scholarly journals THE STRUCTURAL BASIS OF CILIARY BEND FORMATION

1974 ◽  
Vol 63 (1) ◽  
pp. 35-63 ◽  
Author(s):  
Fred D. Warner ◽  
Peter Satir
Keyword(s):  
Relative Position ◽  
Main Part ◽  
Structural Basis ◽  
Radial Spoke ◽  
Local Displacement ◽  
Ciliary Motility ◽  
Local Contraction ◽  
Radial Spokes ◽  
Parallel Configuration

The sliding microtubule model of ciliary motility predicts that cumulative local displacement (Δl) of doublet microtubules relative to one another occurs only in bent regions of the axoneme. We have now tested this prediction by using the radial spokes which join the A subfiber of each doublet to the central sheath as markers of microtubule alignment to measure sliding displacements directly. Gill cilia from the mussel Elliptio complanatus have radial spokes lying in groups of three which repeat at 860 Å along the A subfiber. The spokes are aligned with the two rows of projections along each of the central microtubules that form the central sheath. The projections repeat at 143 Å and form a vernier with the radial spokes in the precise ratio of 6 projection repeats to 1 spoke group repeat. In straight regions of the axoneme, either proximal or distal to a bend, the relative position of spoke groups between any two doublets remains constant for the length of that region. However, in bent regions, the position of spoke groups changes systematically so that Δl (doublet 1 vs. 5) can be seen to accumulate at a maximum of 122 Å per successive 860-Å spoke repeat. Local contraction of microtubules is absent. In straight regions of the axoneme, the radial spokes lie in either of two basic configurations: (a) the parallel configuration where spokes 1–3 of each group are normal (90°) to subfiber A, and (b) the tilted spoke 3 configuration where spoke 3 forms an angle (θ) of 9–20°. Since considerable sliding of doublets relative to the central sheath (∼650 Å) has usually occurred in these regions, the spokes must be considered, functionally, as detached from the sheath projections. In bent regions of the axoneme, two additional spoke configurations occur where all three spokes of each group are tilted to a maximum of ± 33° from normal. Since the spoke angles do not lie on radii through the center of bend curvature, and Δl accumulates in the bend, the spokes must be considered as attached to the sheath when bending occurs. The observed radial spoke configurations strongly imply that there is a precise cycle of spoke detachment-reattachment to the central sheath which we conclude forms the main part of the mechanism converting active interdoublet sliding into local bending.

scholarly journals Structural insights into the cause of human RSPH4A primary ciliary dyskinesia

2021 ◽  
pp. mbc.E20-12-0806
Author(s):  
Yanhe Zhao ◽  
Justine Pinskey ◽  
Jianfeng Lin ◽  
Weining Yin ◽  
Patrick R. Sears ◽  
...  
Keyword(s):  
Primary Ciliary Dyskinesia ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Structural Basis ◽  
Radial Spoke ◽  
Radial Spokes ◽  
Cilia And Flagella ◽  
Tract Infections ◽  
Ciliary Dyskinesia

Cilia and flagella are evolutionarily conserved eukaryotic organelles involved in cell motility and signaling. In humans, mutations in Radial Spoke Head Protein 4 homolog A ( RSPH4A) can lead to primary ciliary dyskinesia (PCD), a life-shortening disease characterized by chronic respiratory tract infections, abnormal organ positioning, and infertility. Despite its importance for human health, the location of RSPH4A in human cilia has not been resolved, and the structural basis of RSPH4A-/- PCD remains elusive. Here, we present the native, three-dimensional structure of RSPH4A-/- human respiratory cilia using samples collected non-invasively from a PCD patient. Using cryo-electron tomography and subtomogram averaging, we compared the structures of control and RSPH4A-/- cilia, revealing primary defects in two of the three radial spokes (RSs) within the axonemal repeat and secondary (heterogeneous) defects in the central pair complex. Similar to RSPH1-/- cilia, the radial spoke heads of RS1 and RS2, but not RS3, were missing in RSPH4A-/- cilia. However, RSPH4A-/- cilia also exhibited defects within the arch domains adjacent to the RS1 and RS2 heads, which were not observed with RSPH1 loss. Our results provide insight into the underlying structural basis for RSPH4A-/- PCD and highlight the benefits of applying cryo-ET directly to patient samples for molecular structure determination. [Media: see text]

scholarly journals The CSC proteins FAP61 and FAP251 build the basal substructures of radial spoke 3 in cilia

2015 ◽  
Vol 26 (8) ◽  
pp. 1463-1475 ◽  
Author(s):  
Paulina Urbanska ◽  
Kangkang Song ◽  
Ewa Joachimiak ◽  
Lucja Krzemien-Ojak ◽  
Piotr Koprowski ◽  
...  
Keyword(s):  
Radial Spoke ◽  
Ciliary Motility ◽  
Distinct Structure ◽  
Radial Spokes ◽  
Dynein Arms ◽  
Motile Cilia ◽  
The Individual ◽  
And Function

Dynein motors and regulatory complexes repeat every 96 nm along the length of motile cilia. Each repeat contains three radial spokes, RS1, RS2, and RS3, which transduct signals between the central microtubules and dynein arms. Each radial spoke has a distinct structure, but little is known about the mechanisms of assembly and function of the individual radial spokes. In Chlamydomonas, calmodulin and spoke-associated complex (CSC) is composed of FAP61, FAP91, and FAP251 and has been linked to the base of RS2 and RS3. We show that in Tetrahymena, loss of either FAP61 or FAP251 reduces cell swimming and affects the ciliary waveform and that RS3 is either missing or incomplete, whereas RS1 and RS2 are unaffected. Specifically, FAP251-null cilia lack an arch-like density at the RS3 base, whereas FAP61-null cilia lack an adjacent portion of the RS3 stem region. This suggests that the CSC proteins are crucial for stable and functional assembly of RS3 and that RS3 and the CSC are important for ciliary motility.

scholarly journals FAP206 is a microtubule-docking adapter for ciliary radial spoke 2 and dynein c

2015 ◽  
Vol 26 (4) ◽  
pp. 696-710 ◽  
Author(s):  
Krishna Kumar Vasudevan ◽  
Kangkang Song ◽  
Lea M. Alford ◽  
Winfield S. Sale ◽  
Erin E. Dymek ◽  
...  
Keyword(s):  
Cell Motility ◽  
Electron Tomography ◽  
Macromolecular Complexes ◽  
Radial Spoke ◽  
Ciliary Motility ◽  
Cryo Electron Tomography ◽  
Ciliary Protein ◽  
Radial Spokes ◽  
Dynein Arms

Radial spokes are conserved macromolecular complexes that are essential for ciliary motility. A triplet of three radial spokes, RS1, RS2, and RS3, repeats every 96 nm along the doublet microtubules. Each spoke has a distinct base that docks to the doublet and is linked to different inner dynein arms. Little is known about the assembly and functions of individual radial spokes. A knockout of the conserved ciliary protein FAP206 in the ciliate Tetrahymena resulted in slow cell motility. Cryo–electron tomography showed that in the absence of FAP206, the 96-nm repeats lacked RS2 and dynein c. Occasionally, RS2 assembled but lacked both the front prong of its microtubule base and dynein c, whose tail is attached to the front prong. Overexpressed GFP-FAP206 decorated nonciliary microtubules in vivo. Thus FAP206 is likely part of the front prong and docks RS2 and dynein c to the microtubule.

scholarly journals A conserved CaM- and radial spoke–associated complex mediates regulation of flagellar dynein activity

2007 ◽  
Vol 179 (3) ◽  
pp. 515-526 ◽  
Author(s):  
Erin E. Dymek ◽  
Elizabeth F. Smith
Keyword(s):  
Mass Spectrometry ◽  
Sequence Similarity ◽  
Second Messengers ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Calcium Sensor ◽  
Wild Type ◽  
Radial Spoke ◽  
Radial Spokes ◽  
Dynein Arms

For virtually all cilia and eukaryotic flagella, the second messengers calcium and cyclic adenosine monophosphate are implicated in modulating dynein- driven microtubule sliding to regulate beating. Calmodulin (CaM) localizes to the axoneme and is a key calcium sensor involved in regulating motility. Using immunoprecipitation and mass spectrometry, we identify members of a CaM-containing complex that are involved in regulating dynein activity. This complex includes flagellar-associated protein 91 (FAP91), which shares considerable sequence similarity to AAT-1, a protein originally identified in testis as an A-kinase anchor protein (AKAP)– binding protein. FAP91 directly interacts with radial spoke protein 3 (an AKAP), which is located at the base of the spoke. In a microtubule sliding assay, the addition of antibodies generated against FAP91 to mutant axonemes with reduced dynein activity restores dynein activity to wild-type levels. These combined results indicate that the CaM- and spoke-associated complex mediates regulatory signals between the radial spokes and dynein arms.

scholarly journals Components of a "dynein regulatory complex" are located at the junction between the radial spokes and the dynein arms in Chlamydomonas flagella.

1994 ◽  
Vol 127 (5) ◽  
pp. 1311-1325 ◽  
Author(s):  
L C Gardner ◽  
E O'Toole ◽  
C A Perrone ◽  
T Giddings ◽  
M E Porter
Keyword(s):  
Liquid Chromatography ◽  
Cross Sections ◽  
Close Association ◽  
Longitudinal Section ◽  
Radial Spoke ◽  
Sds Page ◽  
Radial Spokes ◽  
Regulatory Complex ◽  
Dynein Arms ◽  
The Relationship

Previous studies of flagellar mutants have identified six axonemal polypeptides as components of a "dynein regulatory complex" (DRC). The DRC is though to coordinate the activity of the multiple flagellar dyneins, but its location within the axoneme has been unknown (Huang et al., 1982; Piperno et al., 1992). We have used improved chromatographic procedures (Kagami and Kamiya, 1992) and computer averaging of EM images (Mastronarde et al., 1992) to analyze the relationship between the DRC and the dynein arms. Our results suggest that some of the DRC components are located at the base of the second radial spoke in close association with the inner dynein arms. (a) Averages of axoneme cross-sections indicate that inner arm structures are significantly reduced in three DRC mutants (pf3 < pf2 < sup-pf-3 < wt). (b) These defects are more pronounced in distal/medial regions of the axoneme than in proximal regions. (c) Analysis of flagellar extracts by fast protein liquid chromatography and SDS-PAGE indicates that a specific dynein I2 isoform is missing in pf3 and reduced in pf2 and sup-pf-3. Comparison with ida4 and pf3ida4 extracts reveals that this isoform differs from those missing in ida4. (d) When viewed in longitudinal section, all three DRC mutants lack a crescent-shaped density above the second radial spoke, and pf3 axonemes lack additional structures adjacent to the crescent. We propose that the crescent corresponds in part to the location of the DRC, and that this structure is also directly associated with a subset of the inner dynein arms. This position is appropriate for a complex that is thought to mediate signals between the radial spokes and the dynein arms.

scholarly journals Radial spokes of Chlamydomonas flagella: genetic analysis of assembly and function.

1981 ◽  
Vol 88 (1) ◽  
pp. 80-88 ◽  
Author(s):  
B Huang ◽  
G Piperno ◽  
Z Ramanis ◽  
D J Luck
Keyword(s):  
Gene Product ◽  
Biochemical Analysis ◽  
Indirect Evidence ◽  
Mutant Gene ◽  
Molecular Defect ◽  
Molecular Weight Range ◽  
Radial Spoke ◽  
Radial Spokes ◽  
And Function

In addition to the previously studied pf-14 and pf-1 loci in Chlamydomonas reinhardtii, mutations for another five genes (pf-17, pf-24, pf-25, pf-26, and pf-27) have been identified and characterized as specifically affecting the assembly and function of the flagellar radial spokes. Mutants for each of the newly identified loci show selective alterations for one or more of the 17 polypeptides in the molecular weight range of 20,000-130,000 which form the radial spoke structure. In specific instances the molecular defect has been correlated with altered radial spoke morphology. Biochemical analysis of in vivo complementation in mutant X wild-type dikaryons has provided indirect evidence that mutations for four of the five new loci (pf-17, pf-24, pf-25, and pf-26) reside in structural genes for spoke components. In the case of pf-24, the identity of the mutant gene product was supported by analysis of induced intragenic revertants. In contrast to the other radial spoke mutants thus far investigated, evidence suggests that the gene product in pf-27 is extrinsic to the radial spokes and is required for the specific in vivo phosphorylation of spoke polypeptides.

scholarly journals Distinct architecture and composition of mouse axonemal radial spoke head revealed by cryo-EM

2019 ◽  
Author(s):  
Wei Zheng ◽  
Fan Li ◽  
Zhanyu Ding ◽  
Hao Liu ◽  
Lei Zhu ◽  
...  
Keyword(s):  
Interaction Network ◽  
Core Complex ◽  
Central Pair ◽  
Radial Spoke ◽  
Ciliary Motility ◽  
Axonemal Dynein ◽  
Compact Body ◽  
Dynein Arms

AbstractThe radial spoke (RS) transmits mechanochemical signals from the central pair apparatus (CP) to axonemal dynein arms to coordinate ciliary motility. The RS head, directly contacting with CP, differs dramatically in morphology between protozoan and mammal. Here we show the murine RS head is compositionally distinct from the Chlamydomonas one. Our reconstituted murine RS head core complex consists of Rsph1, Rsph3b, Rsph4a, and Rsph9, lacking Rsph6a whose orthologue exists in the Chlamydomonas RS head. We present the unprecedented cryo-EM structure of RS head core complex at 4.5-Å resolution and identified the subunit location and their interaction network. In this complex, Rsph3b, Rsph4a, and Rsph9 forms a compact body with Rsph4a serving possibly as an assembly scaffold and Rsph3b in a location that might link the head with stalk. Interestingly, two Rsph1 subunits constitute the two stretching-arms possibly for optimized RS-CP interaction. We also propose a sawtooth model for the RS-CP interaction. Our study suggests that the RS head experiences profound remodeling to probably comply with both structural and functional alterations of the axoneme during evolution.

scholarly journals Localization of Calmodulin and Dynein Light Chain Lc8 in Flagellar Radial Spokes

2001 ◽  
Vol 153 (6) ◽  
pp. 1315-1326 ◽  
Author(s):  
Pinfen Yang ◽  
Dennis R. Diener ◽  
Joel L. Rosenbaum ◽  
Winfield S. Sale
Keyword(s):  
Light Chain ◽  
Crucial Role ◽  
Cross Linking ◽  
Dynein Light Chain ◽  
Flagellar Motility ◽  
Radial Spoke ◽  
Size And Shape ◽  
Radial Spokes ◽  
Chemical Cross Linking

Genetic and in vitro analyses have revealed that radial spokes play a crucial role in regulation of ciliary and flagellar motility, including control of waveform. However, the mechanisms of regulation are not understood. Here, we developed a novel procedure to isolate intact radial spokes as a step toward understanding the mechanism by which these complexes regulate dynein activity. The isolated radial spokes sediment as 20S complexes that are the size and shape of radial spokes. Extracted radial spokes rescue radial spoke structure when reconstituted with isolated axonemes derived from the radial spoke mutant pf14. Isolated radial spokes are composed of the 17 previously defined spoke proteins as well as at least five additional proteins including calmodulin and the ubiquitous dynein light chain LC8. Analyses of flagellar mutants and chemical cross-linking studies demonstrated calmodulin and LC8 form a complex located in the radial spoke stalk. We postulate that calmodulin, located in the radial spoke stalk, plays a role in calcium control of flagellar bending.

scholarly journals Three-dimensional structure of the radial spokes reveals heterogeneity and interactions with dyneins in Chlamydomonas flagella

2012 ◽  
Vol 23 (1) ◽  
pp. 111-120 ◽  
Author(s):  
Cynthia F. Barber ◽  
Thomas Heuser ◽  
Blanca I. Carbajal-González ◽  
Vladimir V. Botchkarev ◽  
Daniela Nicastro
Keyword(s):  
Electron Tomography ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Flagellar Motility ◽  
Three Dimensional Structure ◽  
Radial Spoke ◽  
Cryo Electron Tomography ◽  
Radial Spokes ◽  
Axonemal Dynein ◽  
Subtomogram Averaging

Radial spokes (RSs) play an essential role in the regulation of axonemal dynein activity and thus of ciliary and flagellar motility. However, few details are known about the complexes involved. Using cryo–electron tomography and subtomogram averaging, we visualized the three-dimensional structure of the radial spokes in Chlamydomonas flagella in unprecedented detail. Unlike many other species, Chlamydomonas has only two spokes per axonemal repeat, RS1 and RS2. Our data revealed previously uncharacterized features, including two-pronged spoke bases that facilitate docking to the doublet microtubules, and that inner dyneins connect directly to the spokes. Structures of wild type and the headless spoke mutant pf17 were compared to define the morphology and boundaries of the head, including a direct RS1-to-RS2 interaction. Although the overall structures of the spokes are very similar, we also observed some differences, corroborating recent findings about heterogeneity in the docking of RS1 and RS2. In place of a third radial spoke we found an uncharacterized, shorter electron density named “radial spoke 3 stand-in,” which structurally bears no resemblance to RS1 and RS2 and is unaltered in the pf17 mutant. These findings demonstrate that radial spokes are heterogeneous in structure and may play functionally distinct roles in axoneme regulation.

scholarly journals Mutations in Hydin impair ciliary motility in mice

2008 ◽  
Vol 180 (3) ◽  
pp. 633-643 ◽  
Author(s):  
Karl-Ferdinand Lechtreck ◽  
Philippe Delmotte ◽  
Michael L. Robinson ◽  
Michael J. Sanderson ◽  
George B. Witman
Keyword(s):  
Fluid Transport ◽  
Beat Frequency ◽  
Ciliary Beat Frequency ◽  
Flagellar Motility ◽  
Wild Type ◽  
Central Pair ◽  
Ciliary Motility ◽  
Pair Defect ◽  
Radial Spokes ◽  
The Brain

Chlamydomonas reinhardtii hydin is a central pair protein required for flagellar motility, and mice with Hydin defects develop lethal hydrocephalus. To determine if defects in Hydin cause hydrocephalus through a mechanism involving cilia, we compared the morphology, ultrastructure, and activity of cilia in wild-type and hydin mutant mice strains. The length and density of cilia in the brains of mutant animals is normal. The ciliary axoneme is normal with respect to the 9 + 2 microtubules, dynein arms, and radial spokes but one of the two central microtubules lacks a specific projection. The hydin mutant cilia are unable to bend normally, ciliary beat frequency is reduced, and the cilia tend to stall. As a result, these cilia are incapable of generating fluid flow. Similar defects are observed for cilia in trachea. We conclude that hydrocephalus in hydin mutants is caused by a central pair defect impairing ciliary motility and fluid transport in the brain.

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