Figure 5. Syx5 suppression in human cells decreases copper accumulation but does not affect rate of turnover.

Wild-type (GM2069; A) and ATP7A deficient (Me32a; B) human cell lines were exposed to control (squares) or Syx5 (circles) siRNA for 48 h. Syx5 gene expression levels relative to wild-type were 22–46% for GM2069, and 23n45% for Me32a cells. Copper accumulation was then measured with ⁶⁴Cu following 1–24 h exposure to 2 µM copper. Values are mean with s.e.m. of six replicates over two experiments. Non-linear regression analysis demonstrated copper accumulation in GM2069 cells (A) was significantly reduced following suppression of Syx5 (F = 108.0, P<0.0001). Linear regression analysis demonstrated copper accumulation was also significantly reduced in Me32a cells (B) following suppression of Syx5 (F = 44.1, P<0.0001). Rate of copper turnover of the radioisotope ⁶⁴Cu was measured in wild-type (GM2069; C) and ATP7A deficient (Me32a; D) human cell lines. Cells were treated with control (squares) or Syx5 (circles) siRNA and exposed to 2 µM copper for 24 h, then returned to basal media for 2–8 h. Data are expressed as a percentage of copper accumulation at Time 0 and expressed as mean with s.e.m. of nine replicates over three experiments. Linear regression analysis shows that the rate of copper turnover was not significantly altered by Syx5 suppression.