Septin complex as a novel regulator of autophagosome biogenesis

Abstract

Eukaryotic cells achieve homeostasis inside the cells by maintaining the balance between synthesis and degradation of macromolecules. In particular, protein degradation is taken care of by two important systems viz. the Ubiquitin-Proteasome System (UPS) and Autophagy. Macroautophagy, herein autophagy is a major intracellular catabolic pathway that is indispensable for maintaining cellular homeostasis. This process is evolutionary conserved and is required not only for the degradation of unwanted and excess proteins but also for damaged organelles. In yeast, this process begins near vacuole called as pre-autophagosomal structure (PAS) at which a small membranous structure called as phagophore is formed. This phagophore then expands into double-membrane vesicles called autophagosomes that capture cytoplasmic cargoes and deliver them to vacuole or lysosomes for degradation. Based on the cargo that is captured, autophagy is divided into two types i.e. selective autophagy where a particular cargo such as peroxisomes (pexophagy), mitochondria (mitophagy) etc. are degraded while in general autophagy a portion of cytoplasm is degraded and thus the cargo is not specific (Johansen and Lamark 2011, Weidberg, et al. 2011).