Huntingtin interacts with dynein and TrkB. A, Coimmunoprecipitation of HTT with TrkB from HEK cells transfected with TrkB and HTTN-1301–17Q or HTTN-1301–73Q show no interaction differences upon polyQ expansion in HTT. B, Immunoprecipitation of TrkB from HEK cells transfected with TrkB and dynein IC-1B or IC-2C reveals a preferential interaction of TrkB with dynein IC-1B compared with dynein IC-2C. C, HEK cells were transfected with TrkB, dynein IC-1B, and HTTN-1301–17Q or HTTN-1301–73Q. Anti-TrkB or dynein antibodies specifically coimmunoprecipitate wild-type and mutant HTT with the same efficacy. D, Trk or dynein immunoprecipitations were performed from Hdh+/+ and HdhQ111/Q111 mouse brain extracts. HD mutation does not affect HTT coimmunoprecipitation.