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Remodelling of cortical actin where lytic granules dock at natural killer cell immune synapses revealed by super-resolution microscopy
- Source :
- PLoS Biology, Vol 9, Iss 9, p e1001152 (2011), PLoS Biology
- Publication Year :
- 2011
- Publisher :
- Public Library of Science (PLoS), 2011.
-
Abstract
- Super-resolution 3D imaging reveals remodeling of the cortical actin meshwork at the natural killer cell immune synapse, which is likely to be important for secretion of lytic granules.<br />Natural Killer (NK) cells are innate immune cells that secrete lytic granules to directly kill virus-infected or transformed cells across an immune synapse. However, a major gap in understanding this process is in establishing how lytic granules pass through the mesh of cortical actin known to underlie the NK cell membrane. Research has been hampered by the resolution of conventional light microscopy, which is too low to resolve cortical actin during lytic granule secretion. Here we use two high-resolution imaging techniques to probe the synaptic organisation of NK cell receptors and filamentous (F)-actin. A combination of optical tweezers and live cell confocal microscopy reveals that microclusters of NKG2D assemble into a ring-shaped structure at the centre of intercellular synapses, where Vav1 and Grb2 also accumulate. Within this ring-shaped organisation of NK cell proteins, lytic granules accumulate for secretion. Using 3D-structured illumination microscopy (3D-SIM) to gain super-resolution of ∼100 nm, cortical actin was detected in a central region of the NK cell synapse irrespective of whether activating or inhibitory signals dominate. Strikingly, the periodicity of the cortical actin mesh increased in specific domains at the synapse when the NK cell was activated. Two-colour super-resolution imaging revealed that lytic granules docked precisely in these domains which were also proximal to where the microtubule-organising centre (MTOC) polarised. Together, these data demonstrate that remodelling of the cortical actin mesh occurs at the central region of the cytolytic NK cell immune synapse. This is likely to occur for other types of cell secretion and also emphasises the importance of emerging super-resolution imaging technology for revealing new biology.<br />Author Summary Natural Killer (NK) cells are immune cells that can recognise and kill virus-infected and cancerous cells. This killing requires an intercellular contact —termed an immune synapse—between the NK cell and its target cell through which molecules can be delivered to trigger lysis. Reorganisation of the NK cell cytoskeleton is essential for the delivery and release at the synapse of granules containing the cytolytic molecules. Understanding precisely how the cytoskeleton is involved in these cytolytic events has been hampered by our inability to resolve cytoskeletal structure at immune synapses by conventional light microscopy. Very recent advances in imaging technology have now provided the resolving power to see previously undetectable cellular structures. Here, we have used 3D super-resolution imaging to observe the structure of the actin cytoskeleton at the NK immune synapse. We found that a dense mesh of actin underlies the immune synapse and that it is remodelled upon NK cell activation. Domains within the actin meshwork open up specifying where the lytic granules dock and also where the microtubule-organising centre moves towards. Thus, actin remodelling occurs at the immune synapse during secretion and this may be important for the regulation of lytic granule secretion.
- Subjects :
- Life Sciences & Biomedicine - Other Topics
IMMUNOLOGICAL SYNAPSE
Immunological Synapses
Optical Tweezers
STRUCTURED-ILLUMINATION MICROSCOPY
NK cells
Lymphocyte Activation
Cell Degranulation
Immunological synapse
Cell membrane
Actin remodeling of neurons
0302 clinical medicine
Cell polarity
Image Processing, Computer-Assisted
Biology (General)
11 Medical and Health Sciences
RECEPTOR MICROCLUSTERS
0303 health sciences
Microscopy, Confocal
Secretory Pathway
MYOSIN-IIA
General Neuroscience
Immune cells
SECRETORY DOMAIN
Intercellular Adhesion Molecule-1
CYTOLYTIC INTERACTIONS
Lymphocyte Function-Associated Antigen-1
Cell biology
Killer Cells, Natural
medicine.anatomical_structure
Lytic cycle
NK Cell Lectin-Like Receptor Subfamily K
General Agricultural and Biological Sciences
Life Sciences & Biomedicine
Research Article
Plasmids
Biochemistry & Molecular Biology
QH301-705.5
Immunology
Primary Cell Culture
chemical and pharmacologic phenomena
Biology
Transfection
General Biochemistry, Genetics and Molecular Biology
Natural killer cell
Cell Line
03 medical and health sciences
07 Agricultural and Veterinary Sciences
medicine
HUMAN NK CELLS
Humans
030304 developmental biology
GRB2 Adaptor Protein
Science & Technology
General Immunology and Microbiology
INHIBITORY RECEPTORS
06 Biological Sciences
NKG2D
Image Enhancement
Actins
T-CELLS
TARGET-CELLS
Microtubule-Organizing Center
030215 immunology
Developmental Biology
Subjects
Details
- Language :
- English
- ISSN :
- 15457885 and 15449173
- Volume :
- 9
- Issue :
- 9
- Database :
- OpenAIRE
- Journal :
- PLoS Biology
- Accession number :
- edsair.doi.dedup.....3a94295134b3a938d7419acceec7e298