| First Author | King AM | Year | 2007 |
| Journal | J Immunol | Volume | 178 |
| Issue | 6 | Pages | 3521-9 |
| PubMed ID | 17339447 | Mgi Jnum | J:144286 |
| Mgi Id | MGI:3830590 | Doi | 10.4049/jimmunol.178.6.3521 |
| Citation | King AM, et al. (2007) Accelerated Notch-dependent degradation of E47 proteins in aged B cell precursors is associated with increased ERK MAPK activation. J Immunol 178(6):3521-9 |
| abstractText | The transcriptional regulator E47, encoded by the E2A gene, is crucial to B lymphopoiesis. In BALB/c senescent mice (approximately 2 years old), the incidence of E47-expressing pro-B cells in vivo and E47 protein steady state levels in B cell precursors in vitro were reduced. Poor expression of E47 protein was a consequence of accelerated proteasome-mediated turnover and was associated with heightened ubiquitin modification of E2A-encoded proteins in aged B cell precursors. Both MAPK and Notch activity have been previously associated with E2A-encoded protein stability in lymphocytes. Aged B cell precursors exhibited heightened levels of MAPK activity reflected in increased levels of phospho-ERK proteins. Phosphorylation of E2A-encoded proteins was also increased in aged B cell precursors and pharmacologic inhibition of MEK-1 resulted in a partial restoration of their E47 protein. Both Notch proteins and their Delta-like ligands were detected comparably in young and aged B cell precursors. Either inhibition of Notch activation via gamma-secretase or Ab blockade of Notch-Delta-like ligand interactions partially restored E47 expression in aged B cell precursors. We hypothesize that increased MAPK activity promotes phosphorylation of E2A-encoded protein in aged B cell precursors. Subsequently, E2A-encoded proteins undergo ubiquitination and accelerated degradation in a Notch-dependent process. The dysregulation of E2A-encoded protein expression may contribute to the reductions seen in early B lymphopoiesis during murine senescence. |
