Publications

The specific signal transduction function of the gamma c subunit in the interleukin (IL) 2, IL-4, IL-7, IL-9, and IL-15 receptor complexes remains undefined. The present structure-function analyses demonstrated that the entire cytoplasmic tail of gamma c could be functionally replaced in the IL-2 receptor (IL-2R) signaling complex by a severely truncated erythropoietin receptor cytoplasmic domain lacking tyrosine residues. Heterodimerization of IL-2R beta with either gamma c or the truncated erythropoietin receptor chain led to an array of specific signals normally derived from the native IL-2R despite the substitution of Janus kinase JAK2 for JAK3 in the receptor complex. These findings thus suggest a model in which the gamma c subunit serves as a common and generic "trigger" chain by providing a nonspecific Janus kinase for signaling program initiation, while signal specificity is determined by the unique "driver" subunit in each of the gamma c- containing receptor complexes. Furthermore, these results may have important functional implications for the asymmetric design of many cytokine receptor complexes and the evolutionary design of receptor subfamilies that share common trigger or driver subunits.

Interleukin-8 (IL-8) is an 8 kD chemokine and angiogenic factor produced by alveolar macrophages, endothelial cells, monocytes, fibroblasts, T lymphocytes, and epithelial cells in response to a variety of stimuli, including LPS, TNF-alpha, IL-1, IL-7, and hypoxia. Pulmonary tumors produce a variety of growth factors and cytokines that may act in both autocrine and paracrine fashion. A549, a well-characterized human lung adenocarcinoma line, was cloned for different levels of IL-8 production by limiting dilution. Clone 3B4 produced 361 +/- 73 pg/ml, and clone 2B2 produced 7818 +/- 614 pg/ml of IL-8 (p = 0.003). Clone 3B4 proliferated at 1.7 times the rate of 2B2. Anti-IL-8 reversed the decrement in proliferation of clone 2B2 by 50%, but recombinant IL-8 decreased the proliferation of 3B4 by 40-55% compared with control. In addition to A549, three other non-small cell lung cancer (NSCLC) lines showed significantly decreased proliferation in response to exogenous recombinant IL-8 (5-30 ng/ml; p < 0.05). These findings suggest that in addition to its chemotactic and angiogenic activities, IL-8 may inhibit lung tumor proliferation by both autocrine and paracrine pathways.