(B) Effect of TBK1 on HTT in the cellular HD model. TBK1 and TBK1 Δ690-713 both phosphorylate monomeric or soluble HTTex1 72Q at S13 residue leading the reduction of the aggregation, but TBK1 also reduces the aggregation of both HTTex1 and HTTex1 S13A/S16A through the lowering of the HTT levels at the monomeric stage by enhancing the autophagic degradation. TBK1 Δ690-713 only reduces the aggregation of phosphorylation-competent HTTex1 but does not reduces the aggregation of HTTex1 S13A/S16A highlighting the role of S13 phosphorylation in aggregation inhibition. 