Interaction of ceramides, sphingosine, and sphingosine 1-phosphate in regulating DNA synthesis and phospholipase D activity.
C2- and C6-ceramides (N-acetylsphingosine and N-hexanoylsphingosine, respectively) abolished the stimulation of DNA synthesis by sphingosine 1-phosphate in rat fibroblasts. This inhibition by ceramide was partially prevented by insulin. C2-ceramide did not alter the stimulation of DNA synthesis by insulin and decreased the sphingosine-induced stimulation by only 16%. The ceramides did not significantly modify the actions of sphingosine or sphingosine 1-phosphate in decreasing cAMP concentrations. C2- and C6-ceramides blocked the activation of phospholipase D by sphingosine 1-phosphate, and this inhibition was not affected by insulin. Okadaic acid decreased the activation of phospholipase D by sphingosine 1-phosphate and did not reverse the inhibitory effect of C2-ceramide on this activation. Therefore, this effect of C2-ceramide is unlikely to involve the stimulation of phosphoprotein phosphatase activity. Sphingosine did not activate phospholipase D activity significantly after 10 min. C2-ceramide stimulated the conversion of exogenous [3H]sphingosine 1-phosphate to sphingosine and ceramide in fibroblasts. Ceramides can inhibit some effects of sphingosine 1-phosphate by stimulating its degradation via a phosphohydrolase that also hydrolyzes phosphatidate. Furthermore, C2- and C6-ceramides stimulated ceramide production from endogenous lipids, and this could propagate the intracellular signal. This work demonstrates that controlling the production of ceramide versus sphingosine and sphingosine 1-phosphate after sphingomyelinase activation could have profound effects on signal transduction.
Gómez-Muñoz
A
A
Department of Biochemistry, University of Alberta, Edmonton, Canada.
Waggoner
D W
DW
O'Brien
L
L
Brindley
D N
DN
D000818:Animals; D002460:Cell Line; D002518:Ceramides / Q000378:metabolism* / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004988:Ethers, Cyclic / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D008246:Lysophospholipids; D019319:Okadaic Acid; D010739:Phospholipase D / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D013329:Structure-Activity Relationship
D002518:Ceramides; D004791:Enzyme Inhibitors; D004988:Ethers, Cyclic; D007328:Insulin; D008246:Lysophospholipids; D019319:Okadaic Acid; C060506:sphingosine 1-phosphate; D004247:DNA; D010739:Phospholipase D; D013110:Sphingosine