Autophagy is a physiological process responsible for the degradation of cytoplasmic components within lysosomes. It involves the formation of double-membraned vesicles called autophagosomes that encapsulate cytoplasmic contents and deliver the cargo to the lysosome for destruction. It increases in response to cell stress such as deprivation of nutrients or growth factors. Autophagy plays a crucial role in turnover of long-lived, misfolded or aggregated proteins, damaged or redundant organelles, as well as in elimination of intracellular pathogens.
Although widely viewed as an essential process to maintain cellular homeostasis and functions, dysregulation in autophagy can have dire consequences. Its linkage to cancer, muscular and neurodegenerative diseases has generated a lot of interest in investigating autophagic pathways. Below we have discussed one of the main biomarkers used to monitor autophagy.
LC3B- An important Autophagy Biomarker
LC3B, a sub-unit of microtuble-associated protein LC3 (light chain 3), is one of the most reliable and widely used autophagy biomarkers. Along with other associated molecules, it helps guide and regulate autophagosome assembly and formation. After synthesis, LC3B is cleaved to expose a C-terminal glycine, representing the inactive cytosolic form LC3B-I.
During autophagy, the C-terminus covalently links to autophagosomal vesicle membranes and is called LC3B-II. The conversion of LC3B-I to LC3B-II is therefore usually associated with the formation of autophagosomes. As autophagosomes fuse with lysosomes to form autolysosomes, LC3B-II in the autolysosomal lumen gets degraded. This lysosomal turnover of the autophagosomal marker LC3B-II reflects starvation-induced autophagic activity.
Learn more about LC3 by following the link to this review.