S. Doerre et Rb. Corley, Constitutive nuclear translocation of NF-kappa B in B cells in the absenceof I kappa B degradation, J IMMUNOL, 163(1), 1999, pp. 269-277
Members of the NF-kappa B/Rel family of transcription factors are involved
in many aspects of B lymphocyte development and function. NF-kappa B is con
stitutively active in these cells, in contrast with most other cell types.
In the inactive form, NF-kappa B/Rel proteins are sequestered in the cytopl
asm by members of the I kappa B family of NF-kappa B inhibitors, When activ
ated, NF-kappa B is translocated to the nucleus, a process that involves th
e phosphorylation and proteasomal degradation of I kappa B proteins. Thus,
NF-kappa B activation is accompanied by the rapid turnover of I kappa B pro
teins. We show that while this "classical" mode of NF-kappa B activation is
a uniform feature of IgM(+) B cell lines, all IgG(+) B cells analyzed cont
ain nuclear NF-kappa B yet have stable I kappa B alpha, I kappa B beta, and
I kappa B epsilon. Furthermore, I kappa beta epsilon levels are at least 1
0 times lower in IgG(+) B cells than in IgM(+) B cells, an additional indic
ation that the regulation of constitutive NF-kappa B activity in these two
types of B cells is fundamentally different. These data imply the existence
of a novel mechanism of NF-kappa B activation in IgG(+) B cells that opera
tes independently of I kappa B degradation. They further suggest that diffe
rent isoforms of the B cell receptor may have distinct roles in regulating
NF-kappa B activity.