PhD Transfer Examination – Trisha Mahtani (Treanor lab)

PhD Transfer Exam

Friday January 27^th, 3:10 pm – Room SW 403, University of Toronto at Scarborough

Trisha Mahtani (Treanor lab)

“The role of TRPV5 in B cell activation and signaling“

Abstract

B cells are the precursors to plasma cells which secrete antibodies that target foreign pathogen (antigen) within the body. This differentiation into plasma cells and antibody secretion begins with the activation of B cells through binding of B cell receptor (BCR) to specific antigen, which leads to formation of BCR clusters and initiation of downstream signaling cascades. One of the key second messengers is calcium, which activates many calcium dependent proteins involved in activation. Calcium ions enter the cell through ion channels on the plasma membrane, of which the best characterized are Calcium Release-Activated Calcium (CRAC) channels. However, B cells deficient in CRAC channel components mount normal antibody responses, suggesting that alternative channels may be important. Several members of the Transient Receptor Potential (TRP) ion channel family are calcium permeable, yet the function of many members of this family in the immune cell activation has not been characterized. To determine the members of the TRPV subfamily that are expressed in B cells, we performed a quantitative qPCR screen and found that TRPV2, TRPV4 and TRPV5 are expressed. TRPV5 is selectively permeable to calcium ions and has been shown to shuttle to the plasma membrane upon stimulatory cues in other cell types. We investigated whether this phenomenon occurs in B cells and found that upon BCR activation this channel polarizes to the side of the cell where BCR clusters localize. To examine whether TRPV5 is involved in calcium signaling during B cell activation, we used siRNA knockdown to reduce protein expression and found that this impaired signaling. Thus, our findings suggest that TRPV5 may play a role in the initial events of B cell signaling during activation. To further explore this novel finding, this project aims to characterize a TRPV5 knockout generated by CRISPR-Cas9. This work will help us understand the role of a novel regulator in B cell activation.