ABSTRACT
New research shows that specialized epithelial cells (tuft cells) are major producers of lipid mediators (leukotrienes) that drive allergic inflammation and host defense against helminth parasites. (See the related Research Article by Ualiyeva et al.).
Subject(s)
Leukotrienes , Tomography, X-Ray ComputedABSTRACT
The interleukin 12 (IL-12) family of cytokines regulates T cell functions and is key for the orchestration of immune responses. Each heterodimeric IL-12 family member is a glycoprotein. However, the impact of glycosylation on biogenesis and function of the different family members has remained incompletely defined. Here, we identify glycosylation sites within human IL-12 family subunits that become modified upon secretion. Building on these insights, we show that glycosylation is dispensable for secretion of human IL-12 family cytokines except for IL-35. Furthermore, our data show that glycosylation differentially influences IL-12 family cytokine functionality, with IL-27 being most strongly affected. Taken together, our study provides a comprehensive analysis of how glycosylation affects biogenesis and function of a key human cytokine family and provides the basis for selectively modulating their secretion via targeting glycosylation.
Subject(s)
Interleukin-12/metabolism , Interleukins/metabolism , Glycosylation , HEK293 Cells , Humans , Interleukin-12/genetics , Interleukin-12/immunology , Interleukin-23/genetics , Interleukin-23/immunology , Interleukin-23/metabolism , Interleukins/genetics , Interleukins/immunology , Sequence Alignment , Sequence Homology, Amino AcidABSTRACT
The functionality of most secreted proteins depends on their assembly into a defined quaternary structure. Despite this, it remains unclear how cells discriminate unassembled proteins en route to the native state from misfolded ones that need to be degraded. Here we show how chaperones can regulate and control assembly of heterodimeric proteins, using interleukin 23 (IL-23) as a model. We find that the IL-23 α-subunit remains partially unstructured until assembly with its ß-subunit occurs and identify a major site of incomplete folding. Incomplete folding is recognized by different chaperones along the secretory pathway, realizing reliable assembly control by sequential checkpoints. Structural optimization of the chaperone recognition site allows it to bypass quality control checkpoints and provides a secretion-competent IL-23α subunit, which can still form functional heterodimeric IL-23. Thus, locally-restricted incomplete folding within single-domain proteins can be used to regulate and control their assembly.
