Figure 4.

MITF overexpression enhances STIM1 expression and activity.A, Western blot analysis for examining MITF protein levels upon MITF-M overexpression in B16 cells (N = 3). B, densitometric quantitation of MITF levels upon MITF-M overexpression as compared to control (N = 3). C, Western blot analysis for examining STIM1 protein levels upon MITF-M overexpression in B16 cells (N = 4). D, densitometric quantitation of STIM1 levels upon MITF-M overexpression as compared to control (N = 4). E, representative Ca²⁺ imaging trace of control plasmid pEGFP-N1, where “n = 40” denotes the number of cells in that particular trace. Cells were stimulated with 2 μM thapsigargin (Tg) in Ca²⁺-free buffer followed by restoration of 2 mM extracellular Ca²⁺. F, representative Ca²⁺ imaging trace of MITF-M overexpression, where “n = 49” denotes the number of cells in that particular trace. Cells were stimulated with 2 μM thapsigargin (Tg) in Ca²⁺-free buffer followed by restoration of 2 mM extracellular Ca²⁺. G, the extent of SOCE was calculated from 312 control plasmid pEGFP-N1 and 340 MITF-M–overexpressed B16 cells, which were imaged from eight independent experiments (“n = x, y” where “x” denotes total number of cells imaged and “y” denotes number of traces recorded). Data presented are mean ± S.E.M. For statistical analysis, one sample t test was performed for panel B and D, and unpaired student’s t test was performed for panel G. Here, ∗p < 0.05; ∗∗p < 0.01; ∗∗∗∗p < 0.0001. MITF, Microphthalmia-associated transcription factor; STIM1, Stromal Interaction Molecule1; SOCE, store-operated Ca2+ entry.