PhD Exit Seminar- Mithunah Krishnamoorthy – Tuesday, January 16, 2018

PhD Exit Seminar

Tuesday, January 16, 2018 at 2:10 pm, SW 403 – University of Toronto at Scarborough

Mithunah Krishnamoorthy (Treanor Lab)

“The Role of Novel Ion Channel TRPM7 in B Cell Development and Function”

Abstract

The channel-kinase Transient Receptor Potential Subfamily M7 (TRPM7) is known to regulate magnesium homeostasis and was first channel implicated in the survival of a B cell line. Our study is the first to show that B cells require TRPM7 for development in a murine model. By using a mouse model where TRPM7 is specifically deleted in B cells under the control of the mb1 promotor, we show that B cells are absent in all peripheral lymphoid tissues due to apoptosis of pre B cells. By using an in vitro stromal cell line system, we demonstrate that B cell development can be partially rescued by high levels of extracellular magnesium. Interestingly, the lack of B cells is accompanied by an expanded granulocyte population in the spleen. In addition to identifying TRPM7 as an essential factor for B cell development, we show that TRPM7 is also an important regulator of B cell activation. DT40 B cells lacking TRPM7 fail to contract and gather antigen when activated. To investigate the role of the kinase domain of TRPM7 we made use of B cells expressing a kinase dead point mutant. These cells were also unable to gather antigen, showing that the kinase domain is an important regulator of this process. We also show that the kinase domain may potentially interact with another important regulator of B cell activation, PLCγ2 to mediate antigen collection and cell contraction. Importantly, primary murine B cells expressing only one allele of TRPM7 or treated with a TRPM7 inhibitor both displayed defects in antigen gathering, confirming our results in the DT40 cell line. Lastly, we show that TRPM7 is essential for antigen internalization, a process that is important for the recruitment of T cell help and ultimately, antibody production.