The mechanisms of dynamin-actin interaction

Abstract

Cell-cell fusion is an indispensable process in the conception, development and physiology of multicellular organisms. Here we demonstrate a direct and noncanonical role for dynamin, best known as a fission GTPase in endocytosis, in cell-cell fusion. Our genetic and cell biological analyses show that dynamin colocalizes within the F-actin-enriched podosome-like structures at the fusogenic synapse, which is required for generating invasive membrane protrusions and myoblast fusion in vivo, in an endocytosis-independent manner. Biochemical, negative stain EM and cryo-electron tomography (cryo-ET) analyses revealed that dynamin forms helices that directly bundles actin filaments by capturing multiple actin filaments at their outer rim via interactions with dynamin's proline-rich domain.GTP hydrolysis by dynamin triggers disassembly of the dynamin helix, exposes the sides of the actin filaments, promotes dynamic Arp2/3-mediated branched actin polymerization, and generates a mechanically stiff actin network. Thus, dynamin functions as a unique actin-bundling protein that enhances mechanical force generation by the F-actin network in a GTPase-dependent manner. Our findings have universal implications for understanding dynamin-actin interactions in various cellular processes beyond cell-cell fusion. 3Cell-cell fusion is essential for the conception, development, regeneration and physiology of multicellular organisms 1-3 . A common theme underlying cell-cell fusion events ranging from insects to mammals is the presence of actin-propelled invasive protrusions at the site of fusion, known as the fusogenic synapse 4-8 . Such invasive protrusions were first identified as part of an F-actin-enriched podosome-like structure (PLS) in Drosophila myoblast fusion 7 . The PLS is generated by an "attacking" fusion partner, the fusion-competent myoblast (FCM), which drills multiple invasive protrusions into the "receiving" fusion partner, the muscle founder cell, to promote cell membrane juxtaposition and fusion pore formation 7,9,10 . Although each protrusion has a diameter similar to that of a filopodium, these protrusions are mechanically stiffer and are capable of triggering mechanosensitive responses in the receiving cell 11 . Mechanoresponsive accumulations of myosin II and spectrin in the receiving cell, in turn, increase the cortical tension of the receiving cell, thus generating resisting forces against the invasive protrusions and bringing the two cell membranes to close proximity to promote cell fusion 11,12 .The invasive protrusions from the attacking cells are propelled by Arp2/3-mediated branched actin polymerization, which generates short actin filaments more suitable for mechanical work than long and linear filaments 9 . However, how the branched actin filaments are organized to generate mechanically stiff membrane protrusions during fusion is unknown.Dynamin (Dyn) is a large GTPase best known for its role in endocytosis. Dynamin catalyzes membrane fission by forming rings/helices around necks of a budding endocytic ve...

Recessive variants in the intergenicNOS1AP-C1orf226locus cause monogenic kidney disease responsive to anti-proteinuric treatment

“…Dynamin stimulates actin bundling and, like NOS1AP, promotes filopodia formation (20,23,(43)(44)(45). Dynamin activating compound Bis-T-23 reduced albuminuria and normalized podocyte ultrastructural defects in multiple murine podocytopathies (46).…”

Open and cut: allosteric motion and membrane fission by dynamin superfamily proteins

“…They play critical roles in organelle homeostasis and as innate immunity effectors that restrict certain pathogens (Bui and Shaw, 2013; Haller et al , 2015). Independent of their membrane binding activity, DSPs also play an increasingly appreciated role as regulators and organizers of both the actin- and microtubule-based cytoskeleta (Strack et al , 2013; Hatch et al , 2014; Zhang et al , 2019).…”

The host GTPase Dynamin 2 modulates apical junction structure to control cell-to-cell spread ofListeria monocytogenes

“…The three Dynamin proteins exhibit GTPdependent membrane fission activity, which is critical for their endocytic roles (19). In addition to stimulating membrane fission, Dynamin proteins use their GTPase activity to regulate the actin cytoskeleton (18,26,27). This cytoskeletal function contributes to endocytosis (26) and also controls cell migration (28), myoblast formation (27), tight junction structure (29)(30)(31), and the generation of protrusive structures such as podosomes (32)(33)(34)(35), dendritic spines (36), and axonal growth cones (37,38).…”

“…Dynamin GTPases are recruited to the plasma membrane by interaction of their PRD with SH3 domains in various proteins that contain BAR (Bin-Amphiphysin-Rvs) domains (39,40). Dynamin proteins then oligomerize, resulting in stimulation of GTP hydrolysis and consequent conformational changes that promote membrane fission or actin polymerization (19,26,27).…”