scholarly journals Targeted dynein inhibition generates flagellar beating

2017 ◽  
Author(s):  
Jianfeng Lin ◽  
Daniela Nicastro
Keyword(s):  
Molecular Mechanism ◽  
Structural Changes ◽  
Direct Evidence ◽  
Electron Tomography ◽  
Asymmetric Distribution ◽  
Conformational Switching ◽  
Cryo Electron Tomography ◽  
Cilia And Flagella ◽  
Biochemical Analyses ◽  
Sea Urchin Sperm

Motile cilia and flagella are highly conserved organelles that are essential for the normal development and health of many eukaryotes including humans. To reveal the molecular mechanism of motility, we used cryo-electron tomography of active sea urchin sperm flagella to directly visualize the macromolecular complexes and their structural changes during flagellar beating. We resolved distinct conformations of dynein motors and regulators, and showed that many of them are distributed in bend-direction-dependent fashion in active flagella. Our results provide direct evidence for the conformational switching predicted by the ‘switch-point-hypothesis’. However, they also reveal a fundamentally different mechanism of generating motility by inhibiting dyneins, rather than activating them, causing an asymmetric distribution of force and thus bending. Our high-resolution structural and biochemical analyses provide a new understanding of the distinct roles played by various dyneins and regulators in ciliary motility and suggest a molecular mechanism for robust beating in an all-or-none manner.

scholarly journals Tubulin glycylation controls axonemal dynein activity, flagellar beat, and male fertility

Science ◽  
2021 ◽  
Vol 371 (6525) ◽  
pp. eabd4914
Author(s):  
Sudarshan Gadadhar ◽  
Gonzalo Alvarez Viar ◽  
Jan Niklas Hansen ◽  
An Gong ◽  
Aleksandr Kostarev ◽  
...  
Keyword(s):  
Posttranslational Modifications ◽  
Male Fertility ◽  
Electron Tomography ◽  
Structural Basis ◽  
Cellular Functions ◽  
Flagellar Beat ◽  
Cryo Electron Tomography ◽  
Axonemal Dynein ◽  
Dynein Arms ◽  
Cilia And Flagella

Posttranslational modifications of the microtubule cytoskeleton have emerged as key regulators of cellular functions, and their perturbations have been linked to a growing number of human pathologies. Tubulin glycylation modifies microtubules specifically in cilia and flagella, but its functional and mechanistic roles remain unclear. In this study, we generated a mouse model entirely lacking tubulin glycylation. Male mice were subfertile owing to aberrant beat patterns of their sperm flagella, which impeded the straight swimming of sperm cells. Using cryo–electron tomography, we showed that lack of glycylation caused abnormal conformations of the dynein arms within sperm axonemes, providing the structural basis for the observed dysfunction. Our findings reveal the importance of microtubule glycylation for controlled flagellar beating, directional sperm swimming, and male fertility.

scholarly journals The CSC connects three major axonemal complexes involved in dynein regulation

2012 ◽  
Vol 23 (16) ◽  
pp. 3143-3155 ◽  
Author(s):  
Thomas Heuser ◽  
Erin E. Dymek ◽  
Jianfeng Lin ◽  
Elizabeth F. Smith ◽  
Daniela Nicastro
Keyword(s):  
Electron Tomography ◽  
Structural Heterogeneity ◽  
Flagellar Motility ◽  
Wild Type ◽  
Localization Model ◽  
Cryo Electron Tomography ◽  
Radial Spokes ◽  
Regulatory Complex ◽  
Health And Development ◽  
Cilia And Flagella

Motile cilia and flagella are highly conserved organelles that play important roles in human health and development. We recently discovered a calmodulin- and spoke-associ­ated complex (CSC) that is required for wild-type motility and for the stable assembly of a subset of radial spokes. Using cryo–electron tomography, we present the first structure-based localization model of the CSC. Chlamydomonas flagella have two full-length radial spokes, RS1 and RS2, and a shorter RS3 homologue, the RS3 stand-in (RS3S). Using newly developed techniques for analyzing samples with structural heterogeneity, we demonstrate that the CSC connects three major axonemal complexes involved in dynein regulation: RS2, the nexin–dynein regulatory complex (N-DRC), and RS3S. These results provide insights into how signals from the radial spokes may be transmitted to the N-DRC and ultimately to the dynein motors. Our results also indicate that although structurally very similar, RS1 and RS2 likely serve different functions in regulating flagellar motility.

scholarly journals Scaffold subunits support associated subunit assembly in the Chlamydomonas ciliary nexin-dynein regulatory complex

2019 ◽  
Author(s):  
Long Gui ◽  
Kangkang Song ◽  
Douglas Tristchler ◽  
Raqual Bower ◽  
Yan Si ◽  
...  
Keyword(s):  
Electron Tomography ◽  
Core Complex ◽  
Ciliary Motility ◽  
C Terminus ◽  
Large N ◽  
Cryo Electron Tomography ◽  
N Terminus ◽  
Regulatory Complex ◽  
Cilia And Flagella ◽  
Linker Domain

ABSTRACTThe nexin-dynein regulatory complex (N-DRC) in motile cilia and flagella functions as a linker between neighboring doublet microtubules, acts to stabilize the axonemal core structure, and serves as a central hub for the regulation of ciliary motility. Although the N-DRC has been studied extensively using genetic, biochemical, and structural approaches, the precise arrangement of the eleven (or more) N-DRC subunits remains unknown. Here, using cryo-electron tomography, we have compared the structure of Chlamydomonas wild-type flagella to that of strains with specific DRC subunit deletions or rescued strains with tagged DRC subunits. Our results show that DRC7 is a central linker subunit that helps connect the N-DRC to the outer dynein arms. DRC11 is required for the assembly of DRC8, and DRC8/11 form a sub-complex in the proximal lobe of the linker domain that is required to form stable contacts to the neighboring B-tubule. Gold labeling of tagged subunits determines the precise locations of the previously ambiguous N-terminus of DRC4 which is now shown to contribute to the core scaffold of the N-DRC and C-terminus of DRC5. Our results reveal the overall architecture of N-DRC, with the three subunits, DRC1/2/4 forming a core complex that serves as the scaffold for the assembly of the “functional subunits” associate, namely DRC3/5-8/11. These findings shed light on N-DRC assembly and its role in regulating flagellar beating.Significance StatementCilia and flagella are small hair-like appendages in eukaryotic cells that play essential roles in cell sensing, signaling, and motility. The highly conserved nexin-dynein regulatory complex (N-DRC) is one of the key regulators for ciliary motility. At least 11 proteins (DRC1–11) have been assigned to the N-DRC, but their precise arrangement within the large N-DRC structure is not yet known. Here, using cryo-electron tomography combined with genetic approaches, we have localized DRC7, the sub-complex DRC8/DRC11, the N-terminus of DRC4, and the C-terminus of DRC5. Our results provide insights into the N-DRC structure, its function in the regulation of dynein activity, and the mechanism by which n-drc mutations can lead to defects in ciliary motility that cause disease.

Proteomic analysis of microtubule inner proteins (MIPs) in Rib72 null Tetrahymena cells reveals functional MIPs

2020 ◽  
Author(s):  
Amy S. Fabritius ◽  
Brian A. Bayless ◽  
Sam Li ◽  
Daniel Stoddard ◽  
Westley Heydeck ◽  
...  
Keyword(s):  
Proteomic Analysis ◽  
Tetrahymena Thermophila ◽  
Electron Tomography ◽  
Functional Characterization ◽  
Ciliary Beating ◽  
Ciliary Function ◽  
Cryo Electron Tomography ◽  
Motile Cilia ◽  
Cilia And Flagella ◽  
Stable Populations

AbstractMotile cilia and flagella are built from stable populations of doublet microtubules that comprise their axonemes. Their unique stability is brought about, at least in part, by a network of Microtubule Inner Proteins (MIPs) found in the lumen of their doublet microtubules. Rib72A and Rib72B were identified as microtubule inner proteins (MIPs) in the motile cilia of Tetrahymena thermophila. Loss of these proteins leads to ciliary defects and loss of multiple MIPs. We performed mass spectrometry coupled with proteomic analysis and bioinformatics to identify the MIPs lost in RIB72A/B knockout (KO) Tetrahymena cells. From this analysis we identified a number of candidate MIPs and pursued one, Fap115, for functional characterization. We find that loss of Fap115 results in disrupted cell swimming and aberrant ciliary beating. Cryo-electron tomography reveals that Fap115 localizes to MIP6a in the A-tubule of the doublet microtubules. Overall, our results highlight the complex relationship between MIPs, ciliary structure, and ciliary function.

Cryo-Electron Tomography Reveals Novel Features of Cilia and Flagella

2012 ◽  
Vol 18 (S2) ◽  
pp. 554-555
Author(s):  
D. Nicastro ◽  
T. Heuser ◽  
J. Lin ◽  
C.F. Barber
Keyword(s):  
Electron Tomography ◽  
Cryo Electron Tomography ◽  
Cilia And Flagella

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

scholarly journals Microtubule plus-end regulation by centriolar cap proteins

2021 ◽  
Author(s):  
Funso E. Ogunmolu ◽  
Shoeib Moradi ◽  
Vladimir A. Volkov ◽  
Chris van Hoorn ◽  
Jingchao Wu ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Electron Tomography ◽  
In Vitro Reconstitution ◽  
Luminal Side ◽  
Cryo Electron Tomography ◽  
Direct Binding ◽  
Distal Centriole

Centrioles are microtubule-based organelles required for the formation of centrosomes and cilia. Centriolar microtubules, unlike their cytosolic counterparts, grow very slowly and are very stable. The complex of centriolar proteins CP110 and CEP97 forms a cap that stabilizes the distal centriole end and prevents its over-elongation. Here, we used in vitro reconstitution assays to show that whereas CEP97 does not interact with microtubules directly, CP110 specifically binds microtubule plus ends, potently blocks their growth and induces microtubule pausing. Cryo-electron tomography indicated that CP110 binds to the luminal side of microtubule plus ends and reduces protofilament peeling. Furthermore, CP110 directly interacts with another centriole biogenesis factor, CPAP/SAS-4, which tracks growing microtubule plus ends, slows down their growth and prevents catastrophes. CP110 and CPAP synergize in inhibiting plus-end growth, and this synergy depends on their direct binding. Together, our data reveal a molecular mechanism controlling centriolar microtubule plus-end dynamics and centriole biogenesis.

scholarly journals The flagellar motor of Vibrio alginolyticus undergoes major structural remodeling during rotational switching

2020 ◽  
Author(s):  
Brittany L. Carroll ◽  
Tatsuro Nishikino ◽  
Wangbiao Guo ◽  
Shiwei Zhu ◽  
Seiji Kojima ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Direct Evidence ◽  
Electron Tomography ◽  
Vibrio Alginolyticus ◽  
Flagellar Motor ◽  
Large Rearrangement ◽  
Structural Remodeling ◽  
Cryo Electron Tomography ◽  
Ring Structures ◽  
Bacterial Flagellar Motor

ABSTRACTThe bacterial flagellar motor is an intricate nanomachine that switches rotational directions between counterclockwise (CCW) and clockwise (CW) to direct the migration of the cell. The cytoplasmic ring (C-ring) of the motor, which is composed of FliG, FliM, and FliN, is known for controlling the rotational sense of the flagellum. However, the mechanism underlying rotational switching remains elusive. Here, we deployed cryo-electron tomography to visualize the C-ring in two rotational biased mutants (CCW-biased fliG-G214S and CW-locked fliG-G215A) in Vibrio alginolyticus. Sub-tomogram averaging was utilized to resolve two distinct conformations of the C-ring. Comparison of the C-ring structures in two rotational senses provide direct evidence that the C-ring undergoes major structural remodeling during rotational switch. Specifically, FliG conformational changes elicit a large rearrangement of the C-ring that coincides with rotational switching, whereas FliM and FliN form a spiral-shaped base of the C-ring, likely stabilizing the C-ring during the conformational remodeling.

scholarly journals Scaffold subunits support associated subunit assembly in the Chlamydomonas ciliary nexin–dynein regulatory complex

2019 ◽  
Vol 116 (46) ◽  
pp. 23152-23162 ◽  
Author(s):  
Long Gui ◽  
Kangkang Song ◽  
Douglas Tritschler ◽  
Raqual Bower ◽  
Si Yan ◽  
...  
Keyword(s):  
Electron Tomography ◽  
Wild Type ◽  
Core Complex ◽  
The Core ◽  
C Terminus ◽  
Cryo Electron Tomography ◽  
Regulatory Complex ◽  
Cilia And Flagella ◽  
Linker Domain ◽  
Shed Light

The nexin–dynein regulatory complex (N-DRC) in motile cilia and flagella functions as a linker between neighboring doublet microtubules, acts to stabilize the axonemal core structure, and serves as a central hub for the regulation of ciliary motility. Although the N-DRC has been studied extensively using genetic, biochemical, and structural approaches, the precise arrangement of the 11 (or more) N-DRC subunits remains unknown. Here, using cryo-electron tomography, we have compared the structure of Chlamydomonas wild-type flagella to that of strains with specific DRC subunit deletions or rescued strains with tagged DRC subunits. Our results show that DRC7 is a central linker subunit that helps connect the N-DRC to the outer dynein arms. DRC11 is required for the assembly of DRC8, and DRC8/11 form a subcomplex in the proximal lobe of the linker domain that is required to form stable contacts to the neighboring B-tubule. Gold labeling of tagged subunits determines the precise locations of the previously ambiguous N terminus of DRC4 and C terminus of DRC5. DRC4 is now shown to contribute to the core scaffold of the N-DRC. Our results reveal the overall architecture of N-DRC, with the 3 subunits DRC1/2/4 forming a core complex that serves as the scaffold for the assembly of the “functional subunits,” namely DRC3/5–8/11. These findings shed light on N-DRC assembly and its role in regulating flagellar beating.

scholarly journals Lemon-shaped halo archaeal virus His1 with uniform tail but variable capsid structure

2015 ◽  
Vol 112 (8) ◽  
pp. 2449-2454 ◽  
Author(s):  
Chuan Hong ◽  
Maija K. Pietilä ◽  
Caroline J. Fu ◽  
Michael F. Schmid ◽  
Dennis H. Bamford ◽  
...  
Keyword(s):  
Structural Changes ◽  
Electron Tomography ◽  
Host Cells ◽  
Biochemical Treatment ◽  
Archaeal Virus ◽  
Virus Life Cycle ◽  
Cryo Electron Tomography ◽  
Empty Tube ◽  
Subtomogram Averaging ◽  
Unusual Shape

Lemon-shaped viruses are common in nature but so far have been observed to infect only archaea. Due to their unusual shape, the structures of these viruses are challenging to study and therefore poorly characterized. Here, we have studied haloarchaeal virus His1 using cryo-electron tomography as well as biochemical dissociation. The virions have different sizes, but prove to be extremely stable under various biochemical treatments. Subtomogram averaging of the computationally extracted virions resolved a tail-like structure with a central tail hub density and six tail spikes. Inside the tail there are two cavities and a plug density that separates the tail hub from the interior genome. His1 most likely uses the tail spikes to anchor to host cells and the tail hub to eject the genome, analogous to classic tailed bacteriophages. Upon biochemical treatment that releases the genome, the lemon-shaped virion transforms into an empty tube. Such a dramatic transformation demonstrates that the capsid proteins are capable of undergoing substantial quaternary structural changes, which may occur at different stages of the virus life cycle.

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