High-resolution CRISPR/Cas9 screens identify PAK2 as a suppressor of macrophage proliferation and macropinocytosis.

ABSTRACT: Macrophages play critical roles in immune function and are implicated as etiological agents in disease states such as cardiovascular disease and cancer. However, there is limited understanding of macrophage fitness molecular regulators, including survival, proliferation, and adhesion. This work identifies positive and negative regulators of macrophage fitness by harnessing the power of CRISPR/Cas9 whole genome screening technology. Here, we identified loss-of-function gene disruptions that caused mutant bone marrow-derived macrophages (BMDM) to decrease in culture abundance as supporters of macrophage fitness. Similarly, we identified genes that limit or suppress macrophage fitness by identifying those gene disruptions that caused BMDM to increase in abundance in cell culture. To do this, we analyzed the difference in frequency of sgRNA between the purified plasmid library used for lentiviral transfection versus the amplified sgRNA inserts from the DNA of BMDM following a 14-day post-viral transduction culture. With this approach, we identified gene disruptions to canonical essential genes, including previously described macrophage-specific essential genes such as Csf1r, as well as novel genes required for macrophage growth and survival. In addition, we also identified gene disruptions that increased macrophage abundance in culture, including canonical tumor suppressors such as p53 (Trp53) and cell cycle regulators (Cdkn1a/2a). Interestingly, targeting p21-activated kinase-2 (Pak2) led to those mutants becoming more productive, suggesting a novel role for Pak2 in suppressing macrophage fitness. Using targeted knockouts of PAK2, we show that PAK2 protein depletion affects NF2/Merlin-mediated downregulation of cyclin-d1. Further, this work indicates that PAK2 suppresses macropinocytic uptake in macrophages by modulating actin dynamics impacting pro-mitogenic signaling pathways downstream of macropinocytosis. Overall, this work shows how multiple pathways impact macrophage fitness and highlights the central role of PAK2 in macrophage fitness and macropinocytosis.

ORGANISM(S): Mus musculus

PROVIDER: GSE251887 | GEO | 2024/05/01

REPOSITORIES: GEO