Regulation of the Jun Transcription Factors in B Lymphocytes by the NEDD4 Family E3 Ubiquitin Ligase, Itch

Ubiquitin is a small protein found in all cells containing a nucleus. A key function for this protein is ubiquitylation, the process by which ubiquitin attaches to target proteins to “mark” them for degradation (breaking down) and removal from the cell. Ubiquitylation is an important process for maintaining proper levels of cellular proteins and removing mis-folded proteins to ensure proper cellular function and to prevent disease. E3 Ub ligases are important regulators of the ubiquitylation process because they select the specific proteins (substrates) that are to be degraded. Itch is an E3 Ub ligase that is important in the immune system, as mice deficient in Itch (Itchy mice) develop a fatal autoimmune-like disease. The Jun transcription factors, c-Jun and JunB, are found to be deregulated in the T cells of these mice, and this is believed to contribute to the disease. These proteins are also important for the proper function of B cells and their deregulation has been implicated in some B cell cancers, such as Hodgkin lymphoma. Joel Pearson is determining whether Itch also regulates the Jun proteins in B cells, and how this may contribute to the autoimmune-like disease of Itchy mice. He is also investigating whether Itch regulates the Jun proteins in B and T cell lymphomas where these proteins are expressed at unusually high levels. His hypothesis is that Itch is an important regulator of the Jun proteins in B cells. Furthermore, he believes that Itch is also an important regulator of the Jun proteins in B and T cell lymphomas where these proteins are over-expressed. Understanding how the Jun proteins are regulated in these cells is important for understanding how the autoimmune-like disease of Itch-deficient mice may arise. Deregulation of the Jun proteins also contributes to the pathogenesis of some types of B and T cell lymphomas. Because of this, understanding how they are regulated is important for understanding how these cancers arise and persist. It could also lead to the development of novel ways to treat these cancers.