cytokinereceptor

A cytokine receptor is a cell-surface or soluble receptor that binds a cytokine, a small signaling protein that modulates immune responses, inflammation, hematopoiesis, and development. Binding of a cytokine to its receptor initiates intracellular signaling that alters gene expression and cellular behavior. Receptors can be membrane-bound or exist as soluble forms that modulate activity by sequestering cytokines.

Cytokine receptors are diverse and are commonly grouped into families based on structural features and signaling partners. Class I (hematopoietin) receptors include many interleukin receptors and often assemble with a shared signaling subunit such as the common gamma chain. Class II receptors include those for interferons and related cytokines. There are also other families, such as the interleukin-1 receptor/Toll-like receptor superfamily and the TNF receptor superfamily, each with distinct extracellular structures and downstream adapters. Across these families, receptor units may exist as single chains or as heterodimers or oligomers that come together upon ligand binding.

Signal transduction from cytokine receptors frequently involves phosphorylation cascades. Many Class I and II receptors associate with Janus kinases (JAKs) that phosphorylate the receptor, creating docking sites for STAT transcription factors. Phosphorylated STATs dimerize and move to the nucleus to regulate target genes. Other receptors, such as those in the TNF receptor family, recruit adaptor proteins like TRAFs and activate NF-κB or MAPK pathways. Regulation of receptor activity occurs through mechanisms such as receptor internalization, degradation, and negative feedback proteins like SOCS.

Therapeutically, cytokine receptors are targets for monoclonal antibodies, receptor fusion proteins acting as decoys, and other agents to treat autoimmune diseases, cancers, and hematologic disorders. Dysfunction or dysregulation of cytokine receptors can contribute to immune deficiencies and inflammatory conditions.