Sphingomyelin synthases 1 and 2 exhibit phosphatidylcholine phospholipase C activity

Abstract

Many studies have confirmed the enzymatic activity of a mammalian phosphatidylcholine (PC) phospholipase C (PLC) (PC-PLC), which produces diacylglycerol (DAG) and phosphocholine through the hydrolysis of PC in the absence of ceramide. However, the protein(s) responsible for this activity have never yet been identified. Based on the fact that tricyclodecan-9-yl-potassium xanthate can inhibit both PC-PLC and sphingomyelin synthase (SMS) activities, and SMS1 and SMS2 have a conserved catalytic domain that could mediate a nucleophilic attack on the phosphodiester bond of PC, we hypothesized that both SMS1 and SMS2 might have PC-PLC activity. In the present study, we found that purified recombinant SMS1 and SMS2 but not SMS-related protein have PC-PLC activity. Moreover, we prepared liver-specific Sms1 /global Sms2 double-KO mice. We found that liver PC-PLC activity was significantly reduced and steady-state levels of PC and DAG in the liver were regulated by the deficiency, in comparison with control mice. Using adenovirus, we expressed Sms 1 and Sms 2 genes in the liver of the double-KO mice, respectively, and found that expressed SMS1 and SMS2 can hydrolyze PC to produce DAG and phosphocholine. Thus, SMS1 and SMS2 exhibit PC-PLC activity in vitro and in vivo .

Sphingomyelin synthase–related protein SMSr is a phosphatidylethanolamine phospholipase C that promotes nonalcoholic fatty liver disease

“…Next, we utilized the dKO and the tKO mice on chow diet to perform the rest of the experiments. We measured different lipid levels in the liver of the dKO and the tKO mice and confirmed that there were no differences in sphingomyelin and ceramide ( 9 ) ( Fig. S5 ).…”

“…We and others found that SMSr has PLC activity ( 6 , 8 ) and specifically hydrolyzes PE, making it a phosphatidylethanolamine PLC (PE-PLC) ( 6 ). We also found that SMS1 and SMS2 are two phosphatidylcholine (PC)-PLCs ( 9 ). Given the fact that ( 10 , 11 , 12 , 13 ) PC-PLC and phosphatidylinositol (PI)-PLCs ( 14 ) maintain PC and PI levels and regulate many important biological functions, SMSr-mediated PE-PLC activity should have an important biological function.…”

“…Then, we crossed Sms1 -Flox/ Sms2 -KO mice with global Smsr -KO mice to yield Sms1 -Flox/ Sms2 / Smsr -KO mice. Finally, we crossed Sms1 -Flox/ Sms2 -KO mice and Sms1 -Flox/ Sms2 / Smsr -KO mice with albumin-Cre transgenic mice, respectively, to obtain liver-specific Sms1 /global Sms2 -dKO mice ( 73 ) and liver-specific Sms1 -KO/global Sms2/ global Smsr -tKO mice ( 6 , 9 ). We used male and female mice that had a C57BL/6 genetic background.…”

Evaluation of Lipidomics Profile of Quinoa Flour and Changes during Storage Based on Ultra Performance Liquid Chromatography Coupled with Quadrupole Exactive Orbitrap Mass Spectrometry

“…During the storage of quinoa, major lipids involved in the glycerophospholipid pathway include PE, PI, PS, and PG. DG could be involved in the synthesis of PE and PC as a lipid anchor in the presence of the corresponding phosphotransferases, while phospholipase C catalyzes the hydrolysis of PC and PE for the synthesis of DG [40]. In addition, lysophospholipid (LPC and LPE) could be generated via the cleavage of glycerophospholipid (PC and PE) molecules by phospholipase A1 or phospholipase A2, whereas lysophospholipid and acyl-coenzyme A could form glycerophospholipid in the presence of lysophospholipid acyltransferase.…”

Phosphatidylcholine-Specific Phospholipase C as a Promising Drug Target

“…Most notably, the genetic sequence of the mammalian PC-PLC has not yet been unambiguously identified. Recently, sphingomyelin synthases 1 and 2 were shown to exhibit PC-PLC-like activity [3], and are required for sphingomyelin homeostasis and growth in human HeLa cancer cells [4]. Thus, it is plausible that other enzymes could mimic PC-PLC activity (moonlighting function).…”