Bolshakova A, Magnusson KE, Pinaev G, Petukhova O. Functional compartmentalisation of NF-kB-associated proteins in A431 cells.
Cell Biol Int 2015;
37:387-96. [PMID:
23408724 DOI:
10.1002/cbin.10053]
[Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 01/10/2013] [Indexed: 12/30/2022]
Abstract
NF-kB proteins belong to a family of ubiquitous transcription factors involved in a number of cellular responses. While the pathways of NF-kB activation and input into the regulation of gene activity have been comprehensively investigated, its cytoplasmic functions are poorly understood. In this study we addressed effects of the compartmentalisation of NF-kB proteins RelA/p65 and p50 in relation to the inhibitor IkB-a, using fibronectin (FN) and epidermal growth factor (EGF) for environmental stimulation of epidermoid carcinoma A431 cells. We thus assessed the presence of NF-kB family proteins in the cytosol, membrane, nuclear and cytoskeletal fractions with a special attention to the cytoskeletal fraction to define whether NFkB was active or not. Sub-cellular fractionation demonstrated that the proportion of RelA/p65 differed in diverse sub-cellular fractions, and that the cytoskeleton harboured about 7% thereof. Neither the nuclear nor the cytoskeleton fraction did contain IkB-a. The cytoskeleton binding of RelA/p65 and p50 was further confirmed by co-localisation and electron microscopy data. During 30-min EGF stimulation similar dynamics were found for RelA/p65 and IkB-a in the cytosol, RelA/p65 and p50 in the nucleus and p50 and IkB-a in the membrane. Furthermore, EGF stimulation for 30 min resulted in a threefold accumulation of RelA/p65 in cytoskeletal fraction. Our results suggest that nuclear-, membrane- and cytoskeleton-associated NF-kB are dynamic and comprise active pools, whereas the cytoplasmic is more constant and likely non-active due to the presence of IkB-a. Moreover, we discovered the existence of a dynamic, IkB-a-free pool of RelA/p65 associated with cytoskeletal fraction, what argues for a special regulatory role of the cytoskeleton in NF-kB stimulation.
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