Figure 5: TRPML-mediated currents are reduced in the lysosomes of NPC cells.

(a,b) Concentration-dependent activation of whole-endolysosome IML−L in WT (a) and NPC (b) human fibroblasts. ML-SA1 (3, 10 and 25 μM) was applied to the cytosolic sides of the vacuoles isolated from human fibroblasts. (c) Average current densities (pA/pF) of IML−L were reduced in NPC fibroblasts compared with WT cells. The current density was calculated from the current size (pA) normalized with the capacitance of the vacuole (pF). (d) Reverse transcriptase PCR analysis of TRPML1-3 messenger RNA expression in WT and NPC human fibroblasts, and NPC1−/− mouse macrophages. Expression levels were normalized to that of glyceraldehyde-3-phosphate dehydrogenase (human fibroblast) and L32 (mouse macrophage). For panels c and d, data are presented as the mean±s.e.m. (WT (blue), n=6; NPC (red), n=8). Statistical comparisons were made using analysis of variance: *P<0.05.