There is considerable functional redundancy amongst Class I helical cytokine receptors. Signaling via these receptors has a myriad of roles, including a major influence on immunity and hematopoiesis. The receptors for Class I helical cytokines consist of various receptor chains that associate in higher order homo- and heterotypic complexes. Class I helical cytokines represent the largest group of cytokines and utilize a family of cell-surface receptors that are structurally divergent from those employed by other cytokines, such as the TNF receptor family and receptor tyrosine kinases. These polypeptides are produced and secreted by cells in response to many stimuli and mediate their effects by binding to specific receptors on the surface of target cells. Since then, only relatively limited lineage-specific diversification within the different Class I receptor structural groups has occurred.Ĭytokines are a class of proteins that includes interleukins (ILs), interferons (IFNs), colony-stimulating factors (CSFs), and tumor necrosis factors (TNFs). This study suggests that the majority of diversification of this receptor family occurred after the divergence of urochordates and vertebrates approximately 794 million years ago (MYA), but before the divergence of ray-finned from lobe-finned fishes around 476 MYA. This allowed the identification of 27 core receptors belonging to the last common ancestor of teleosts and mammals. In contrast, 36 Class I cytokine receptors were present in zebrafish, including representative members for each of the five structural groups found in mammals. Only two Class I receptors were identified in sea squirt, one with homology to the archetypal GP130 receptor, and the other with high conservation with the divergent orphan receptor CLF-3. To address this we have used bioinformatics to analyze the Class I receptor repertoire in sea squirt ( Ciona intestinalis) and zebrafish ( Danio rerio). However, the evolution of the genes encoding them remains poorly understood. The Class I cytokine receptors have a wide range of actions, including a major role in the development and function of immune and blood cells.
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