The normal growth and development of eukaryotic cells requires a constant balance between biosynthetic and degradative processes. There are two highly conserved mechanisms for degradation in eukaryotes that are responsible for the majority of protein turnover: one is the ubiquitin-proteasome system and the other is autophagy. Under conditions of normal growth, the bulk of protein degradation occurs via the proteasomal machinery (reviewed in 1). Proteins that are to be degraded are post-translationally tagged with poly-ubiquitin and are subsequently broken down via the multi-subunit 26S proteasome present in the cytosol and nucleus. In contrast, autophagy is largely a non-specific process that leads to the vacuolar/lysosomal degradation of not just proteins, but also of other cytosolic macromolecular components. Importantly, autophagy is the only degradative pathway that has the capacity to degrade large aggregates and even entire organelles. Autophagy plays a role in normal development and differentiation; however, it is also involved in defense against pathogens, life span extension, and the prevention of certain types of cancer and neurodegeneration (reviewed in 2).

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Journal Article | Research Support, N.I.H., Extramural | Review

Authors

Nair U, Klionsky DJ

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