Distinct Spatial Relationship of the Interleukin‐9 Receptor with Interleukin‐2 Receptor and Major Histocompatibility Complex Glycoproteins in Human T Lymphoma Cells

The interleukin-9 receptor (IL-9R) consists of an α subunit and a γ(c) chain that are shared with other cytokine receptors, including interleukin-2 receptor (IL-2R), an important regulator of T cells. We previously showed that IL-2R is expressed in common clusters with major histocompatibility complex (MHC) glycoproteins in lipid rafts of human T lymphoma cells, which raised the question about what the relationship between clusters of IL-2R/MHC and IL-9R is. Confocal microscopy colocalization and fluorescence resonance energy transfer experiments capable of detecting membrane protein organization at different size scales revealed nonrandom association of IL-9R with IL-2R/MHC clusters at the surface of human T lymphoma cells. Accommodation of IL-9Rα in membrane areas segregated from the IL-2R/MHC domains was also detected. The bipartite nature of IL-9R distribution was mirrored by signal transducer and activator of transcription (STAT) activation results. Our data indicate that co-compartmentalization with MHC glycoproteins is a general property of γ(c) receptors. Distribution of receptor chains between different membrane domains may regulate their function.