Identification of regions in interleukin-1 alpha important for activity

IL-1/IL-1R Signaling in Head and Neck Cancer

Decades ago, the study of cancer biology was mainly focused on the tumor itself, paying little attention to the tumor microenvironment (TME). Currently, it is well recognized that the TME plays a vital role in cancer development and progression, with emerging treatment strategies focusing on different components of the TME, including tumoral cells, blood vessels, fibroblasts, senescent cells, inflammatory cells, inflammatory factors, among others. There is a well-accepted relationship between chronic inflammation and cancer development. Interleukin-1 (IL-1), a potent pro-inflammatory cytokine commonly found at tumor sites, is considered one of the most important inflammatory factors in cancer, and has been related with carcinogenesis, tumor growth and metastasis. Increasing evidence has linked development of head and neck squamous cell carcinoma (HNSCC) with chronic inflammation, and particularly, with IL-1 signaling. This review focuses on the most important members of the IL-1 family, with emphasis on how their aberrant expression can promote HNSCC development and metastasis, highlighting possible clinical applications.

The N-terminal propiece of interleukin 1 alpha is a transforming nuclear oncoprotein

Interleukin 1 alpha (IL-1 alpha) is a pleiotropic cytokine involved in the immune response, inflammatory processes, and hematopoiesis, and acts as a mitogen for several malignant cell types, including acute leukemia and Kaposi sarcoma cells. These diverse activities have been exclusively attributed to the plasma membrane receptor-binding, 17-kDa C-terminal component (mature IL-1 alpha) that results from proteolytic processing of the 31- to 33-kDa precursor protein. No biologic function has been ascribed to the unusually large, 16-kDa N-terminal propiece formed as a result of proteolytic processing of IL-1 alpha. We report that the IL-1 alpha N-terminal propiece is concentrated by means of a nuclear localization sequence within the nuclei of both transfected and leukemic cell lines. Overexpression of this component in glomerular mesangial cells, a model perivascular myofibroblast cell type capable of IL-1 alpha synthesis and processing, results in malignant transformation to a spindle cell-type tumor. The functionally bipartite nature of the IL-1 alpha precursor represents a unique combination of the C-terminal, classical cytokine and an N-terminal nuclear oncoprotein. These findings suggest that nuclear transport of the IL-1 alpha N-terminal component may represent a critical component in the transformation of IL-1 alpha-producing cells in the bone marrow or the perivascular area to a malignant phenotype.

Mapping receptor binding sites in interleukin (IL)-1 receptor antagonist and IL-1 beta by site-directed mutagenesis. Identification of a single site in IL-1ra and two sites in IL-1 beta

Interleukin-1 receptor antagonist (IL-1ra), an IL-1 family member, binds with high affinity to the type I IL-1 receptor (IL-1RI), blocking IL-1 binding but not inducing an IL-1-like response. Extensive site-directed mutagenesis has been used to identify residues in IL-1ra and IL-1 beta involved in binding to IL-1RI. These analyses have revealed the presence of two discrete receptor binding sites on IL-1 beta. Only one of these sites is present on IL-1ra, consisting of residues Trp-16, Gln-20, Tyr-34, Gln-36, and Tyr-147. Interestingly, the absent second site is at the location of the major structural difference between IL-1ra and IL-1 beta, which are otherwise structurally similar. The two receptor binding sites on IL-1 beta are also present on IL-1 alpha. Thus, it appears that the two IL-1 agonist molecules have two sites for IL-1RI binding, and the homologous antagonist molecule, IL-1ra, has only one. Based on these observations, a hypothesis is presented to account for the difference in activity between the agonist and antagonist proteins. It is proposed that the presence of the two receptor binding sites may be necessary for agonist activity.

Refined crystal structure of the interleukin-1 receptor antagonist. Presence of a disulfide link and a cis-proline

Interleukin-1 (IL-1) molecules are cytokines involved in the acute-phase response against infection and injury. Three naturally occurring IL-1 molecules are known, two agonists: IL-1 alpha and IL-1 beta, and one antagonist, the IL-1 receptor antagonist (IL-1ra). Although IL-1 action protects the organism by enhancing the response to pathogens, its overproduction can lead to pathology and has been implicated in disease states that include septic shock, rheumatoid arthritis, graft versus host disease and certain leukemias. The crystal structure of IL-1ra has been solved at 0.21-nm resolution by molecular replacement using the IL-1 beta structure as a search model. The crystals contain two independent IL-1ra molecules which are very similar. IL-1ra has the same fold as IL-1 alpha and IL-1 beta. The fold consists of twelve beta-strands which form a six-stranded beta-barrel, closed on one side by three beta-hairpin loops. Cys69 and Cys116 are linked via a disulfide bond and Pro53 has been built in the cis-conformation. Comparison of the IL-1ra structure with the IL-1 alpha and IL-1 beta structures present in the Protein Data Bank shows that a putative receptor interaction region, involving the N-terminus up to the beginning of strand beta 1 and the loops D and G, is very different in the three IL-1 molecules. Other putative interaction regions, as identified with mutagenesis studies, are structurally conserved and rigid, allowing precise and specific interactions with the IL-1 receptor.