The Role of Extracellular Vesicles in B Cell Development and Function

The Role of Extracellular Vesicles in B Cell Development and Function

Hong-Dien Phan

Ph.D. Student

Department of Biochemistry

Date: Monday, February 14, 2022

Time: 1 - 2 pm

Location: Arts Building Room 1046

Abstract

Extracellular vesicles (EVs) are membrane-encapsulated nanosized particles that carry bioactive cargo, including proteins, nucleic acids, and lipids. EVs are secreted by most living cells, including B lymphocytes (B cells). B cells are antibody-producing immune cells that develop in the bone marrow, where many different cell surface receptors regulate their maturation. One of the earliest surface proteins expressed in developing B cells is called CD24, a glycophosphatidylinositol (GPI)-linked to protein localized to lipid rafts on the cell plasma membrane. Past research in the Christian lab showed that engagement of CD24 on the immature murine WEHI-231 B lymphoma cell line could cause the release of bioactive EVs. Following in the footsteps of the first discovery, we employed a model system where donor cells expressing palmitoylated GFP (WEHI-231-GFP) were co-cultured, after stimulation, with recipient cells lacking either IgM (WEHI-303 murine B cells) or CD24 (CD24 knock-out mouse bone marrow B cells). We next found that EV trafficking of lipid and membrane proteins between B cells in response to stimulation of either CD24 or IgM on the donor cells. Importantly, we found that EV-mediated transfer of CD24 or BCR may affect B cell development by inducing apoptosis in recipient bystander cells. The data from this study and our previous studies suggests that the EVs induced by CD24 stimulation are microvesicles (MVs) budded off the plasma membrane and not exosomes derived from multi-vesicular bodies. However, the underlying mechanisms that govern MV formation in response to engagement of CD24 remain mostly elusive. Thus, my future work will elucidate how CD24 regulates MVs releases.