scholarly journals The architecture and operating mechanism of a cnidarian stinging organelle

2021 ◽  
Author(s):  
Matthew Gibson ◽  
Ahmet Karabulut ◽  
Melainia McClain ◽  
Boris Rubinstein ◽  
Sean McKinney
Keyword(s):  
Structural Complexity ◽  
Super Resolution ◽  
Operating Mechanism ◽  
Sea Anemones ◽  
Form And Function ◽  
3D Electron Microscopy ◽  
Genetic Perturbations ◽  
Resolution Imaging ◽  
The Operating Mechanism ◽  
And Function

Abstract The stingers of jellyfish, sea anemones and other cnidarians, known as nematocysts, are remarkable cellular weapons used for both predation and defense1. Nematocysts are specialized organelles which consist of a pressurized capsule containing a coiled harpoon-like thread2. These structures are in turn built within specialized cells known as nematocytes3. When triggered4, the capsule explosively discharges, ejecting the coiled thread which punctures the target and rapidly elongates by turning inside out in a process called eversion5,6. Due to the structural complexity of the thread and the extreme speed of discharge, the precise mechanics of nematocyst firing have remained elusive7. Here, using a combination of live and super-resolution imaging, 3D electron microscopy and genetic perturbations, we define the step-by-step sequence of nematocyst operation in the model sea anemone Nematostella vectensis. This analysis reveals the complex biomechanical transformations underpinning the operating mechanism of nematocysts, one of the nature’s most exquisite biological micro-machines. Further, this study will provide insight into the form and function of related cnidarian organelles and serve as a template for the design of bioinspired microdevices.

scholarly journals The architecture and operating mechanism of a cnidarian stinging organelle

2021 ◽  
Author(s):  
Ahmet Karabulut ◽  
Melainia McClain ◽  
Boris Rubinstein ◽  
Sean A. McKinney ◽  
Matthew C. Gibson
Keyword(s):  
Structural Complexity ◽  
Super Resolution ◽  
Operating Mechanism ◽  
Sea Anemones ◽  
Form And Function ◽  
3D Electron Microscopy ◽  
Genetic Perturbations ◽  
Resolution Imaging ◽  
The Operating Mechanism ◽  
And Function

AbstractThe stingers of jellyfish, sea anemones and other cnidarians, known as nematocysts, are remarkable cellular weapons used for both predation and defense1. Nematocysts are specialized organelles which consist of a pressurized capsule containing a coiled harpoon-like thread2. These structures are in turn built within specialized cells known as nematocytes3. When triggered4, the capsule explosively discharges, ejecting the coiled thread which punctures the target and rapidly elongates by turning inside out in a process called eversion5,6. Due to the structural complexity of the thread and the extreme speed of discharge, the precise mechanics of nematocyst firing have remained elusive7. Here, using a combination of live and super-resolution imaging, 3D electron microscopy and genetic perturbations, we define the step-by-step sequence of nematocyst operation in the model sea anemone Nematostella vectensis. This analysis reveals the complex biomechanical transformations underpinning the operating mechanism of nematocysts, one of the nature’s most exquisite biological micro-machines. Further, this study will provide insight into the form and function of related cnidarian organelles and serve as a template for the design of bioinspired microdevices.

scholarly journals Super-resolution imaging uncovers the nanoscopic segregation of polarity proteins in epithelia

2020 ◽  
Author(s):  
Pierre Mangeol ◽  
Dominique Massey-Harroche ◽  
Fabrice Richard ◽  
Pierre-François Lenne ◽  
André Le Bivic
Keyword(s):  
Cell Polarity ◽  
Super Resolution ◽  
Actin Organization ◽  
Resolution Imaging ◽  
Polarity Proteins ◽  
Endogenous Proteins ◽  
Apical Junctions ◽  
And Function ◽  
Potential Interactions ◽  
Nanoscale Level

AbstractEpithelial tissues acquire their integrity and function through the apico-basal polarization of their constituent cells. Proteins of the PAR and Crumbs complexes are pivotal to epithelial polarization, but the mechanistic understanding of polarization is challenging to reach, largely because numerous potential interactions between these proteins and others have been found, without clear hierarchy in importance. We identify the regionalized and segregated organization of members of the PAR and Crumbs complexes at epithelial apical junctions by imaging endogenous proteins using STED microscopy on Caco-2 cells, human and murine intestinal samples. Proteins organize in submicrometric clusters, with PAR3 overlapping with the tight junction (TJ) while PALS1-PATJ and aPKC-PAR6β form segregated clusters that are apical of the TJ and present in an alternated pattern related to actin organization. CRB3A is also apical of the TJ and weakly overlaps with other polarity proteins. This organization at the nanoscale level significantly simplifies our view on how polarity proteins could cooperate to drive and maintain cell polarity.

scholarly journals Proteomic and functional analyses of the periodic membrane skeleton in neurons

2020 ◽  
Author(s):  
Ruobo Zhou ◽  
Boran Han ◽  
Roberta Nowak ◽  
Yunzhe Lu ◽  
Evan Heller ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Adhesion Molecules ◽  
Cell Adhesion Molecules ◽  
Super Resolution ◽  
Membrane Skeleton ◽  
Interacting Proteins ◽  
Functional Roles ◽  
Genetic Perturbations ◽  
Resolution Imaging ◽  
Functional Analyses

AbstractActin, spectrin, and associated molecules form a membrane-associated periodic skeleton (MPS) in neurons. The molecular composition and functions of the MPS remain incompletely understood. Here, using co-immunoprecipitation and mass spectrometry, we identified hundreds of candidate MPS-interacting proteins that span diverse functional categories. We validated representative proteins in several of these categories, including previously unknown MPS structural components, as well as motor proteins, cell adhesion molecules, ion channels, and signaling proteins, demonstrating periodic distributions of ∼20 proteins in neurons using super-resolution imaging. Genetic perturbations of the MPS and its interacting proteins further suggested functional roles of the MPS in axon-axon and axon-dendrite interactions and in axon diameter regulation, and implicated the involvement of MPS interactions with cell adhesion molecules and non-muscle myosin in these roles. These results provide new insights into the interactome of the MPS, and suggest new functions of the MPS in neurons.

Form and function: structural analysis in evolutionary morphology

Paleobiology ◽  
1981 ◽  
Vol 7 (4) ◽  
pp. 430-442 ◽  
Author(s):  
George V. Lauder
Keyword(s):  
Structural Complexity ◽  
Morphological Diversity ◽  
Structural Features ◽  
Constrained Systems ◽  
Hierarchical Organization ◽  
Evolutionary Morphology ◽  
Form And Function ◽  
Historical Factors ◽  
Functional Patterns ◽  
And Function

A theoretical approach to the analysis of historical factors (Raup 1972) in evolutionary morphology is presented which addresses transformational hypotheses about structural systems. This (structural) approach to testing historical hypotheses about phylogenetic constraints on form and function and structural and functional versatility involves (1) the reconstruction of nested sets of structural features in monophyletic taxa, (2) the use of general or emergent organizational properties of structural and functional systems (as opposed to uniquely derived morphological features), and (3) the comparative examination of the consequences for structural and functional diversity of these general features in related monophyletic taxa.Three examples of emergent organizational properties are considered: structural complexity, repetition of parts, and the decoupling of primitively constrained systems. Two classes of hypotheses about the evolution of design are proposed. Transformational hypotheses concern historical pathways of change in form as a consequence of general organizational features which are primitive for a lineage. Relational hypotheses involve correlations between structure-function networks primitive for a clade and morphological diversity both between and within terminal taxa. To the extent that transformational and relational hypotheses about form are corroborated, they provide evidence of underlying regularity in the transformation of organic design that may be a consequence of the hierarchical organization of structural and functional patterns in organisms.

Tools and limitations to study the molecular composition of synapses by fluorescence microscopy

2016 ◽  
Vol 473 (20) ◽  
pp. 3385-3399 ◽  
Author(s):  
Manuel Maidorn ◽  
Silvio O. Rizzoli ◽  
Felipe Opazo
Keyword(s):  
Super Resolution ◽  
Molecular Composition ◽  
Synaptic Organization ◽  
Synaptic Physiology ◽  
Copy Numbers ◽  
Resolution Imaging ◽  
And Function ◽  
Microscopy Techniques ◽  
Super Resolution Microscopy ◽  
Affinity Probes

The synapse is densely packed with proteins involved in various highly regulated processes. Synaptic protein copy numbers and their stoichiometric distribution have a drastic influence on neuronal integrity and function. Therefore, the molecular analysis of synapses is a key element to understand their architecture and function. The overall structure of the synapse has been revealed with an exquisite amount of details by electron microscopy. However, the molecular composition and the localization of proteins are more easily addressed with fluorescence imaging, especially with the improved resolution achieved by super-resolution microscopy techniques. Notably, the fast improvement of imaging instruments has not been reflected in the optimization of biological sample preparation. During recent years, large efforts have been made to generate affinity probes smaller than conventional antibodies adapted for fluorescent super-resolution imaging. In this review, we briefly discuss the current views on synaptic organization and necessary key technologies to progress in the understanding of synaptic physiology. We also highlight the challenges faced by current fluorescent super-resolution methods, and we describe the prerequisites for an ideal study of synaptic organization.

scholarly journals Intracellular β1-Adrenergic Receptors and Organic Cation Transporter 3 Mediate Phospholamban Phosphorylation to Enhance Cardiac Contractility

2020 ◽  
Author(s):  
Ying Wang ◽  
Qian Shi ◽  
Minhui Li ◽  
Meimi Zhao ◽  
Gopireddy Raghavender Reddy ◽  
...  
Keyword(s):  
Single Molecule ◽  
Organic Cation ◽  
Cardiac Contractility ◽  
Super Resolution ◽  
Organic Cation Transporter ◽  
Proximity Ligation ◽  
Resolution Imaging ◽  
Organic Cation Transporter 3 ◽  
And Function ◽  
Phospholamban Phosphorylation

Rationale: β 1 -adrenoceptors (β 1 ARs) exist at intracellular membranes and Organic Cation Transporter 3 (OCT3) mediates norepinephrine entry into cardiomyocytes. However, the functional role of intracellular β 1 AR in cardiac contractility remains to be elucidated. Objective: Test localization and function of intracellular β 1 AR on cardiac contractility. Methods and Results: Membrane fractionation, super-resolution imaging, proximity ligation, co-immunoprecipitation and single-molecule pulldown demonstrated a pool of β 1 ARs in mouse hearts that was associated with sarco/endoplasmic reticulum Ca 2+ -ATPase at the sarcoplasmic reticulum (SR). Local protein kinase A (PKA) activation was measured using a PKA biosensor targeted at either the plasma membrane (PM) or SR. Compared to wild type (WT), myocytes lacking OCT3 (OCT3KO) responded identically to the membrane-permeant βAR agonist isoproterenol in PKA activation at both PM and SR. The same was true at the PM for membrane-impermeant norepinephrine, but the SR response to norepinephrine was suppressed in OCT3KO myocytes. This differential effect was recapitulated in phosphorylation of the SR-pump regulator phospholamban. Similarly, OCT3KO selectively suppressed calcium transients and contraction responses to norepinephrine, but not isoproterenol. Furthermore, sotalol, a membrane-impermeant βAR-blocker suppressed isoproterenol-induced PKA activation at the PM, but permitted PKA activation at the SR, phospholamban phosphorylation and contractility. Moreover, pretreatment with sotatol in OCT3KO myocytes prevented norepinephrine induced PKA activation at both PM and the SR and contractility. Conclusions: Functional β 1 ARs exists at the SR and is critical for PKA-mediated phosphorylation of phospholamban and cardiac contractility upon catecholamine stimulation. Activation of these intracellular β 1 ARs requires catecholamine transport via OCT3.

scholarly journals Pathway-specific deregulation of striatal excitatory synapses in LRRK2 mutations

2020 ◽  
Author(s):  
Chuyu Chen ◽  
Giulia Soto ◽  
Nicholas Bannon ◽  
Shuo Kang ◽  
Yevgenia Kozorovitskiy ◽  
...  
Keyword(s):  
Ampa Receptors ◽  
Disease Onset ◽  
Super Resolution ◽  
Structure And Function ◽  
Projection Neurons ◽  
Indirect Pathway ◽  
Synaptic Structure ◽  
Resolution Imaging ◽  
Clinical Changes ◽  
And Function

ABSTRACTLRRK2 is a kinase expressed in striatal spiny projection neurons (SPNs), cells which lose dopaminergic input in Parkinson’s disease (PD). R1441C and G2019S are the most common pathogenic mutations of LRRK2. How these mutations alter the structure and function of individual synapses on direct and indirect pathway SPNs is unknown and may reveal pre-clinical changes in dopamine-recipient neurons that predispose towards disease. Here, R1441C and G2019S knock-in mice enabled thorough evaluation of dendritic spines and synapses on pathway-identified SPNs. Biochemical synaptic preparations and super-resolution imaging revealed increased levels and altered organization of glutamatergic AMPA receptors in LRRK2 mutants. Relatedly, decreased frequency of excitatory post-synaptic currents accompanied changes in dendritic spine nano-architecture, and single-synapse currents, evaluated using 2-photon glutamate uncaging. Overall, LRRK2 mutations reshaped synaptic structure and function, an effect exaggerated in R1441C dSPNs. These data open the possibility of new neuroprotective therapies aimed at SPN synapse function, prior to disease onset.

scholarly journals Pathway-specific dysregulation of striatal excitatory synapses by LRRK2 mutations

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Chuyu Chen ◽  
Giulia Soto ◽  
Vasin Dumrongprechachan ◽  
Nicholas Bannon ◽  
Shuo Kang ◽  
...  
Keyword(s):  
Ampa Receptors ◽  
Disease Onset ◽  
Super Resolution ◽  
Structure And Function ◽  
Projection Neurons ◽  
Indirect Pathway ◽  
Synaptic Structure ◽  
Resolution Imaging ◽  
Clinical Changes ◽  
And Function

LRRK2 is a kinase expressed in striatal spiny projection neurons (SPNs), cells which lose dopaminergic input in Parkinson’s disease (PD). R1441C and G2019S are the most common pathogenic mutations of LRRK2. How these mutations alter the structure and function of individual synapses on direct and indirect pathway SPNs is unknown and may reveal pre-clinical changes in dopamine-recipient neurons that predispose toward disease. Here, R1441C and G2019S knock-in mice enabled thorough evaluation of dendritic spines and synapses on pathway-identified SPNs. Biochemical synaptic preparations and super-resolution imaging revealed increased levels and altered organization of glutamatergic AMPA receptors in LRRK2 mutants. Relatedly, decreased frequency of miniature excitatory post-synaptic currents accompanied changes in dendritic spine nano-architecture, and single-synapse currents, evaluated using two-photon glutamate uncaging. Overall, LRRK2 mutations reshaped synaptic structure and function, an effect exaggerated in R1441C dSPNs. These data open the possibility of new neuroprotective therapies aimed at SPN synapse function, prior to disease onset.

scholarly journals Knockout of a single Sox gene resurrects an ancestral cell type in the sea anemone Nematostella vectensis

2021 ◽  
Author(s):  
Leslie S Babonis ◽  
Camille Enjolras ◽  
Abigail J Reft ◽  
Brent M Foster ◽  
Fredrik Hugosson ◽  
...  
Keyword(s):  
Cell Fate ◽  
Prey Capture ◽  
Mechanistic Explanation ◽  
Cell Types ◽  
Sea Anemone ◽  
Nematostella Vectensis ◽  
Sea Anemones ◽  
Form And Function ◽  
Sox Gene ◽  
And Function

Cnidocytes are the explosive stinging cells found only in cnidarians (corals, jellyfish, etc). Specialized for prey capture and defense, cnidocytes are morphologically complex and vary widely in form and function across taxa; how such diversity evolved is unknown. Using CRISPR/Cas9-mediated genome editing in the burrowing sea anemone Nematostella vectensis, we show that a single transcription factor (NvSox2) acts as a binary switch between two alternative cnidocyte fates. Knockout of NvSox2 caused a complete transformation of nematocytes (piercing cells) into spirocytes (ensnaring cells). The type of spirocyte induced by NvSox2 knockout (robust spirocyte) is not normally found in N. vectensis but is common in sea anemones from other habitats. Homeotic control of cell fate provides a mechanistic explanation for the discontinuous distribution of cnidocyte types across cnidarians and demonstrates how simple counts of cell types can underestimate biodiversity.

FEISEM, Form and Function in the Nuclear Pore Complex

1998 ◽  
Vol 4 (S2) ◽  
pp. 958-959
Author(s):  
T.D. Allen ◽  
G. R. Bcnnion ◽  
S. A. Rutherford ◽  
E. Kiscleva ◽  
M. W. Goldberg
Keyword(s):  
Nuclear Pore Complex ◽  
Considerable Increase ◽  
Structural Complexity ◽  
Nuclear Pore ◽  
Molecular Architecture ◽  
Structural Elements ◽  
Form And Function ◽  
Import And Export ◽  
And Function ◽  
High Degree

Recent initiatives have resulted in a considerable increase in our understanding of the structure of the nuclear pore complex (NPC). The biochemical factors involved in both import and export have been rapidly characterised, with steady progress in the molecular dissection of the structural elements of the NPC, which is a unit of considerable molecular architecture (MW 125 kD), comprising an estimated 50- 100 different proteins. Despite this progress, the crucial molecular interactions involved in the mechanics of transport through the central transporter of the NPC remain unclear. NPC structure in Diptera, fish, (Fig 1) amphibians, birds and mammals shows a high degree of evolutionary conservation. 3D reconstructions of isolated yeast NPCs, show that the core structure is very similar to ‘higher’ organisms, but peripheral structures may be considerably reduced in structural complexity (1).Individual NPC components have been accessed in FEISEM by a variety of methods, including proteolysis,

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