Autophagy: fasting to be healthy
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Date
2018
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جامعة الشيخ عبدالله البدري
Abstract
Autophagy is an intracellular degradation system that delivers cytoplasmic constituents to the
lysosome. Despite its simplicity, recent progress has demonstrated that autophagy plays a wide
variety of physiological and pathophysiological roles, which are sometimes complex. Autophagy
consists of several sequential steps²sequestration, transport to lysosomes, degradation, and
utilization of degradation products²and each step may exert different function.
This process is quite distinct from endocytosis-mediated lysosomal degradation of extracellular
and plasma membrane proteins. There are three types of autophagy²macroautophagy,
microautophagy, and chaperone-mediated autophagy²and the term ³autophagy´ usually
indicates macroautophagy unless otherwise specified.
Autophagy is mediated by a unique organelle called the autophagosome. As autophagosomes
engulf a portion of cytoplasm, autophagy is generally thought to be a nonselective degradation
system. This feature is in marked contrast to the ubiquitin±proteasome system, which specifically
recognizes only ubiquitinated proteins for proteasomal degradation. It is therefore reasonable to
assume that the ubiquitin±proteasome system has numerous specific functions because it can
selectively degrade thousands of substrates.