A genome wide CRISPR screen reveals novel determinants of long-lived plasma cell secretory capacity

Plasma cell subsets vary in their lifespans and ability to sustain humoral immunity. We conducted a genome-wide CRISPR-Cas9 screen in myeloma cells for factors that promote surface expression of CD98, a marker of longevity in mouse plasma cells. A large fraction of genes found to promote CD98 expression in this screen are involved in secretory and other vesicles, including subunits of the V-type ATPase complex. Genetic ablation and chemical inhibition of V-type ATPases in myeloma cells and primary plasma cells, respectively, reduced antibody secretion. Mouse and human long-lived plasma cells had greater numbers of acidified vesicles than their short-lived counterparts, and this correlated with increased antibody secretory capacity. The screen also revealed a requirement for the signaling adapter MYD88 in CD98 expression. Plasma cell-specific deletion of Myd88 led to reduced survival and antibody secretion by antigen-specific cells in vivo and unresponsiveness to BAFF and APRIL ex vivo. These data reveal novel regulators that link plasma cell secretory capacity and lifespan. SummaryLong-lived plasma cells rely on V-type ATPases, PI4K, DDX3X, and MYD88 signals for maximal secretory capacity and survival