Regulated secretion of acid sphingomyelinase: implications for selectivity of ceramide formation.

Abstract

The acid sphingomyelinase (aSMase) gene gives rise to two distinct enzymes, lysosomal sphingomyelinase (L-SMase) and secretory sphingomyelinase (S-SMase), via differential trafficking of a common protein precursor. However, the regulation of S-SMase and its role in cytokine-induced ceramide formation remain ill defined. To determine the role of S-SMase in cellular sphingolipid metabolism, MCF7 breast carcinoma cells stably transfected with V5-aSMase(WT) were treated with inflammatory cytokines. Interleukin-1β and tumor necrosis factor-α induced a time- and dose-dependent increase in S-SMase secretion and activity, coincident with selective elevations in cellular C(16)-ceramide. To establish a role for S-SMase, we utilized a mutant of aSMase (S508A) that is shown to retain L-SMase activity, but is defective in secretion. MCF7 expressing V5-aSMase(WT) exhibited increased S-SMase and L-SMase activity, as well as elevated cellular levels of specific long-chain and very long-chain ceramide species relative to vector control MCF7. Interestingly, elevated levels of only certain very long-chain ceramides were evident in V5-aSMase(S508A) MCF7. Secretion of the S508A mutant was also defective in response to IL-1β, as was the regulated generation of C(16)-ceramide. Taken together, these data support a crucial role for Ser(508) in the regulation of S-SMase secretion, and they suggest distinct metabolic roles for S-SMase and L-SMase.

• Authors: Russell W Jenkins, Daniel Canals, Jolanta Idkowiak-Baldys, Fabio Simbari, Patrick Roddy, David M Perry, Kazuyuki Kitatani, Chiara Luberto, Yusuf A Hannun
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 285 Issue 46 Pg. 35706-18 (Nov 12 2010) ISSN: 1083-351X [Electronic] United States
• PMID: 20807762 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Ceramides
• Interleukin-1beta
• Tumor Necrosis Factor-alpha
• Serine
• SMPD1 protein, human
• Sphingomyelin Phosphodiesterase

Topics

• Amino Acid Substitution
• Blotting, Western
• Cell Line, Tumor
• Ceramides (metabolism)
• Dose-Response Relationship, Drug
• Extracellular Space (drug effects, enzymology)
• HEK293 Cells
• Humans
• Interleukin-1beta (pharmacology)
• Intracellular Space (drug effects, enzymology)
• Lysosomes (enzymology)
• Mutation
• Reverse Transcriptase Polymerase Chain Reaction
• Serine (genetics, metabolism)
• Sphingomyelin Phosphodiesterase (genetics, metabolism)
• Time Factors
• Transfection
• Tumor Necrosis Factor-alpha (pharmacology)