Lysophospholipase

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Introductions

Lysophospholipases are commonly referred to as neuropathy target esterase (NTE) and NTE-associated esterase, respectively. NTE was discovered during the study of organophosphate induced delayed neuropathy. It is a transmembrane protein in the endoplasmic reticulum with phospholipase B activity, catalyzes the deacylation of lecithin and lysolecithin, regulates cellular phospholipid metabolism, and is essential for embryonic development, neurodevelopment, and axonal maintenance.

Structure

Lysophospholipases are expressed exogenously and endogenously as a membrane-integrated protein on the endoplasmic reticulum. The remaining structures (including the regulatory and catalytic domains) are located on the cytoplasmic side of the endoplasmic reticulum, with the C-terminus facing the cytoplasmic side of the endoplasmic reticulum and the catalytic domain attached to the cytoplasmic side of the endoplasmic reticulum. In vitro assay showed that PNPLA7 has the catalytic activity of lysophosphatidylcholine (LPC), which can hydrolyze lysophosphatidylcholine and other lysophospholipids.

Figure 1. Structure of Lysophospholipases. (Chang P A., at al. 2010)

Expression

The expression of lysophospholipases is regulated by nutritional status and is relatively abundant in adipose tissue, skeletal muscle, cardiac muscle and testis where lipid metabolism is active. As a lysophospholipase highly expressed in adipose tissues, the expression of Lysophospholipases is regulated by nutritional status. The expression of lysophospholipases was relatively low in all tissues of mice under feeding condition, which enhanced the expression of lysophospholipases in adipose tissue, cardiac muscle, skeletal muscle, testis and liver; and feeding after starvation decreased the expression of lysophospholipases. Quantitative PCR analysis revealed that fasting regulated the transcriptional splicing of lysophospholipases, increasing the expression of active lysophospholipases and decreasing the expression of inactive splice mutants. The expression of lysophospholipases was significantly increased in the liver of mice fed a high-fat diet compared to mice fed a normal diet.

Lysophospholipases regulate hepatic lipid metabolism and fatty liver

The tissue distribution, catalytic activity, cellular localization and expression characteristics of lysophospholipases suggest that they may play a role in lipid metabolism and energy metabolism. Stable expression of mouse lysophospholipases in COS-7 cells significantly reduced the intracellular content of LPC containing unsaturated fatty acids without altering the levels of other lysophospholipids. In addition, expression of lysophospholipases in hepatocellular carcinoma cells Huh7 significantly reduced lipid accumulation and knocked down the expression of lysophospholipases.

Summary

As a lysophospholipase in the endoplasmic reticulum membrane, lysophospholipases hydrolyze lysophospholipids and regulate phospholipid metabolism, but the physiological role of lysophospholipases-mediated phospholipid metabolism is not fully understood. lysophospholipases are mainly expressed in adipose tissue, cardiac muscle, skeletal muscle and other tissues with active lipid metabolism and energy conversion. The expression of lysophospholipases is regulated by nutritional status. It was found that lysophospholipases in the liver regulate the degradation of ApoE via the ubiquitin-proteasome pathway and affect the secretion of VLDL, thus regulating hepatic lipid metabolism, and the interaction between lysophospholipases and ApoE is not related to their catalytic activity.