Why LC3B Antibodies Make Ideal Autophagosomes Membrane Markers

The human form of microtubule-associated protein light chain 3 (LC3) is expressed as 3 splice variants LC3A, LC3B, and LC3C.¹ LC3B is a subunit of the MAP1A and MAP1B microtubule-binding proteins and plays a central role in autophagosome membrane structure. This ubiquitin-like modifier is known to be involved in early stages of autophagosome formation and specifically with phagophore membrane elongation. LC3B also interacts with autophagy receptors such as p62/SQSTM1 and NBR1 during substrate selection for autophagic degradation.²

Researchers using LC3B knock out mice to determine if LC3 is required for autophagy found that the mice do develop normally, likely due to a compensatory autophagy mechanism by other members of the MAP1LC3 subfamily.³

During early stages of autophagosome formation, the cytosolic form of LC3, known as LC3-I, becomes conjugated to the head of a lipid via a series of ubiquitin-like reactions. This lipid modified form of LC3, known as LC3-II, is then believed to be recruited for autophagosome membrane expansion and fusion. Detecting the conversion of LC3-I (~19 kDa) to LC3-II (~17 kDa) is considered a useful, if not definitive⁴, autophagy marker in mammalian cells. Unlike LC3A and LC3C however, LC3B does not undergo C-terminal cleavage and exists in a single modified form with an essential site for post-translation modification at Lys-122 rather than the conserved Gly-120 of the other two variants.¹

Antibodies to all three LC3 splice variants are widely used as markers of autophagosomes. For example, our LC3B/MAP1LC3B Antibody [NB100-2220] has been cited for use as an autophagosome marker in over 1300 published research articles in a wide variety of applications. In one study, researchers used Bio-Techne's LC3B Antibodies [NB100-2220] and [NB600-1384] and recombinant proteins LC3A and LC3B to determine the distinct sub-cellular expression patterns of LC3B.⁵ In another study, the LC3B antibody [NB100-2220] was used to monitor autophagy during exercise and insulin stimulation in skeletal muscle.⁶

In many studies, researchers have used Bio-Techne's fluorescent conjugated LC3B/MAP1LC3B antibodies for autophagosome labeling in immunofluorescence and flow cytometry applications. For instance, researchers used the DyLight-conjugated LC3B antibody [NB100-2220G] to report a link between AKT mediated glycolytic metabolism and autophagy.⁷ Additionally, our AlexaFlour-conjugated LC3B antibody [NB100-2220AF488] on cultured monocytes to label autophagosomes.⁸