Studies on the role of acid sphingomyelinase and ceramide in the regulation of tumor necrosis factor α (TNFα)-converting enzyme activity and TNFα secretion in macrophages

Krasimira A. Rozenova, Gergana M. Deevska, Alexander A. Karakashian, Mariana N. Nikolova-Karakashian

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Acid sphingomyelinase (ASMase) has been proposed to mediate lipopolysaccharide (LPS) signaling in various cell types. This study shows that ASMase is a negative regulator of LPS-induced tumor necrosis factor α (TNFα) secretion in macrophages. ASMase-deficient (asm-/-) mice and isolated peritoneal macrophages produce severalfold more TNFα than their wild-type (asm+/+) counterparts when stimulated with LPS, whereas the addition of exogenous ceramides or sphingomyelinase reduces the differences. The underlying mechanism for these effects is not transcriptional but post-translational. The TNFα-converting enzyme (TACE) catalyzes the maturation of the 26-kDa precursor (pro-TNFα) to an active 17-kDa form (soluble (s)TNFα). In mouse peritoneal macrophages, the activity of TACE was the rate-limiting factor regulating TNFα production. A substantial portion of the translated pro-TNFα was not processed to sTNFα; instead, it was rapidly internalized and degraded in the lysosomes.TACEactivity was 2-3-fold higher in asm-/- macrophages as compared with asm +/+ macrophages and was suppressed when cells were treated with exogenous ceramide and sphingomyelinase. Indirect immunofluorescence analyses revealed distinct TNFα-positive structures in the close vicinity of the plasma membrane in asm-/- but not in asm+/+ macrophages. asm-/- cells also had a higher number of early endosomal antigen 1-positive early endosomes. Experiments that involved inhibitors of TACE, endocytosis, and lysosomal proteolysis suggest that in the asm-/- cells a significant portion of pro-TNFα was sequestered within the early endosomes, and instead of undergoing lysosomal proteolysis, it was recycled to the plasma membrane and processed to sTNFα.

Original languageEnglish
Pages (from-to)21103-21113
Number of pages11
JournalJournal of Biological Chemistry
Volume285
Issue number27
DOIs
StatePublished - Jul 2 2010

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Fingerprint

Dive into the research topics of 'Studies on the role of acid sphingomyelinase and ceramide in the regulation of tumor necrosis factor α (TNFα)-converting enzyme activity and TNFα secretion in macrophages'. Together they form a unique fingerprint.

Cite this