Figure 5. Full-Length Htt^exp Sensitizes InsP₃R1 to Activation by InsP₃.

(A) Microsomes from Sf9 cells coinfected with RT1 and Htt-23Q or Htt-82Q baculoviruses were solubilzed in 1% CHAPS, precipitated with anti-InsP₃R1 polyclonal antibodies, and blotted with the anti-Htt monoclonal antibodies. The input lanes contain 1/10 of lysates used in the immunoprecipitation experiments.

(B) Activity of InsP₃R1 coexpressed in Sf9 cells with Htt-23Q and reconstituted into planar lipid bilayers. Responses to application of 100 nM InsP₃ and 2 µM InsP₃ are shown. Each current trace corresponds to 10 s (2 s for expanded traces) of current recording from the same experiment.

(C) The average InsP₃R1 open probability (P_o) was calculated for a 5 s window of time and plotted for the duration of an experiment. The times of 100 nM and 2 µM InsP₃ additions to the bilayer are shown above the P_o plot. Data from the same experiment are shown on (B) and (C). Similar results were obtained in four independent experiments.

(D and E) Same as (B) and (C) for InsP₃R1 coexpressed in Sf9 cells with Htt-82Q. Similar results were obtained in six independent experiments.