Myosin II Synergizes with F-Actin to Promote DNGR-1-Dependent Cross-Presentation of Dead Cell-Associated Antigens

Abstract

SummaryConventional type 1 DCs (cDC1s) excel at cross-presentation of dead cell-associated antigens partly because they express DNGR-1, a receptor that recognizes exposed actin filaments on dead cells. In vitro polymerized F-actin can be used as a synthetic ligand for DNGR-1. However, cellular F-actin is decorated with actin-binding proteins, which could affect DNGR-1 recognition. Here, we demonstrate that myosin II, an F-actin-associated motor protein, greatly potentiates the binding of DNGR-1 to F-actin. Latex beads coated with F-actin and myosin II are taken up by DNGR-1+ cDC1s, and antigen associated with those beads is efficiently cross-presented to CD8+ T cells. Myosin II-deficient necrotic cells are impaired in their ability to stimulate DNGR-1 or to serve as substrates for cDC1 cross-presentation to CD8+ T cells. These results provide insights into the nature of the DNGR-1 ligand and have implications for understanding immune responses to cell-associated antigens and for vaccine design.

C-Type Lectin-Like Receptors: Head or Tail in Cell Death Immunity

“…However, CLEC9A diverts phagocytosed dead cell cargo to a non-degradative recycling endosome compartment thereby facilitating cross-presentation of the dead-cell-associated antigens to CD8 + T cells (23). Myosin II, an actin-associated motor protein, potentiates the binding of CLEC9A to Factin by facilitating co-operative binding of the two CTLD domains of the CLEC9A dimer, thereby rendering the crosspresentation more efficient (128). Thus, CLEC9A plays an important function in CD8 + T cell cross-priming during herpes virus infection (127,129) and specifically induces optimal generation of tissue-resident memory T cells during influenza infection (130).…”

DNGR-1, a Dendritic Cell-Specific Sensor of Tissue Damage That Dually Modulates Immunity and Inflammation

“…Targeting of antigens to DNGR-1 using antibodies allows for specific delivery to cDC1s (10,13,21), which excel at cross-presentation (22), resulting in improved cross-priming of CD8 + T cells when administered under the cover of an adjuvant (10). Alternatively, specific peptides selected by in vitro evolution systems and beads coated with a synthetic F-actin/myosin II complex can be used for in vivo targeting of antigens toward DNGR-1 (23,24). Moreover, anti-DNGR-1 antibodies can be used to deliver antigen-containing nanoemulsions with immunostimulatory properties (25).…”

“…Electron cryomicroscopy of F-actin complexed with the dimeric extracellular domain of DNGR-1 shows that, in fact, only one subunit of DNGR-1 dimers is stabilized on a site on F-actin that involves three actin subunits: two consecutive subunits from the same protofilament and one from the neighboring protofilament (4). Of note, myosin II, an F-actin-associated motor protein, potentiates the binding of dimeric DNGR-1 to F-actin, explaining why F-actin from cell lysates binds more efficiently to DNGR-1 dimers than in vitro polymerized F-actin (24). A likely explanation for the increased affinity may be the spatial disposition of F-actin filaments promoted by myosin II, which might facilitate the engagement of both DNGR-1 dimer subunits to adjacent, aligned F-actin filaments.…”

C‐type lectin receptors of the Dectin‐1 cluster: Physiological roles and involvement in disease

“…CLEC‐9A (DNGR‐1) is an endocytic receptor which recognises dead cells through exposed F‐actin, a process which is enhanced by myosin II . In humans, CLEC‐9A is expressed on immature BDCA3+ DCs and on a small subset on CD14+CD16‐ monocytes, and in the mouse, on CD8α+ conventional DC and plasmacytoid DCs.…”