Clec12a inhibits MSU-induced immune activation through lipid raft expulsion
Ying Xu1, Dingka Song1,2, Wei Wang3
1Institute for Immunology, School of Medicine, Tsinghua University, Beijing, China.
Abstract:
Monosodium uric acid (MSU) crystal, the etiological agent of gout, has been shown to trigger innate immune responses via multiple pathways. It is known that MSU-induced lipid sorting on plasma membrane promotes the phosphorylation of Syk and eventually leads to the activation of phagocytes. However, whether this membrane lipid-centric mechanism is regulated by other processes is unclear. Previous studies showed that Clec12a, a member of the C-type lectin receptor family, is reported to recognize MSU and suppresses this crystalline structure-induced immune activation. How this scenario is integrated into the lipid sorting-mediated inflammatory responses by MSU, and particularly, how Clec12a intercepts lipid raft-originated signaling cascade remains to be elucidated. Here, we found that the ITIM motif of Clec12a is dispensable for its inhibition of MSU-mediated signaling; instead, the transmembrane domain of Clec12a disrupts MSU-induced lipid raft recruitment and thus attenuates downstream signals. Single amino acid mutagenesis study showed the critical role of phenylalanine in the transmembrane region for the interactions between C-type lectin receptors and lipid rafts, which is critical for the regulation of MSU-mediated lipid sorting and phagocyte activation. Overall, our study provides new insights for the molecular mechanisms of solid particle-induced immune activation and may lead to new strategies in inflammation control.
Insights
Monosodium uric acid (MSU) crystals activate immune cells by altering cell membranes. Clec12a protein blocks this activation by disrupting lipid rafts, offering new targets for gout inflammation control.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Monosodium uric acid (MSU) crystals, the cause of gout, activate innate immune responses.
- MSU-induced lipid sorting on plasma membranes triggers Syk phosphorylation and phagocyte activation.
- Clec12a, a C-type lectin receptor, recognizes MSU and suppresses immune activation, but its integration into lipid raft signaling is unclear.
Purpose of the Study:
- To elucidate how Clec12a regulates MSU-mediated inflammatory responses.
- To investigate the role of Clec12a in intercepting lipid raft-originated signaling cascades.
- To identify the specific domains and residues of Clec12a critical for its function.
Main Methods:
- Utilized single amino acid mutagenesis to study Clec12a function.
- Investigated the role of Clec12a's ITIM motif and transmembrane domain.
- Analyzed the disruption of MSU-induced lipid raft recruitment by Clec12a.
Main Results:
- The ITIM motif of Clec12a is not essential for inhibiting MSU-mediated signaling.
- Clec12a's transmembrane domain disrupts MSU-induced lipid raft recruitment, attenuating downstream signals.
- A phenylalanine residue in Clec12a's transmembrane region is critical for C-type lectin receptor-lipid raft interactions and regulating MSU-induced phagocyte activation.
Conclusions:
- Clec12a regulates MSU-induced immune activation by disrupting lipid raft organization, independent of its ITIM motif.
- Specific interactions within Clec12a's transmembrane domain are key to controlling MSU-mediated lipid sorting and phagocyte activation.
- This study offers novel insights into solid particle-induced immune activation and potential strategies for inflammation management.
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