T3 cells

Abundance of the labile intracellular pool of zinc critically influences cell proliferation and apoptosis. Homeostasis of the labile intracellular pool of zinc remains to be delineated. The objective of this study was to establish the role of metallothionein (MT) in the homeostasis of the labile intracellular pool of zinc. MT1 was first cloned into pEGSH and subsequently transfected into ER‐NIH 3T3 cells. ER‐NIH 3T3 (3T3; the control), ER‐NIH 3T3:pEGSH (3T3pEGSH; the plasmid control), and ER‐NIH 3T3:pEGSH‐MT1 (3T3MT1) cells were cultured in DMEM containing 10% FBS and L‐Gln at 37°C in 5% CO 2 for 6 days (1.0 × 10 5 cells/T75). MT1 mRNA abundance in 3T3MT1 cells was significantly higher than in 3T3 (2‐folds) and 3T3pEGSH (3‐folds) cells. MT1 protein level in 3T3MT1 cells was significantly increased compared to its level in 3T3 (1.9‐folds) and 3T3pEGSH (1.4‐folds) cells. 3T3MT1 cells also contained more total zinc than 3T3 (40%) and 3T3pEGSH (20%) cells. The labile intracellular pool of zinc in 3T3MT1 cells was clearly more abundant than in the controls. In summary, higher MT1 expression increased the abundance of the labile intracellular pool of zinc in 3T3 cells, demonstrating that MT1 plays a direct role in the homeostasis of the labile intracellular pool of zinc. (Supported by NSERC)