Regulation of constitutive p50/c-Rel activity via proteasome inhibitor-resistant IkappaBalpha degradation in B cells.
Constitutive NF-kappaB activity has emerged as an important cell survival component of physiological and pathological processes, including B-cell development. In B cells, constitutive NF-kappaB activity includes p50/c-Rel and p52/RelB heterodimers, both of which are critical for proper B-cell development. We previously reported that WEHI-231 B cells maintain constitutive p50/c-Rel activity via selective degradation of IkappaBalpha that is mediated by a proteasome inhibitor-resistant, now termed PIR, pathway. Here, we examined the mechanisms of PIR degradation by comparing it to the canonical pathway that involves IkappaB kinase-dependent phosphorylation and beta-TrCP-dependent ubiquitylation of the N-terminal signal response domain of IkappaBalpha. We found a distinct consensus sequence within this domain of IkappaBalpha for PIR degradation. Chimeric analyses of IkappaBalpha and IkappaBbeta further revealed that the ankyrin repeats of IkappaBalpha, but not IkappaBbeta, contained information necessary for PIR degradation, thereby explaining IkappaBalpha selectivity for the PIR pathway. Moreover, we found that PIR degradation of IkappaBalpha and constitutive p50/c-Rel activity in primary murine B cells were maintained in a manner different from B-cell-activating-factor-dependent p52/RelB regulation. Thus, our findings suggest that nonconventional PIR degradation of IkappaBalpha may play a physiological role in the development of B cells in vivo.
O'Connor
Shelby
S
Department of Pharmacology, University of Wisconsin, 301 SMI, 1300 University Ave., Madison, WI 53706, USA.
Shumway
Stuart D
SD
Amanna
Ian J
IJ
Hayes
Colleen E
CE
Miyamoto
Shigeki
S
D000818:Animals; D053264:B-Cell Activating Factor; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009097:Multienzyme Complexes / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D020569:Proto-Oncogene Proteins c-rel / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
D053264:B-Cell Activating Factor; D020672:I-kappa B Proteins; D008565:Membrane Proteins; D009097:Multienzyme Complexes; D020569:Proto-Oncogene Proteins c-rel; D011993:Recombinant Fusion Proteins; C505720:Tnfsf13b protein, mouse; D014409:Tumor Necrosis Factor-alpha; D017346:Protein Serine-Threonine Kinases; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex