Title

Mechanisms of RelB regulation during early dendritic cell differentiation

Date of Award

2005

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Microbiology and Immunology

First Committee Member

Kelvin P. Lee, Committee Chair

Abstract

The NF-kappaB transcription factor RelB is essential for proper development and function of dendritic cells (DCs). While NF-kappaB members exist as homo/heterodimers that are retained in the cytoplasm by inhibitory IkappaBs, RelB shows a restricted pairing ability and its dimers are not inhibited by IkappaB, resulting in constitutive nuclear activity in many tissues. RelB expression is transcriptionally regulated by NF-kappaB and increases very early during the differentiation of DCs. In this dissertation we examined how RelB transcription is regulated in KG1, a CD34+ cell line model of a DC progenitor. We analyzed also the very similar KG1a subclone, which fails to differentiate into DCs. We have found that RelB is upregulated exclusively during DC differentiation of KG1 cells through both an increase in transcription initiation and by overcoming a transcriptional attenuation between exons 4 and 5 of the RELB gene. In contrast, during the same differentiating conditions KG1a cells failed to increase the levels of transcription initiation and to fully elongate transcripts beyond exon 5.The significance of PKC signaling in the generation of DCs is suggested by the direct differentiation of CD34+ HPCs into DCs after PMA treatment. We have now found that restoration of protein kinase C beta II (PKCbetaII) expression in KG1a cells establishes a phenotype similar to that of KG1 (which expresses PKCbetaII naturally) and allows their differentiation into DCs, as assessed by development of DC morphology, upregulation of DC-specific markers, and allogeneic T cell stimulation. Further analysis of PKCbetaII-transfected KG1a cells revealed a downregulation in the expression of the NF-Bkappa proteins p105, p100, p50, RelA (p65) and RelB. As observed for KG1 cells, the levels of RelB protein increase during differentiation of transfected cells due to a higher transcriptional initiation and elongation. We show that both regulatory mechanisms can act independently and are sensitive to the levels of PKC signaling. Altogether, the data shows that NF-kappaB expression, and therefore its activity, can be further regulated by transcriptional attenuation and that PKCbetaII is an important mediator of DC differentiation probably due to a central role in the regulation of RelB and other NF-kappaB members.

Keywords

Biology, Molecular; Health Sciences, Immunology

Link to Full Text

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