8wyr
Cryo-EM structure of human CD5L bound to IgM-Fc/J
Structural highlights
DiseaseIL2_HUMAN Note=A chromosomal aberration involving IL2 is found in a form of T-cell acute lymphoblastic leukemia (T-ALL). Translocation t(4;16)(q26;p13) with involves TNFRSF17. FunctionIL2_HUMAN Produced by T-cells in response to antigenic or mitogenic stimulation, this protein is required for T-cell proliferation and other activities crucial to regulation of the immune response. Can stimulate B-cells, monocytes, lymphokine-activated killer cells, natural killer cells, and glioma cells.CD5L_HUMAN Secreted protein that acts as a key regulator of lipid synthesis: mainly expressed by macrophages in lymphoid and inflamed tissues and regulates mechanisms in inflammatory responses, such as infection or atherosclerosis. Able to inhibit lipid droplet size in adipocytes. Following incorporation into mature adipocytes via CD36-mediated endocytosis, associates with cytosolic FASN, inhibiting fatty acid synthase activity and leading to lipolysis, the degradation of triacylglycerols into glycerol and free fatty acids (FFA). CD5L-induced lipolysis occurs with progression of obesity: participates in obesity-associated inflammation following recruitment of inflammatory macrophages into adipose tissues, a cause of insulin resistance and obesity-related metabolic disease. Regulation of intracellular lipids mediated by CD5L has a direct effect on transcription regulation mediated by nuclear receptors ROR-gamma (RORC). Acts as a key regulator of metabolic switch in T-helper Th17 cells. Regulates the expression of pro-inflammatory genes in Th17 cells by altering the lipid content and limiting synthesis of cholesterol ligand of RORC, the master transcription factor of Th17-cell differentiation. CD5L is mainly present in non-pathogenic Th17 cells, where it decreases the content of polyunsaturated fatty acyls (PUFA), affecting two metabolic proteins MSMO1 and CYP51A1, which synthesize ligands of RORC, limiting RORC activity and expression of pro-inflammatory genes. Participates in obesity-associated autoimmunity via its association with IgM, interfering with the binding of IgM to Fcalpha/mu receptor and enhancing the development of long-lived plasma cells that produce high-affinity IgG autoantibodies (By similarity). Also acts as an inhibitor of apoptosis in macrophages: promotes macrophage survival from the apoptotic effects of oxidized lipids in case of atherosclerosis (PubMed:24295828). Involved in early response to microbial infection against various pathogens by acting as a pattern recognition receptor and by promoting autophagy (PubMed:16030018, PubMed:24223991, PubMed:24583716, PubMed:25713983).[UniProtKB:Q9QWK4][1] [2] [3] [4] [5] Publication Abstract from PubMedCD5 antigen-like (CD5L), also known as Spalpha or AIM (Apoptosis inhibitor of macrophage), emerges as an integral component of serum immunoglobulin M (IgM). However, the molecular mechanism underlying the interaction between IgM and CD5L has remained elusive. In this study, we present a cryo-electron microscopy structure of the human IgM pentamer core in complex with CD5L. Our findings reveal that CD5L binds to the joining chain (J chain) in a Ca(2+)-dependent manner and further links to IgM via a disulfide bond. We further corroborate recently published data that CD5L reduces IgM binding to the mucosal transport receptor pIgR, but does not impact the binding of the IgM-specific receptor FcmuR. Additionally, CD5L does not interfere with IgM-mediated complement activation. These results offer a more comprehensive understanding of IgM and shed light on the function of the J chain in the immune system. CD5L associates with IgM via the J chain.,Wang Y, Su C, Ji C, Xiao J Nat Commun. 2024 Sep 27;15(1):8397. doi: 10.1038/s41467-024-52175-y. PMID:39333069[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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