Absence of PICALM results in a decreased rate of internalization and increased cell surface expression of TfR in MEFs.

<p>The level of cell surface TfR expression normalized to levels in WT cells (<b>A,C,E</b>) and the rate of TfR internalization (<b>B,D,F</b>) was measured in non-immortalized MEFs (<b>A,B</b>), immortalized MEFs (<b>C,D</b>), or PICALM shRNA knockdown WT (line 7T) MEFs (<b>E,F</b>). (<b>A</b>) Surface TfR expression in non-immortalized WT and <i>Picalm</i>^NULL MEFs. N_exp = 4. *p<0.02 compared with WT. (<b>B</b>) TfR internalization at three different time points in independently derived non-immortalized WT (lines 20, 33) and <i>Picalm</i>^NULL (lines 24, 29, 31). N_exp = 2. *p<0.04 compared with WT. (<b>C</b>) Surface TfR expression in immortalized WT and <i>Picalm</i>^NULL MEFs. N_exp = 4. *p<0.04 compared with WT. (<b>D</b>) TfR internalization in independently derived immortalized WT (lines 20T, 33T) and <i>Picalm</i>^NULL (lines 24T, 29T, 31T). N_exp = 7. *p<0.01 compared with WT. (<b>E</b>) Surface TfR expression in shRNA transduced WT MEFs. N_exp = 4. *p<0.02 compared with WT. (<b>F</b>) TfR internalization in immortalized WT (line 7T) transduced with two separate PICALM shRNA retroviruses (shRNA4, shRNA5) or a control shRNA retrovirus. N_exp = 3. *p<0.01 compared with WT. In all cases, error bars denote standard error. Two-tailed Student’s t-test was used to compare means for TfR internalization (A,C,E).