Sphingomyelin Regulates the Activity of Secretory Phospholipase A₂ in the Plasma Membrane

Abstract

We examined the effect of the cellular sphingolipid level on the release of arachidonic acid (AA) and the activity of secretory phospholipase A2 (sPLA2 ) using two Chinese hamster ovary (CHO)-K1 cell mutants, LY-B and LY-A cells, deficient in sphingolipid synthesis. In LY-B cells, deficiency of sphingolipids enhanced the release of AA induced by bee venom sPLA2-III or human sPLA2-V. These alterations were reversed by replenishment of exogenous sphingomyelin (SM). In LY-A cells, deficiency of SM increased the release of AA induced by sPLA2. In CHO-K1 cells, decrease and increase of SM level in the plasma membrane by pharmacological methods increased and inhibited the release of AA, respectively. SM inhibited the activity of sPLA2 in vitro. Niemann-Pick disease type C (NPC) is a lysosomal storage disorder caused by mutation of either the NPC1 or NPC2 gene, and is characterized by accumulation of cholesterol and sphingolipids including SM in late endosomes/lysosomes. Increased levels of AA and sPLA2 activity are involved in various neurodegenerative diseases. In CHO cells lacking NPC1 (A101 cells), SM level was lower in the plasma membrane, while it was higher in late endosomes/lysosomes. The release of AA induced by sPLA2 was increased in A101 cells than that in parental cells (JP17 cells), which was attenuated by adding exogenous SM. In addition, sPLA2 -III-induced cytotoxicity in A101 cells was much higher than that in JP17 cells. These results suggest that SM in the plasma membrane plays important roles in regulating sPLA2 activity and the enzyme-induced cytotoxicity in A101 cells.

Defective cortex glia plasma membrane structure underlies light-induced epilepsy in cpes mutants

“…6 A and B ). SM has been shown to negatively regulate phospholipases (cPLA2 and sPLA2) in the plasma membrane ( 32 , 33 ). We wondered whether the plasma membrane in cpes mutants is increasingly damaged due to activation of phospholipases.…”

CHO/LY‐B cell growth under limiting sphingolipid supply: Correlation between lipid composition and biophysical properties of sphingolipid‐restricted cell membranes

“…LY-B cells have been used in multiple studies exploring SL effects, and their interaction with glycerophospholipid metabolism. [32][33][34][35] SM synthases, which use Cer and phosphatidylcholine as substrates to produce SM and diacylglyceride, are used in the de novo synthesis pathway, sometimes also involved in reutilization of ceramide 30,36 from exogenous or endogenous sources. In a previous work, 37 plasma membrane (PM) preparations from CHO cells and model membranes prepared from their lipid extracts had been characterized.…”

“…Mutant LY‐B and wild‐type CHO cells could be comparatively studied to determine the effect of SL depletion on the biophysical properties of cell membranes. LY‐B cells have been used in multiple studies exploring SL effects, and their interaction with glycerophospholipid metabolism 32‐35 . SM synthases, which use Cer and phosphatidylcholine as substrates to produce SM and diacylglyceride, are used in the de novo synthesis pathway, sometimes also involved in reutilization of ceramide 30,36 from exogenous or endogenous sources.…”

CHO/LY-B cell growth under limiting sphingolipid supply: correlation between lipid composition and biophysical properties of sphingolipid-restricted cell membranes+

“…Mutant LY-B and wild type CHO cells could be comparatively studied to determine the effect of SL depletion on the biophysical properties of cell membranes. LY-B cells have been used in multiple studies exploring SL effects, and their interaction with glycerophospholipid metabolism [32][33][34][35] .…”