(C) Representative western blot of HTT (ab-MAB2166) and HTT pS13 (ab-CHDI-90001039-1) upon coexpression of HTT N543 55Q with the indicated kinase for 24 hour in HEK293T cells. (D) Quantification of HTT pS13 using the Singulex assay (using ab-MW1 as capture and CHDI-90001039 or 2B7 as detection antibodies for pS13 or total HTT) upon coexpression of HTT N543 55Q with the indicated kinase for 24 hour in HEK293T cells from the experiment in C (representative of 3 repeats). 