Accumulation and aggregation of disease-causing proteins is a hallmark of several neurodegenerative disorders such as Parkinson's, Alzheimer's and Huntington's disease. One of the main goals of research in neurodegenerative disorders has been to improve clearance of these accumulated proteins by selectively activating degradation machinery such as autophagy. Current approaches to modulate autophagy result in global and non-specific activation of autophagic and other cellular pathways. Using an example of Huntington's disease, we reported that selective clearance can be achieved by posttranslational modification of the mutant htt by acetylation at lysine residue 444 (K444). Increased acetylation at K444 facilitates trafficking of mutant Htt into autophagosomes, significantly improves clearance of the mutant protein by macroautophagy and reverses the toxic effects of mutant huntingtin in vitro and in vivo. These preliminary studies suggest a critical role for acetylation in the control of regulated clearance of mutant huntingtin. Here we propose to examine the molecular pathways of such acetylation-mediated clearance of mutant htt. In Aim1 we propose to validate the role of mutant htt acetylation in vivo by generating a knockin mouse model expressing acetylation-resistant full-length mutant htt to perform biochemical, neuropathological and behavioral studies. Aim 2 will examine the interactions of autophagy machinery with acetylated mutant huntingtin. The cargo recognition process of proteins destined for the autophagosome is not well understood. We propose to assess interactions of acetyl-htt with the autophagy machinery, specifically the proteins involved in shuttling protein cargo to the autophagosome. In Aim 3 we will examine the role of HDAC inhibitors in promoting clearance of mutant huntingtin. Using cellular models systems, we will examine the relative contribution of various HDACs to clearance of acetylated mutant Htt. In summary, the proposed study will examine how cells regulate mutant Htt levels, a critical risk factor for HD. Identifying the mechanisms that control mutant Htt levels could lead to novel therapeutic strategies by directly targeting mutant Htt. Understanding the molecular mechanisms involved in the recognition and selective autophagic clearance of mutant Htt may facilitate studies of other disease-causing proteins that accumulate in various neurodegenerative disorders.