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Functional dichotomy of neutral and acidic sphingomyelinases in tumor necrosis factor signaling

K Wiegmann1, S Schütze, T Machleidt

  • 1Institut für Medizinische Mikrobiologie und Hygiene, Technische Universität München, Federal Republic of Germany.

Cell
|September 23, 1994
PubMed

Insights

Tumor necrosis factor (TNF) activates two types of sphingomyelinases (SMases) independently. These enzymes generate ceramide, controlling distinct signaling pathways like NF-kappa B activation and protein kinase signaling.

Area of Science:

  • Cellular Biology
  • Molecular Signaling
  • Biochemistry

Background:

  • Ceramide acts as a crucial second messenger in growth factor receptor signaling pathways.
  • Sphingomyelinases (SMases) are enzymes responsible for ceramide production.
  • Tumor necrosis factor (TNF) receptor signaling involves complex downstream events.

Purpose of the Study:

  • To investigate the distinct roles of neutral (N-)SMase and acidic (A-)SMase in TNF receptor signaling.
  • To elucidate the specific signaling pathways regulated by ceramide generated from different SMase types.
  • To determine if crosstalk exists between N-SMase and A-SMase mediated pathways.

Main Methods:

  • Activation of TNF receptor 55 (TNF-R55) to stimulate SMase activity.
  • Differentiating ceramide production by membrane-associated N-SMase and endosomal A-SMase.
  • Assessing downstream signaling events, including protein kinase activation, phospholipase A2, and NF-kappa B activation.

Main Results:

  • TNF receptor binding rapidly activates both N-SMase and A-SMase through distinct receptor domains.
  • N-SMase activation leads to ceramide generation that triggers proline-directed protein kinase(s) and phospholipase A2.
  • A-SMase activation results in ceramide generation that specifically activates NF-kappa B.
  • No cross-talk was observed between the N-SMase and A-SMase signaling pathways.

Conclusions:

  • N-SMase and A-SMase are independently activated by TNF receptor signaling.
  • Ceramide's downstream effects are dependent on its site of production (topology).
  • These two SMase pathways control distinct and non-overlapping aspects of TNF receptor signal transduction.

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