Extended Data Figure 4. Heterologous PKD1-L1 and PKD2-L1 form an ion channel.

(a) Immunoprecipitation of Flag– and HA–tagged PKD1-L1 and PKD2-L1 heterologously expressed in HEK293T cells. (b) Box (± SEM) and whisker (± SD) plots of the current densities measured from PKDx-L1 family-transfected HEK cells at -100 mV (bottom) and +100 mV (top). Averages are indicated by the red lines. Statistical significance from Student's t-test comparing transfected to untransfected cells are indicated by asterisks (P-value < 0.005; n = 10-23 cells) and those comparing PKD2-L1 to the pore mutants are indicated by double asterisks (* denotes P-value < 0.005 compared to untransfected cells; ** denotes P-value < 0.005 compared to PKD 1-L1/2-L1 transfected cells; n= 9-11 cells). (c) An alignment of the PKD2-L1 and PKD2 (polycystin 2) pore helix and selectivity filter with glutamate residues D523, D525, and D530 indicated. (d) Table listing the average reversal potential change relative to the standard Na⁺-based extracellular solution (average खE_rev) and the estimated relative permeability (P_x/P_Na) for HEK cells transfected with PKD2-L1 alone or with PKD2-L1 and PKD1-L1 (± SEM, n= 4-6 cells).