Biology subjects

Kittisopikul, M.

Publications and source records attributed to Kittisopikul, M..

8 recordsLinked to original sources

bioRxiv2024

Periodic ER-plasma membrane junctions support long-range Ca2+ signal integration in dendrites

Neuronal dendrites must relay synaptic inputs over long distances, but the mechanisms by which activity-evoked intracellular signals propagate over macroscopic distances remain unclear. Here, we discovered a system of periodically arranged endoplasmic reticulum-plasma membrane (ER-PM) junctions tiling the plasma membrane of dendrites at [~]1 m intervals, interlinked by a meshwork of ER tubules patterned in a ladder-like array. Populated with Junctophilin-linked plasma membrane voltage-gated Ca2+ channels and ER Ca2+-release channels (ryanodine receptors), ER-PM junctions are hubs for ER-PM crosstalk, fine-tuning of Ca2+ homeostasis, and local activation of the Ca2+/calmodulin-dependent protein kinase II. Local spine stimulation activates the Ca2+ modulatory machinery facilitating voltage-independent signal transmission and ryanodine receptor-dependent Ca2+ release at ER-PM junctions over 20 m away. Thus, interconnected ER-PM junctions support signal propagation and Ca2+ release from the spine-adjacent ER. The capacity of this subcellular architecture to modify both local and distant membrane-proximal biochemistry potentially contributes to dendritic computations. HighlightsO_LIPeriodic ER-PM junctions tile neuronal dendritic plasma membrane in rodent and fly. C_LIO_LIER-PM junctions are populated by ER tethering and Ca2+ release and influx machinery. C_LIO_LIER-PM junctions act as sites for local activation of CaMKII. C_LIO_LILocal spine activation drives Ca2+ release from RyRs at ER-PM junctions over 20 m. C_LI

neuroscience↗

bioRxiv2022

Gigaxonin is required for intermediate filament transport

Gigaxonin is an adaptor protein for E3 ubiquitin ligase substrates. It is necessary for ubiquitination and degradation of intermediate filament (IF) proteins. Giant axonal neuropathy is a pathological condition caused by mutations in the GAN gene that encodes gigaxonin. This condition is characterized by abnormal accumulation of IFs in both neuronal and non-neuronal cells; however, it is unclear what causes IF aggregation. In this work, we studied the dynamics of IFs using their subunits tagged with a photoconvertible protein mEOS 3.2. We have demonstrated that the loss of gigaxonin dramatically inhibited transport of IFs along microtubules by the microtubule motor kinesin-1. This inhibition was specific for IFs, as other kinesin-1 cargoes, with the exception of mitochondria, were transported normally. Another effect of gigaxonin loss was a more than 20-fold increase in the amount of soluble vimentin oligomers in the cytoplasm of gigaxonin knock-out cells. We speculate that these oligomers saturate a yet unidentified adapter that is required for kinesin-1 binding to IFs, which might inhibit IF transport along microtubules causing their abnormal accumulation.

cell biology↗

bioRxiv2020

Nuclear Lamins A/C and B1 Provide a Structural Framework That Organizes and Anchors Nuclear Pore Complexes

Nuclear lamin isoforms form fibrous meshworks associated with nuclear pore complexes (NPCs). Using data sets prepared from sub-pixel and segmentation analyses of 3D-Structured Illumination Microscopy images of WT and lamin isoform knockout mouse embryo fibroblasts, we determined with high precision the spatial association of NPCs with specific lamin isoform fibers. These relationships are retained in the enlarged lamin meshworks of Lmna-/- and Lmnb1-/- fibroblast nuclei. Cryo-ET observations reveal that the lamin filaments composing the fibers contact the nucleoplasmic ring of NPCs. Knockdown of the ring-associated nucleoporin ELYS induces NPC clusters that exclude lamin A/C fibers, but include LB1 and LB2 fibers. Knockdown of the nucleoporins TPR or NUP153 alter the arrangement of lamin fibers and NPCs. Evidence that the number of NPCs is regulated by specific lamin isoforms is presented. Overall the results demonstrate that lamin isoforms and nucleoporins act together to maintain the normal organization of lamin meshworks and NPCs within the nuclear envelope.

cell biology↗

bioRxiv2019

Community Standards for Open Cell Migration Data

Cell migration research has become a high-content field. However, the quantitative information encapsulated in these complex and high-dimensional datasets is not fully exploited due to the diversity of experimental protocols and non-standardised output formats. In addition, typically the datasets are not open for reuse. Making the data open and Findable, Accessible, Interoperable, and Reusable (FAIR) will enable meta-analysis, data integration, and data mining. Standardised data formats and controlled vocabularies are essential for building a suitable infrastructure for that purpose but are not available in the cell migration domain. We here present standardisation efforts by the Cell Migration Standardisation Organization, CMSO, an open community-driven organisation to facilitate the development of standards for cell migration data. This work will foster the development of improved algorithms and tools, and enable secondary analysis of public datasets, ultimately unlocking new knowledge of the complex biological process of cell migration.

bioinformatics↗

bioRxiv2019

Single-molecule study of the dynamic organization of Vascular Endothelial Growth Factor Receptor 2 on the endothelial cell surface

The nanoscale organization of cell surface receptors plays an important role in signaling. We determined this organization and its relation to receptor activation for VEGF Receptor-2 (VEGFR-2), a critical receptor tyrosine kinase in endothelial cells (ECs), by combining live-cell single-molecule imaging of endogenous VEGFR-2 with rigorous computational analysis. We found that surface VEGFR-2 can be mobile or immobile/confined, and monomeric or non-monomeric, with a complex interplay between the two. The mobility and interaction heterogeneity of VEGFR-2 in the basal state led to heterogeneity in the sequence of steps leading to VEGFR-2 activation by VEGF. Specifically, we found that VEGF can bind to both monomeric and non-monomeric VEGFR-2, and, when binding to monomeric VEGFR-2, promotes dimer formation but only for immobile/confined receptors. Overall, our study highlights the dynamic and heterogeneous nature of cell surface receptor organization and its complex relationships with receptor activation and signaling.

biophysics↗

bioRxiv2019

Adaptive-Resolution Multi-Orientation Analysis of Complex Filamentous Network Images

Microscopy images of cytoskeletal, nucleoskeletal, and other filamentous structures contain complex junctions where multiple filaments with distinct orientations overlap, yet state-of-the-art software generally uses single orientation analysis to segment these structures. We describe an image analysis approach to simultaneously segment both filamentous structures and their intersections in microscopy images, based on analytically resolving coincident multiple orientations upon image filtering in a manner that balances orientation resolution and spatial localization.

bioinformatics↗

bioRxiv2019

NETosis proceeds by cytoskeleton and endomembrane disassembly and PAD4-mediated chromatin de-condensation and nuclear envelope rupture

Neutrophil extracellular traps (NETs) are web-like DNA structures decorated with histones and cytotoxic proteins that are released by activated neutrophils to trap and neutralize pathogens during the innate immune response, but also form in and exacerbate sterile inflammation. Peptidylarginine deiminase 4 (PAD4) citrullinates histones and is required for NET formation (NETosis) in mouse neutrophils. While the in vivo impact of NETs is accumulating, the cellular events driving NETosis and the role of PAD4 in these events are unclear. We performed high resolution time-lapse microscopy of mouse and human neutrophils (PMN) and differentiated HL-60 neutrophil-like cells (dHL-60) labelled with fluorescent markers of organelles and stimulated with ionomycin or lipopolysaccharides to induce NETosis. Upon stimulation, cells exhibited rapid disassembly of the actin cytoskeleton, followed by shedding of plasma membrane microvesicles, disassembly and remodeling of the microtubule and vimentin cytoskeletons, ER vesiculation, chromatin de-condensation and nuclear rounding, progressive plasma membrane and nuclear envelope (NE) permeabilization, nuclear lamin meshwork and then NE rupture to release DNA into the cytoplasm, and finally plasma membrane rupture and discharge of extracellular DNA. Inhibition of actin disassembly blocked NET release. Mouse and dHL-60 cells bearing genetic alteration of PAD4 showed that chromatin de-condensation, lamin meshwork and NE rupture and extracellular DNA release required the enzymatic and nuclear localization activities of PAD4. Thus, NETosis proceeds by a step-wise sequence of cellular events culminating in the PAD4-mediated expulsion of DNA.\n\nSignificance StatementNeutrophils are white blood cells specialized as the first line of host defense in the immune system. One way they protect organisms is through NETosis, in which they expel their DNA to form a web-like trap that ensnares pathogens and promotes clotting. However, NETs also mediate sterile inflammation, causing damage to the body. We used high-resolution live-cell microscopy to perform the first systematic characterization of the timing of dynamic cellular events leading to NETosis in human and mouse neutrophils and a neutrophil-like cell line. We discovered that NETosis proceeds by a step-wise sequence of cellular events that is conserved across species, and requires the activity of the PAD4 enzyme for DNA to be released from the nucleus and cell membrane.

immunology↗

bioRxiv2018

Universal Light-Sheet Generation with Field Synthesis

We introduce Field Synthesis, a theorem that can be used to synthesize any scanned or dithered light-sheet, including those used in lattice light-sheet microscopy (LLSM), from an incoherent superposition of one-dimensional intensity distributions. This user-friendly and modular approach offers a drastically simplified optical design, higher light-throughput, simultaneous multicolor illumination, and a 100% spatial duty cycle, thereby providing uncompromised biological imaging with decreased rates of photobleaching.

bioengineering↗