Membrane-cytoskeletal crosstalk mediated by myosin-I regulates adhesion turnover during phagocytosis

Abstract

Phagocytosis of invading pathogens or cellular debris requires a dramatic change in cell shape driven by actin polymerization. For antibody-covered targets, phagocytosis is thought to proceed through the sequential engagement of Fc-receptors on the phagocyte with antibodies on the target surface, leading to the extension and closure of the phagocytic cup around the target. We find that two actin-dependent molecular motors, class 1 myosins myosin 1e and myosin 1f, are specifically localized to Fc-receptor adhesions and required for efficient phagocytosis of antibody-opsonized targets. Using primary macrophages lacking both myosin 1e and myosin 1f, we find that without the actin-membrane linkage mediated by these myosins, the organization of individual adhesions is compromised, leading to excessive actin polymerization, slower adhesion turnover, and deficient phagocytic internalization. This work identifies a role for class 1 myosins in coordinated adhesion turnover during phagocytosis and supports a mechanism involving membrane-cytoskeletal crosstalk for phagocytic cup closure.

Combined Atomic Force Microscope and Volumetric Light Sheet System for Mechanobiology

“…5c and Supplementary Videos 5 & 6, an x-y plane maximum intensity projection of the image data in the volume of the cup showed actin accumulations, spaced ~1.5 µm from each other, at the base of the bead. These podosome-like structures 29 are consistent with observations reported by Barger et al 36 in their study investigating the interplay between myosin-I and actin structure in the phagocytic cup. In the future we will perform 3D correlation analysis to understand the role of these structures in force generation on target cells.…”

Spatio-temporal mapping of mechanical force generated by macrophages during FcγR-dependent phagocytosis reveals adaptation to target stiffness

“…A possible candidate could be the Myosin I family. Indeed, Myosin IE,F,G all connect the membrane to the cytoskeleton, are present at the phagocytic cup and have been shown to participate in target engulfment (Barger et al 2019, Dart et al 2012. Alternatively, the presence of adhesive integrins and podosome-like structures may also contribute to mechano-signaling (Maxson et al 2018, Ostrowski et al 2019.…”

iASPP contributes to cortex rigidity, astral microtubule capture and mitotic spindle positioning

“…As ERM knockdown HeLa cells do not display the spindle defects or lack of cell rounding 10 , it was suggested that additional cross-linkers play a role in cortical stability in mammalian cells. Class I myosins, including Myo1c, which similarly to ERM proteins connect the plasma membrane to the underlying actin cytoskeleton, are important regulators of membrane tension and cell stiffness in brush border cells, primary mouse fibroblasts and macrophages [45][46][47] . Our observations demonstrate that Myo1c contributes to cortical stiffness of mitotic HeLa; recent studies indicate that effective stiffness is directly related to cortical tension 48,49 .…”