ABSTRACT
Interleukin (IL)-11 signaling is involved in various processes, including epithelial intestinal cell regeneration and embryo implantation. IL-11 signaling is initiated upon binding of IL-11 to IL-11R1 or IL-11R2, two IL-11α-receptor splice variants, and gp130. Here, we show that IL-11 signaling via IL-11R1/2:gp130 complexes occurs on both the apical and basolateral sides of polarized cells, whereas IL-6 signaling via IL-6R:gp130 complexes is restricted to the basolateral side. We show that basolaterally supplied IL-11 is transported and released to the apical extracellular space via transcytosis in an IL-11R1-dependent manner. By contrast, IL-6R and IL-11R2 do not promote transcytosis. In addition, we show that transcytosis of IL-11 is dependent on the intracellular domain of IL-11R1 and that synthetic transfer of the intracellular domain of IL-11R1 to IL-6R promotes transcytosis of IL-6. Our data define IL-11R as a cytokine receptor with transcytotic activity by which IL-11 and IL-6:soluble IL-6R complexes are transported across cellular barriers.
Subject(s)
Cell Polarity/physiology , Cytokine Receptor gp130/metabolism , Interleukin-11/metabolism , Receptors, Interleukin-11/metabolism , Transcytosis/physiology , Animals , Biological Transport/physiology , Cell Line, Tumor , Dogs , Embryo Implantation/physiology , HeLa Cells , Humans , Interleukin-6/metabolism , Madin Darby Canine Kidney Cells , Receptors, Interleukin-6/metabolism , Signal Transduction/physiologyABSTRACT
Interleukin (IL)-11 has been shown to be a crucial factor for intestinal tumorigenesis, lung carcinomas, and asthma. IL-11 is thought to exclusively mediate its biological functions through cell-type-specific expression of the membrane-bound IL-11 receptor (IL-11R). Here, we show that the metalloprotease ADAM10, but not ADAM17, can release the IL-11R ectodomain. Chimeric proteins of the IL-11R and the IL-6 receptor (IL-6R) revealed that a small juxtamembrane portion is responsible for this substrate specificity of ADAM17. Furthermore, we show that the serine proteases neutrophil elastase and proteinase 3 can also cleave the IL-11R. The resulting soluble IL-11R (sIL-11R) is biologically active and binds IL-11 to activate cells. This IL-11 trans-signaling pathway can be inhibited specifically by the anti-inflammatory therapeutic compound sgp130Fc. In conclusion, proteolysis of the IL-11R represents a molecular switch that controls the IL-11 trans-signaling pathway and widens the number of cells that can be activated by IL-11.
Subject(s)
ADAM Proteins/immunology , Amyloid Precursor Protein Secretases/immunology , Interleukin-11/immunology , Leukocyte Elastase/immunology , Membrane Proteins/immunology , Monocytes/immunology , Myeloblastin/immunology , Receptors, Interleukin-11/immunology , ADAM Proteins/genetics , ADAM10 Protein , ADAM17 Protein , Amino Acid Sequence , Amyloid Precursor Protein Secretases/genetics , Anti-Inflammatory Agents/pharmacology , Cell Line , Gene Expression Regulation , HEK293 Cells , Humans , Inflammation , Interleukin-11/genetics , Leukocyte Elastase/genetics , Membrane Proteins/genetics , Molecular Sequence Data , Monocytes/drug effects , Monocytes/pathology , Myeloblastin/genetics , Protein Binding , Proteolysis , Receptors, Interleukin-11/genetics , Receptors, Interleukin-6/genetics , Receptors, Interleukin-6/immunology , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunology , Recombinant Fusion Proteins/pharmacology , Signal TransductionABSTRACT
Interleukin (IL)-6 and IL-11 are the only canonical members of the IL-6 family of cytokines that induce signaling through a homodimer of the common ß-receptor glycoprotein (gp)130. A pre-requisite for signal transduction is the initial binding of the cytokines to their unique α-receptors, IL-6R and IL-11R. The cell-type specific expression of the two receptors determines the target cells of IL-6 and IL-11, because gp130 is ubiquitously expressed. However, ciliary neurotrophic factor (CNTF) and IL-27p28/IL-30 have been described as additional ligands for the IL-6R, underlining a remarkable plasticity among the cytokines of the IL-6 family and their receptors. In this study, we show that neither IL-6 nor IL-11 can bind to and signal through the α-receptor of the respective other cytokine. We further create eight chimeric IL-6/IL-11 receptors, which are all biologically active. We find that the domains D1 to D3, which contain the cytokine binding module (CBM), determine which cytokine can activate the chimeric receptor, whereas the stalk region, the transmembrane region, or the intracellular region do not participate in the ligand selectivity of the receptor and are therefore interchangeable between IL-6R and IL-11R. These results suggest a modular organization of the IL-6R and IL-11R, and a similar signal transduction complex of the two cytokines.
Subject(s)
Interleukin-11 Receptor alpha Subunit/chemistry , Interleukin-6 Receptor alpha Subunit/chemistry , Models, Molecular , Receptors, Interleukin-6/chemistry , Animals , Binding Sites , Cell Line , Cell Proliferation , Cytokine Receptor gp130/agonists , Cytokine Receptor gp130/chemistry , Cytokine Receptor gp130/genetics , Cytokine Receptor gp130/metabolism , Humans , Interleukin-11/genetics , Interleukin-11/metabolism , Interleukin-11 Receptor alpha Subunit/agonists , Interleukin-11 Receptor alpha Subunit/genetics , Interleukin-11 Receptor alpha Subunit/metabolism , Interleukin-6/genetics , Interleukin-6/metabolism , Interleukin-6 Receptor alpha Subunit/agonists , Interleukin-6 Receptor alpha Subunit/genetics , Interleukin-6 Receptor alpha Subunit/metabolism , Ligands , Mice , Peptide Fragments/agonists , Peptide Fragments/chemistry , Peptide Fragments/genetics , Peptide Fragments/metabolism , Protein Interaction Domains and Motifs , Protein Structure, Tertiary , Protein Subunits , Receptors, Interleukin-6/agonists , Receptors, Interleukin-6/genetics , Receptors, Interleukin-6/metabolism , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Signal TransductionABSTRACT
Signaling of the pleiotropic cytokine Interleukin-6 (IL-6) is coordinated by membrane-bound and soluble forms of the IL-6 receptor (IL-6R) in processes called classic and trans-signaling, respectively. The soluble IL-6R is mainly generated by ADAM10- and ADAM17-mediated ectodomain shedding. Little is known about the role of the 52-amino acid-residue-long IL-6R stalk region in shedding and signal transduction. Therefore, we generated and analyzed IL-6R stalk region deletion variants for cleavability and biological activity. Deletion of 10 amino acids of the stalk region surrounding the ADAM17 cleavage site substantially blocked IL-6R proteolysis by ADAM17 but only slightly affected proteolysis by ADAM10. Interestingly, additional deletion of the remaining five juxtamembrane-located amino acids also abrogated ADAM10-mediated IL-6R shedding. Larger deletions within the stalk region, that do not necessarily include the ADAM17 cleavage site, also reduced ADAM10 and ADAM17-mediated IL-6R shedding, questioning the importance of cleavage site recognition. Furthermore, we show that a 22-amino acid-long stalk region is minimally required for IL-6 classic signaling. The gp130 cytokine binding sites are separated from the plasma membrane by ~96 Å. 22 amino acid residues, however, span maximally 83.6 Å (3.8 Å/amino acid), indicating that the three juxtamembrane fibronectin domains of gp130 are not necessarily elongated but somehow flexed to allow IL-6 classic signaling. Our findings underline a dual role of the IL-6R stalk region in IL-6 signaling. In IL-6 trans-signaling, it regulates proper proteolysis by ADAM10 and ADAM17. In IL-6 classic-signaling, it acts as a spacer to ensure IL-6·IL-6R·gp130 signal complex formation.
