Figure 4. Stoichiometric analyses of TRPML3/TRPV5 currents.

(A–D) Traces show currents at −150 mV recorded from HEK293 cells expressing TRPV5/TRPML3, in the presence of extracellular solutions containing 140 mM Na⁺ (condition 1, black), 150 mM K⁺ (condition 2, red), 140 mM Na⁺, 0.1 mM EGTA (condition 3, blue), and 150 mM K⁺, 0.1 mM EGTA (condition 4, pink). We hypothesized that the current recorded under condition 1 represents the novel conductance, the current under condition 2 consists of the novel conductance and TRPML3, the current under condition 3 is composed of the novel conductance and TRPV5, and finally, under condition 4, we expected that the recorded current consists of all three conductances. (E–F) Subtraction of A from B (in E) which represents pure TRPML3; subtraction of A from C (in F) which results in pure TRPV5. (G–I) HEK293 cells were transfected with TRPML3 and TRPV5 expression plasmids either pure (0% and 100%) and at molar ratios 1∶10 (10%), 1∶5 (20%), 2∶3 (40%), 1∶1 (50%), 3∶2 (60%), 5∶1 (80%) and 10∶1 (90%), respectively. Currents were elicited at −150 mV under conditions 1–3 and individual conductances for TRPML3 and TRPV5 were extracted as described in (E–F). Shown is the average fraction of novel current (G, black circles), TRPML3 (H, red triangles), and TRPV5 (I, blue triangles) is plotted against the fraction of TRPML3 over TRPV5 (G,H) and TRPV5 over TRPML3 (I) (n = 5–11).