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Abstract
Inhibition of phosphatidylcholine (PC) synthesis via the phosphatidylethanolamine (PE) methylation pathway was shown to decrease the secretion of VLDL from primary rat hepatocytes (Nishimaki-Mogami et al. 1996. Biochim. Biophys. Acta. 1304: 21–31). To understand further the role of PE methylation, we determined the effect of bezafibrate, an inhibitor of PE methylation, on VLDL assembly within the microsomal lumen. Bezafibrate was shown to decrease VLDL (triacylglycerol) secretion only when cellular PE methylation was active in the presence of methionine. Pulse-chase experiments showed that bezafibrate treatment did not impair the movement of [35S]apolipoprotein (apo)B-48 from microsomal membranes into the lumen. However, bezafibrate treatment resulted in reduced VLDL-[35S]apoB-48 and increased [35S]apoB-48-containing particles in the HDL density range (HDL-[35S]apoB-48) within the lumen. Inhibition of PE methylation by bezafibrate or 3-deazaadenosine after the completion of HDL-[35S]apoB-48 assembly effectively decreased VLDL-[35S]apoB-48 secretion with a concomitant increase in HDL-[35S]apoB-48 secretion.These findings suggest that inhibition of PC synthesis via the PE methylation pathway impairs the stage of bulk triacylglycerol incorporation during the assembly of VLDL.
Highlights
Inhibition of phosphatidylcholine (PC) synthesis via the phosphatidylethanolamine (PE) methylation pathway was shown to decrease the secretion of VLDL from primary rat hepatocytes
To further ascertain that bezafibrate decreases VLDL secretion only when the cellular PE methylation pathway is active, we examined the effect of methionine depletion on bezafibrate action
Decreased VLDL secretion by bezafibrate is dependent on cellular PE methylation activities In the previous study, we demonstrated that impaired VLDL secretion by bezafibrate or DZA is dependent on cellular PE methylation activities [10]
Summary
Inhibition of phosphatidylcholine (PC) synthesis via the phosphatidylethanolamine (PE) methylation pathway was shown to decrease the secretion of VLDL from primary rat hepatocytes Inhibition of PE methylation by bezafibrate or 3-deazaadenosine after the completion of HDL-[35S]apoB-48 assembly effectively decreased VLDL-[35S]apoB-48 secretion with a concomitant increase in HDL-[35S]apoB-48 secretion. These findings suggest that inhibition of PC synthesis via the PE methylation pathway impairs the stage of bulk triacylglycerol incorporation during the assembly of VLDL.—Nishimaki-Mogami, T., Z. We showed that inhibition of PC synthesis via the PE methylation pathway by bezafibrate or 3-deazaadenosine (DZA) decreases VLDL secretion from primary rat hepatocytes [10].
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