PDGFA-associated protein 1 protects mature B lymphocytes from stress-induced cell death and promotes antibody gene diversification
Verónica Delgado-Benito, Maria Berruezo-Llacuna, Robert Altwasser, Wiebke Winkler, Devakumar Sundaravinayagam, Sandhya Balasubramanian, Marieta Cagánová, Robin Graf, Ali Rahjouei, Marie‐Thérèse Henke, Madlen Driesner, Lisa Keller, Alessandro Prigione, Martin Janz, Altuna Akalin, Michela Di Virgilio
Abstract
The establishment of protective humoral immunity is dependent on the ability of mature B cells to undergo antibody gene diversification while adjusting to the physiological stressors induced by activation with the antigen. Mature B cells diversify their antibody genes by class switch recombination (CSR) and somatic hypermutation (SHM), which are both dependent on efficient induction of activation-induced cytidine deaminase (AID). Here, we identified PDGFA-associated protein 1 (Pdap1) as an essential regulator of cellular homeostasis in mature B cells. Pdap1 deficiency leads to sustained expression of the integrated stress response (ISR) effector activating transcription factor 4 (Atf4) and induction of the ISR transcriptional program, increased cell death, and defective AID expression. As a consequence, loss of Pdap1 reduces germinal center B cell formation and impairs CSR and SHM. Thus, Pdap1 protects mature B cells against chronic ISR activation and ensures efficient antibody diversification by promoting their survival and optimal function.