The Lipid-Modifying Enzyme SMPDL3B Negatively Regulates Innate Immunity, 2015, Heinz et al.

The Lipid-Modifying Enzyme SMPDL3B Negatively Regulates Innate Immunity
Heinz; Baumann; Köberlin; Snijder; Gawish; Shui; Sharif; Aspalter; Müller; Kandasamy; Breitwieser; Pichlmair; Bruckner; Rebsamen; Blüml; Karonitsch; Fauster; Colinge; Bennett; Knapp; Superti-Furga

Lipid metabolism and receptor-mediated signaling are highly intertwined processes that cooperate to fulfill cellular functions and safeguard cellular homeostasis. Activation of Toll-like receptors (TLRs) leads to a complex cellular response, orchestrating a diverse range of inflammatory events that need to be tightly controlled.

Here, we identified the GPI-anchored Sphingomyelin Phosphodiesterase, Acid-Like 3B (SMPDL3B) in a mass spectrometry screening campaign for membrane proteins co-purifying with TLRs. Deficiency of Smpdl3b in macrophages enhanced responsiveness to TLR stimulation and profoundly changed the cellular lipid composition and membrane fluidity. Increased cellular responses could be reverted by re-introducing affected ceramides, functionally linking membrane lipid composition and innate immune signaling. Finally, Smpdl3b-deficient mice displayed an intensified inflammatory response in TLR-dependent peritonitis models, establishing its negative regulatory role in vivo.

Taken together, our results identify the membrane-modulating enzyme SMPDL3B as a negative regulator of TLR signaling that functions at the interface of membrane biology and innate immunity.

Link | PDF (Cell Reports)

 

Relates to findings presented in IIMEC15 - Alain Moreau.

Mouse study. Highlights —

• Identification of SMPDL3B as lipid-modulating phosphodiesterase on macrophages
• SMPDL3B as negative regulator of Toll-like receptor function. Smpdl3b-deficiency strongly affected macrophage lipid composition and fluidity and led to higher responsiveness to TLR stimulation
• Negative regulatory role for SMPDL3B in Toll-like receptor function
• Strong influence of SMPDL3B on membrane lipid composition and fluidity

 

Quotes from introduction —