New progress has been made in the study of leucine-regulated autophagy

Recently, the research results of Professor Yan Xianghua's team from the National Key Laboratory of Agricultural Microbiology, Hubei Hongshan Laboratory and the Frontier Science Center for Animal Breeding and Healthy Breeding of Huazhong Agricultural University were published in Cell Reports with the title "Lysine crotonylation regulates leucine-deprivation-induced autophagy by a 14-3-3ε-PPM1B axis".
Studies have revealed the molecular mechanism
by which leucine regulates the initiation process of autophagy through lysine crotonylation modification pathway.

One of the important prerequisites for precision pig feeding is to analyze as much as possible the biochemical metabolic pathways and nutritional physiological functions
of nutrients in the process of digestion, absorption and metabolism in the body.
As one of the essential amino acids in pigs, one of the main functions of leucine is to participate in protein synthesis as a substrate, and in recent years, it has also been found that it can participate in the nutrient metabolism process
as a signaling molecule.
When the body is in a state of stress such as leucine starvation and nutrient deficiency, the autophagy process will be activated, the autophagosome wraps the substrate to be degraded and fuses with the lysosome, the content is degraded under the action of lysosomal hydrolase, and the small molecule nutrients produced by degradation will be absorbed and utilized by the body again to meet the nutritional needs under stress conditions and maintain the body's homeostasis
.
The leucine starvation-induced autophagy process is tightly regulated by a variety of protein post-translational modifications, although it is unclear
whether novel forms of post-translational modifications are involved.

The researchers first identified that lysine crotonylation modification was significantly upregulated during leucine starvation, and the level of crotonylation modification in animal liver increased
significantly after one week of feeding leucine starvation diet.
NaCr treatment, a crotonylation modification activator, increases crotonylation modification and activates the autophagy
process.
Therefore, this result suggests that crotonylation modifications are positively correlated with autophagy levels in vitro or in vivo
.

Next, the researchers identified a series of leucine-regulated crotonylated modified proteins
through lysine crotonylation modified proteomics.
Through bioinformatics data and validation tests, it was further found that the K73 and K78 crotonylation modifications of 14-3-3ε protein may play an important role
in leucine starvation-induced autophagy.
The 14-3-3ε protein crotonylation deletion mutations K73R and K78R can significantly inhibit the occurrence
of autophagy.
Through the molecular dynamics simulation test of 14-3-3ε protein crotonylation modification, K73 and K78 crotonylation modification can significantly increase the conformational instability of protein molecules, and make the secondary structure of protein molecules in a disordered state
.

Finally, the researchers identified PPM1B protein as a downstream effector molecule of 14-3-3ε protein, the interaction of this protein with 14-3-3ε protein disappeared after leucine starvation treatment, the interaction between PPM1B and 14-3-3ε was regulated by HDAC7-regulated crotonylation modification, and PPM1B was a phosphatase
of the autophagy initiation factor ULK1 。 In summary, this study reveals that leucine deficiency first inhibits HDAC7 activity, upregulates the level of crotonylation modification of 14-3-3ε protein, promotes the dissociation of PPM1B protein, and releases PPM1B dephosphorylation ULK1, thereby activating the molecular mechanism of autophagy initiation process, which provides a theoretical basis
for the design of pig precision feed formulation.