Demonstration of an activation regulated NF-kappaB/I-kappaBalpha complex in human platelets.

In eukaryotic cells, the ubiquity of the signaling system of transcription factor nuclear factor-kappa B (NF-kappaB)/I-kappa B (I-kappaB) is undisputed. Numerous studies have reported that the NF-kappaB/I-kappaB complex plays a pivotal role in regulating gene expression controlling cell differentiation, cell proliferation, inflammation, oncogenesis, and apoptosis. Here we show that NF-kappaB/I-kappaB families exist in human platelets, natural anuclear corpuscles derived from megakaryocytes. Moreover, the I-kappaB kinase (IKK) is present and may phosphorylate I-kappaB during platelet activation. Coupled with intracellular calcium flux, this leads to I-kappaB dissociation from the NF-kappaB/I-kappaB complex and proteolysis. The NF-kappaB/I-kappaB proteins may have function independent of gene regulation in platelets.