Characterization of the human B cell stimulatory factor 1 receptor.

Abstract

125I-labeled recombinant human B cell stimulatory factor 1 (BSF-1) was used to characterize receptors specific for this lymphokine on in vitro cell lines representing human B, T, and hematopoietic lineages, as well as on adherent cell lines of epithelial and endothelial origin, and on primary human gingival fibroblasts. BSF-1 binding was extremely rapid and saturable at both 4 and 37 degrees C, with a slow dissociation rate. On all human cell types examined, BSF-1 bound to a single class of high-affinity receptor (less than 3,000 receptors per cell) with a Ka of 0.5-1.0 X 10(10)/M. Human BSF-1 also bound to cell lines of simian but not murine origin. Comparison of kinetic characteristics obtained with a yeast-derived hyperglycosylated form of BSF-1 (Mr 60,000) and N-glycanase-treated, sugar-free BSF-1 (Mr 15,000) showed no significant differences. Among a panel of lymphokines and growth hormones, only unlabeled human BSF-1 was able to compete for the binding of 125I-labeled human BSF-1. Affinity crosslinking experiments resulted in the identification on both Raji cells and on primary human gingival fibroblasts of a receptor subunit with an average Mr of 139,000. These studies show that the BSF-1 receptor on human cells has an extremely broad cellular distribution, while further supporting the notion that the ability of BSF-1 to mediate a spectrum of biological activities cannot be accounted for by overt differences in the receptor for this lymphokine on different cell lineages.

Essential role of endocytosis for Interleukin-4 receptor mediated JAK/STAT signalling

“…However, our FCCS experiments demonstrated that the two-dimensional dissociation constants of the IL-4R complexes are of the order of several hundred to a thousand receptors per µm 2 (Gandhi et al, 2014). At endogenous IL-4R cell surface densities of 1-10 receptors per µm 2 (Lowenthal et al, 1988;Ohara and Paul, 1987;Park et al, 1987), the fraction of subunits entering active heterodimers would thus be negligible even with saturating ligand levels. Productive signalling therefore demands a subcellular concentration step that is missing from current models of CKR activation.…”

“…After selecting regions of interest by analysing GFP immunofluorescence, we identified cortical endosomes within these areas based on their multivesicular ultrastructure and localization. Even though the endogenous cell surface levels of IL-4Rα are very low in most cells (1-10 receptors/µm 2 ) (Lowenthal et al, 1988;Ohara and Paul, 1987;Park et al, 1987), we could detect a specific localized signal (from 10-nm gold particles conjugated to protein A) for the biotinylated IL-4 within these putative cortical endosomes using an anti-biotin antibody (Fig. 4E).…”

IFN-γ Suppresses STAT6 Phosphorylation by Inhibiting Its Recruitment to the IL-4 Receptor

“…IL-4 is the major determinant in directing naive CD4 ϩ T cells to differentiate into Th2 cells (4 -7). It mediates its function by binding and stimulating the IL-4R ␣-chain (8,9). Ligand-bound IL-4R ␣-chain recruits common ␥-chain and its associated kinase Jak3 (10,11).…”

Aspects of Receptor Binding and Signalling of Interleukin-4 Investigated by Site-directed Mutagenesis and NMR Spectroscopy

“…It occurs at the relatively low flgure of 150 to 2500 molecules per target cell (CabriJlat et al, 1987;Park et al, 1987). A single dissociation constant of ::::: 100 pM has been determined for the receptor-cytokine interaction.…”