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IL-16 activates the SAPK signaling pathway in CD4+ macrophages
1Department of Immunobiology, Fraunhofer Institute for Toxicology and Molecular Biology, Hannover, Germany. krautwald@ita.fhg.de
Abstract:
IL-16 has been reported as a modulator of T cell activation and was shown to function as chemoattractant factor. The chemotactic activity of IL-16 depends on the expression of CD4 on the surface of target cells, but the intracellular signaling pathways are only now being deciphered. This report describes IL-16 as an additional activator of the stress-activated protein kinase (SAPK) pathway in CD4+ macrophages. Treatment of these cells with recombinant expressed IL-16 leads to the phosphorylation of SEK-1, resulting in activation of the SAPKs p46 and p54. IL-16 stimulation also leads to the phosphorylation of c-Jun and p38 MAPK (mitogen-activated protein kinase), without inducing MAPK-family members ERK-1 and ERK-2. Interestingly, the IL-16-mediated activation of SAPKs and p38 MAPK in macrophages alone induces no detectable apoptotic cell death. These observations suggest specific regulatory functions of IL-16 distinct from the proinflammatory cytokines TNF-alpha and IL-1beta.
Insights
Interleukin-16 (IL-16) activates stress-activated protein kinase (SAPK) pathways in CD4+ macrophages. This signaling pathway activation by IL-16 does not induce cell death, suggesting unique regulatory roles.
Area of Science:
- Immunology
- Cell Signaling
Background:
- Interleukin-16 (IL-16) is known to modulate T cell activation and act as a chemoattractant factor.
- The precise intracellular signaling pathways governing IL-16's chemotactic activity, dependent on CD4 expression, are under investigation.
Purpose of the Study:
- To elucidate the intracellular signaling pathways activated by IL-16 in CD4+ macrophages.
- To investigate IL-16's role in activating the stress-activated protein kinase (SAPK) pathway.
Main Methods:
- Treatment of CD4+ macrophages with recombinant IL-16.
- Analysis of protein phosphorylation, including SEK-1, SAPKs (p46 and p54), c-Jun, p38 MAPK, ERK-1, and ERK-2.
- Assessment of IL-16-induced apoptotic cell death.
Main Results:
- IL-16 activates the SAPK pathway in CD4+ macrophages, leading to SEK-1 phosphorylation and activation of SAPKs p46 and p54.
- IL-16 stimulation results in the phosphorylation of c-Jun and p38 MAPK, but not ERK-1 or ERK-2.
- IL-16-mediated activation of SAPKs and p38 MAPK in macrophages does not induce detectable apoptotic cell death.
Conclusions:
- IL-16 acts as an activator of the SAPK pathway in CD4+ macrophages.
- IL-16 exhibits distinct regulatory functions compared to pro-inflammatory cytokines like TNF-alpha and IL-1beta.