Prezentace na téma: "Vnější páry mikrotubulů Středový pár Dyneinová raménka"— Transkript prezentace:
1 Vnější párymikrotubulůStředový párDyneinová raménkaRadiální paprskyPrůřez bičíkemBičíkyPrůřez bazálnímtělískemBazální tělískoPlazmatickámembránaTripletyPohyb bičíku
2 331 proteiny u Trypanosoma brucei, Bičík je tvořen cca331 proteiny u Trypanosoma brucei,279 proteiny u Chlamydomonas reinhardtii a263 proteiny u Tetrahymena thermophila.Jana a kol. 2013
3 Flagelární proteom trypanosomy a, Transmission electron micrograph showing the flagellum (arrow) and flagellar pocket (asterisk). b, The axoneme and the PFR. c, One-dimensional electrophoretic separation of isolated flagella. d, Distribution of TbFP protein homologues. e, Comparison of the T. brucei, Chlamydomonas reinhardtii (CrFPaxo) and T. thermophila flagellar proteomes. For each comparison, green indicates present in both; orange/red indicates present in opposing genome but not opposing proteome; blue/yellow indicates no homologue in opposing genome. Homology determined by alignment to each genome with reciprocal alignment by BLASTP. Scale bars, 1 m (a); 200 nm (b).
7 Na průřez se díváme směrem od báze, průměr mikrotubulů (A) je cca 25 nm.
8 Centrální mikrotubuly radial spokes and central apparatus may be involved in converting simple symmetric bends into the asymmetric waveforms required for forward swimming.Wakabayashi et al.  and Frey et al.  have demonstrated that isolated axonemes from central pairless and radial spokeless mutants reactivated at low ATP concentration also undergo modestwaveform conversion in response to changes in calcium concentration. Therefore, the central apparatus and radial spokes are not an absolute requirement for calcium-induced waveform conversion.Cilia and flagella with 9+2 axonemes generally have large amplitude, planar waveforms during at least one phase, if not the entire, beat cycle. It is possible that the CP/RS system contributes to the production of planar waveforms.Structural studies ofParamecia cilia revealed that the central apparatus rotates within the nine doubletmicrotubules; it rotates once per beat and with a slight twist that has the same period as that ofthe propagating bend [Omoto and Kung, 1979]. Rotation of the central pair has also beenobserved for flagella of other species including Chlamydomonas [reviewed in Omoto et al.,1999]. It is not known whether interactions of the central pair projections with the radial spokeheads during rotation induce tilt in the spokes relative to the circumferential axis of theaxoneme. If this is the case, then the radial spokes would potentially experience distortion intwo directions: longitudinally as the microtubules slide, and circumferentially as the centralapparatus rotates.From these combined studies, we can draw several conclusions independent of centralapparatus rotation. First, the orientation and asymmetry of the central apparatus most likelycorrelates with dynein activity on specific doublet microtubules. Second, the central pairprojections make contact with the radial spoke heads in cycles of detachment and reattachment.Based on the experimental results cited above, we propose that the CP/RS network of structuresoperates as both a mechanical and chemical transducer. Mechanical input includes interactionsbetween the radial spokes and central apparatus. Chemical input includes binding of secondmessengers, changes in enzymatic activity of anchored kinases and phosphatases, and localizedchanges in phosphorylation of axonemal proteins in the CP/RS control system. In each case,output involves changes in the physical and chemical properties of the radial spokes on subsetsof doublet microtubules for local control of dynein activity. Localized interactions of the radialspokes and central apparatus are predicted to differentially alter dynein activity on one side ofthe axoneme relative to the propagating bend [Mitchell, 2003a;Wargo and Smith, 2003]; thisaxonemal axis is defined by the inherent asymmetry of the central apparatus.Modulation of microtubule sliding by localized control of dynein activity may involve thelocalized phosphorylation of key regulatory proteins including subunits of the dynein arms[Hamasaki et al., 1991;Habermacher and Sale, 1997;King and Dutcher, 1997;Yang and Sale,2000;Christensen et al., 2001] and possibly components of the DRC. These modifications arenot likely to operate on the time scale of a single beat cycle to modulate the inherent oscillatorybehavior of beating cilia and flagella. Rather, additional beat parameters, such as waveformand stroke direction, most likely result from specific modifications that occur on a slower timecourse and affect particular axonemal components, including the dynein arms and CP/RSCell Motil Cytoskeleton. Author manuscript; available in PMC 2007 August 23.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscriptcontrol system. The continued molecular dissection of the CP/RS control system is essentialfor elucidating the physical and biochemical properties of the radial spokes and centralapparatus;Smith and Yang Page 8ChlamydomonasSpermie ježovkyVideo
9 Radiální paprsky - Chlamydomonas A transverse view of a Chlamydomonas flagellum as viewed looking proximal to distal; theouter doublet microtubules are numbered according to Hoops and Witman . Thedirection of the effective stroke is indicated by the arrow. Only doublet number one lacks anouter dynein arm. A single doublet microtubule (doublet one) with associated radial spoke, aswell as the entire central apparatus, is enlarged. The radial spoke diagram is further enlargedto include details of the possible location of particular radial spoke components. RSP2 servesas the primary stalk component and consists of GAF domains as well as calmodulin (CM)binding domains [Yang et al., 2002]. The central apparatus diagram is adapted from Mitchelland Sale . While PF6, PF16, PP1c, AKAP240, KRP, and KLP1 have been tentativelylocalized to specific central tubules (see Table I), it is unknown whether they localize to specificprojections. Therefore, they are listed above the central apparatus diagram. For references, seeTable I.
10 Na průřez se díváme směrem od báze, průměr mikrotubulů (A) je cca 25 nm.
13 Rychlost pohybu Většina bičíkovců – až 0,2 mm/s Dinoflageláti – až 0,5 mm/sNálevníci – až 1mm/sBičíky bijí normálně 50x, ale až 70x (Crithidia), 90x (úhoří spermie).
14 Rychlost částiceHustotaprostředíVelikost částiceReynoldsovo číslo je číslo které dává do souvislosti setrvačné síly a viskozitu (tedy odpor prostředí v důsledku vnitřního tření). Pomocí toho čísla je možné určit, zda je proudění tekutiny laminární a nebo turbulentní. Čím je Reynoldsovo číslo vyšší, tím nižší je vliv třecích sil částic tekutiny na celkový odpor.R=Viskozita prostředíν=μ/ρKinematická viskozita
15 Mezní vrstva (boundary layer) Rychlost částiceVelikost částiceReynoldsovo číslo je číslo které dává do souvislosti setrvačné síly a viskozitu (tedy odpor prostředí v důsledku vnitřního tření). Pomocí toho čísla je možné určit, zda je proudění tekutiny laminární a nebo turbulentní. Čím je Reynoldsovo číslo vyšší, tím nižší je vliv třecích sil částic tekutiny na celkový odpor.cccccR=νKinematická viskozita prostředí
35 Změny pohybu bičíků - Chlamydomonas Chemical signaling involves the interaction of second messengers, such as cyclic nucleotidemonophosphates and calcium [reviewed in Brokaw, 1987;Tash, 1989;Satir, 1995,1999] withconserved protein receptors and enzymes anchored to the axoneme, some of which arecomponents of the radial spokes and central apparatus (Table I). Motility changes mediated bythese second messengers include inducing quiescence in beating flagella, activating motility,increasing beat frequency, reversing the direction of the effective stroke, or changingwaveform. The effect of second messengers is mediated at least in part through secondmessenger-dependent kinases and phosphatases, such as cAMP-dependent protein kinase A(PKA), cGMP-dependent protein kinase (PKG), calmodulin dependent kinase, and calcineurin(PP2B) [Tash and Means, 1983;Tash et al., 1988;Chaudhry et al., 1995;San Agustin et al.,1998;Smith, 2002a]. It is possible that some second messengers affect motility by additionalmechanisms that are independent of phosphorylation. For example, several subunits of dyneinmotors are EF-hand proteins that may bind calcium directly, altering dynein activity [Pipernoet al., 1992;King and Patel-King, 1995;Yanagisawa and Kamiya, 2001;Casey et al.,2003;Guerra et al., 2003]. Chemical signaling also includes axonemal enzymes that are notdirectly sensitive to second messengers including casein kinase 1 (CK1), PP1, and PP2A, allof which appear to be involved in the control of dynein-driven motility [Walczak and Nelson,1993;Habermacher and Sale, 1996;Yang et al., 2000;Yang and Sale, 2000;Smith, 2002b].Diverse evidence indicates that the CP/RS system is not required for oscillatory beating of theaxoneme. Rather, the outer doublet microtubules and associated dynein arms appear to besufficient for the initiation and propagation of bends. Thus, the question remains, what is therole of the central apparatus and radial spokes? The simplest model is that the CP/RS systemperforms as a signal transducer for controlling the size and shape of the bend and for modifyingmotility in response to specific signals.
37 Membranely, CiryNejsou sice fyzicky spojeny, ale leží v mezní vrstvě souseda. V důsledku toho mají tendenci se pohybovat koordinovaně, aniž by musely být jinak regulovány.Computation of the Internal Forces in Cilia: Application to Ciliary Motion,the Effects of Viscosity, and Cilia InteractionsShay Gueron and Konstantin Levit-GurevichDepartment of Mathematics, Technion-Israel Institute of Technology, Haifa 32000, IsraelThis paper presents a simple and reasonable method for generating a phenomenological model of the internalmechanism of cilia. The model uses a relatively small number of parameters whose values can be obtained by fitting to ciliarybeat shapes. Here, we use beat patterns observed in Paramecium. The forces that generate these beats are computed andfit to a simple functional form called the “engine.” This engine is incorporated into a recently developed hydrodynamic modelthat accounts for interactions between neighboring cilia and between the cilia and the surface from which they emerge. Themodel results are compared to data on ciliary beat patterns of Paramecium obtained under conditions where the beats aretwo-dimensional. Many essential features of the motion, including several properties that are not built in explicitly, are shownto be captured. In particular, the model displays a realistic change in beat pattern and frequency in response to increasedviscosity and to the presence of neighboring cilia in configurations such as rows of cilia and two-dimensional arrays of cilia.We found that when two adjacent model cilia start beating at different phases they become synchronized within several beatperiods, as observed in experiments where two flagella are brought into close proximity. Furthermore, examination of variousmulticiliary configurations shows that an approximately antiplectic wave pattern evolves autonomously. This modelingevidence supports earlier conjectures that metachronism may occur, at least partially, as a self-organized phenomenon dueto hydrodynamic interactions between neighboring cilia.