Proteostasis integrates biological pathways controlling biogenesis, trafficking, folding, and degradation of proteins. This book focuses on two protein breakdown/degradation processes (proteolysis), which are part of a normally functioning proteostatic system: the ubiquitin-proteasome system and autophagy.Chapter 2 of this book is freely available as a downloadable Open Access PDF at http: //www.taylorfrancis.com under a Creative Commons Attribution-Non Commercial-No Derivatives (CC-BY-NC-ND) 4.0 license.