B cells play a central role in human health by protecting us against infections through their ability to produce high-affinity antibodies and long-lived memory cells capable of antigenic recall. Perturbations in B cell function can not only lead to lowered ability to fight infections and inefficacy of vaccinations, but also to conditions such as leukemia, and autoimmune diseases. Thus, understanding the molecular mechanisms that contribute to optimal B cell function is extremely important for the generation of new therapeutics and vaccination strategies. The major goal of this proposal is to study how autophagy, a lysosomal degradative pathway with numerous physiological and pathophysiological roles, shapes B cell immunoresponses. The induction of canonical autophagy typically requires the downregulation of the biosynthetic kinase, mTORC1. However, in B cells upon BCR stimulation both autophagy and mTORC1 activity are simultaneously upregulated, suggesting that B cell autophagy is likely to be mTORC1 independent. Our lab has recently shown that there is a switch from basal canonical autophagy in nave, antigen-inexperienced B cells to an unconventional, mTORC1-independent, non- canonical activity in the germinal center (GC) B cells upon antigenic stimulation. GCs are the determinants of high affinity, class switched antibody generation, and therefore the study of the mechanisms that drive these high-quality immunoresponses is vitally important in the development of next-generation vaccines, therapeutic monoclonal antibodies and in the treatment of autoimmune diseases. Our working hypothesis is that non-canonical autophagy is important during B cell proliferation and will be relevant to GC biology affecting antibody quality, while canonical autophagy is important for long-lived memory cells and plasma cells influencing antibody durability. To test this hypothesis, we will evaluate GC and long-term immune responses in mice bearing genetic ablations of novel autophagy genes that we know affect the balance between canonical and non-canonical autophagy, namely Wipi1, Wipi2 and Rubicon. We will also determine the mechanisms by which the deletions of these genes affect antigen presentation and in eliciting T cell help. Finally, because autophagy intersects with mitochondrial integrity and metabolism, we will determine how these gene deletions control the capacity of GC B cells, memory and plasma cells to regulate ROS production, mitochondrial homeostasis and metabolic status and potentially influence B cell fate. We envision that the successful completion of these experimental aims will not only provide a better understanding of B cell function, but also mechanistic insights into how to modulate autophagy to affect humoral immunity ? augment it in cases such as immunosenescence, or downregulate it in instances of autoimmune diseases.
The immune system defends the body by making antibodies that recognize and destroy infectious agents. The impairment of one of the immune components, B cells, can result in the overgrowth of pathogens, lingering infections or autoimmune diseases. Our proposal investigates the role of autophagy, a universally conserved protein degradation process in regulating optimal B cell function.
|Tsui, Carlson; Maldonado, Paula; Montaner, Beatriz et al. (2018) Dynamic reorganisation of intermediate filaments coordinates early B-cell activation. Life Sci Alliance 1:e201800060|