Quantification and modeling of podosomes during frustrated phagocytosis

Podosomes are complex, actin-rich cellular adhesion structures important for migration, motility, tumor invasion, and more. One system in which podosomes play a crucial role is in phagocytosis, the recognition and engulfment of small particles by cells. To observe podosome dynamics, we use the experimental system of “frustrated” phagocytosis, in which cells attempt to engulf fixed, micropatterned discs of antibody. This process is frustrated because cells can recognize the antibody and engage in signaling yet are unable to fully engulf and internalize the fixed discs of antibody. This system is advantageous for studying both the physical structure of podosomes and the highly dynamic spatiotemporal signaling that occurs during phagocytosis. Strikingly, we observe as podosomes form rosettes (puncta in a ring) around the discs. We use computational approaches, including persistent homology (a type of topological data analysis), to automatically identify podosomes and quantify their nanoarchitecture from 3D super-resolution microscopy data. Furthermore, we use reaction-diffusion models to investigate the molecular mechanisms that generate the rosette patterns formed during frustrated phagocytosis.