The role of CD150 surface receptor in regulation of topology and expression of p50 and p65 NF-kB in normal B cells

Gordiienko I.M.1, Kovalevska L.M.2, Shlapatska L.M.1, Sidorenko S.P.1

I.M. Gordiienko, L.M. Kovalevska, L.M. Shlapatska, S.P. Sidorenko

R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology NAS of Ukraine, Kyiv, Ukraine

Introduction: CD150 receptor is widely expressed in hematopoietic cell lineage and is involved in lymphocyte activation, differentiation and apoptosis via regulation of signal transduction pathways. Moreover, CD150 is expressed on malignant cells at Hodgkin’s lymphoma and diffuse large B cell lymphoma that are characterized by enhanced level of NF-kB activation. CD150-mediated signal transduction pathways are not fully understood. Particularly, it is not clear whether CD150 is involved in regulation of NF-kB transcription factors that play a key role in immune system. Aim of our study was to find the potential role of CD150 in regulation of NF-kB transcription factors function in normal human B-cells. Methods: Dense human tonsillar B cells were obtained in Percoll gradient, were stimulated via CD150 cell surface receptor, followed by immunofluorescence staining with 3D deconvolution and Western blot analysis. Results: In dense B cells that comprise IgD+ naive cells p65 was predominantly localized in cytoplasm and p50 — in the cialis cheapest nucleus, while several p65/p50 heterodimers were observed in nucleus, but not in cytoplasm. After 90 min of CD150 ligation p50 was also detected in cytoplasm. Stimulation of dense B cells via CD150 for 16 h resulted in complete translocation of p50 and p65 from nucleus to the cytoplasm. Further cell stimulation via CD150 up to 24 h resulted in returning only p50 back to the nucleus, although, a high level of p50 was still observed in cytoplasm where it was colocalized with p65. Western blot analysis has shown that after 24 hours of CD150 crosslinking on dense B cells, the expression level of p50 did not change, however, p65 level was slightly enhanced. The expression level of IkBα was significantly increased after 24 hour of CD150 ligation that points on the role of IkBα in p65 and p50 subunits re-exportation from the nucleus and sequestering in the cytoplasm. Conclusions: CD150 is involved in regulation of gene expression in B cells via intracellular relocalization of both p50 and p65 and minor upregulation of p65 expression level. Thus CD150 may also contribute to the regulation of NF-kB1 activation in CD150 expressing malignant B lymphocytes.

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