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Filopodia are thin, actin-based structures that cells use to interact with their environments. Filopodia initiation requires a suite of conserved proteins but the mechanism remains poorly understood. The actin polymerase VASP and a MyTH-FERM (MF) myosin, DdMyo7 in amoeba, are essential for filopodia initiation. DdMyo7 is localized to dynamic regions of the actin-rich cortex. Analysis of VASP mutants and treatment of cells with anti-actin drugs shows that myosin recruitment and activation in requires localized VASP-dependent actin polymerization. Targeting of DdMyo7 to the cortex alone is not sufficient for filopodia initiation; VASP activity is also required. The actin regulator locally produces a cortical actin network that activates myosin and together they shape the actin network to promote extension of parallel bundles of actin during filopodia formation. This work reveals how filopodia initiation requires close collaboration between an actin-binding protein, the state of the actin cytoskeleton and MF myosin activity.
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http://dx.doi.org/10.7554/eLife.68082 | DOI Listing |
Fish Shellfish Immunol
September 2025
Liaoning Key Laboratory of Marine Animal Immunology and Disease Control, Dalian Ocean University, Dalian, 116023, China; Laboratory of Marine Fisheries Science and Food Production Process, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266235, China; Liaoning Key Laboratory
The primitive innate immune cells (termed haemocytes) initially evolved in molluscs, which are analogous to vertebrate leukocytes, displaying significant morphological and functional heterogeneity. Elucidating the diversity morphology and functions of haemocytes is crucial to understanding the ancient immune system. In the present study, six novel haemocyte subtypes, including pro-haemocytes, larger agranulocytes, secretory haemocytes, amoeba phagocytes, macrophages and dendritic (DC)-like haemocytes were identified by their specific morphological and functional characteristics in oyster circulating haemolymph.
View Article and Find Full Text PDFFront Cell Infect Microbiol
September 2025
Multiuser Laboratory of Cell Biology and Ultrastructure, Evandro Chagas Institute, Belém, Pará, Brazil.
Background: The protozoan , in addition to infecting phagocytic cells such as macrophages, can also invade non-professional phagocytic cells like fibroblasts, a process previously described in 2D models. In a bidimensional environment, its interaction with the extracellular matrix and manipulation of endocytic processes reveal a complex ability to alter cellular entry mechanisms. However, this process in fibroblasts, especially in three-dimensional (3D) models, remains poorly understood.
View Article and Find Full Text PDFJ Cell Sci
September 2025
Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, 7610001 Israel.
Secretory granules are specialized vesicles that package large amounts of cargo, such as hormones, enzymes and mucous. They are typically stored intracellularly until an extracellular signal initiates exocytosis, characterized by fusion between the secretory vesicles and the plasma membrane, resulting in cargo release to the environment. Observations made in the 1970s suggested that some secretory granules project a pseudopodium from their surface where fusion with the cell surface occurs.
View Article and Find Full Text PDFNat Commun
July 2025
Conway Institute, School of Medicine, University College Dublin, Dublin, Ireland.
Well-organized repair of damaged barrier epithelia is vital for infection control, resolution of inflammation, and enduring physical protection. Cysteine thiol and methionine oxidation are connected to cytoskeletal rearrangements in cell migration and wound healing, but how localized redox signaling is achieved to regulate dynamic processes remains elusive. Here, we identify DUOX2, a mucosal barrier NADPH oxidase, as vesicle-incorporated HO source, localizing to sites of cytoskeletal reorganization, and facilitating tunneling nanotube and lamellipodia formation.
View Article and Find Full Text PDFJ Extracell Vesicles
June 2025
Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden.
Extracellular vesicles derived from gram-negative bacteria are nano-sized particles of different size and origin released by these microbes and are collectively called bacterial extracellular vesicles (BEVs). These BEVs may serve as vehicles for delivering bacterial molecules to eukaryotic host cells. Depending on the bacterial species, BEVs elicit various host cellular and immunomodulatory responses, often aiding bacterial survival and communication.
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