Cell Motility PDF
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Editor-in-Chief: EliasGreenbaum,OakRidgeNationalLaboratory, OakRidge,Tennessee,USA JudithHerzfeld,DepartmentofChemistry, EditorialBoard: BrandeisUniversity,Waltham,Massachusetts,USA MasuoAizawa,DepartmentofBioengineering, MarkS.Humayun,DohenyEyeInstitute, TokyoInstituteofTechnology,Yokohama,Japan LosAngeles,California,USA OlafS.Andersen,DepartmentofPhysiology, PierreJoliot,InstitutedeBiologie Biophysics&MolecularMedicine, Physico-Chimique,FondationEdmond CornellUniversity,NewYork,USA deRothschild,Paris,France RobertH.Austin,DepartmentofPhysics, LajosKeszthelyi,InstituteofBiophysics,Hungarian PrincetonUniversity,Princeton,NewJersey,USA AcademyofSciences,Szeged,Hungary JamesBarber,DepartmentofBiochemistry, RobertS.Knox,DepartmentofPhysics ImperialCollegeofScience,Technology andAstronomy,UniversityofRochester,Rochester, andMedicine,London,England NewYork,USA HowardC.Berg,DepartmentofMolecular AaronLewis,DepartmentofAppliedPhysics, andCellularBiology,HarvardUniversity, HebrewUniversity,Jerusalem,Israel Cambridge,Massachusetts,USA StuartM.Lindsay,DepartmentofPhysics VictorBloomfield,DepartmentofBiochemistry, andAstronomy,ArizonaStateUniversity, UniversityofMinnesota,St.Paul,Minnesota,USA Tempe,Arizona,USA RobertCallender,DepartmentofBiochemistry, DavidMauzerall,RockefellerUniversity, AlbertEinsteinCollegeofMedicine, NewYork,NewYork,USA Bronx,NewYork,USA EugenieV.Mielczarek,DepartmentofPhysics BrittonChance,DepartmentofBiochemistry/ andAstronomy,GeorgeMasonUniversity,Fairfax, Biophysics,UniversityofPennsylvania, Virginia,USA Philadelphia,Pennsylvania,USA MarkolfNiemz,MedicalFacultyMannheim, StevenChu,DepartmentofPhysics, UniversityofHeidelberg,Mannheim,Germany StanfordUniversity,Stanford,California,USA V.AdrianParsegian,PhysicalScienceLaboratory, LouisJ.DeFelice,DepartmentofPharmacology, NationalInstitutesofHealth,Bethesda, VanderbiltUniversity,Nashville,Tennessee,USA Maryland,USA JohannDeisenhofer,HowardHughesMedical LindaS.Powers,NCDMF:ElectricalEngineering, Institute,TheUniversityofTexas,Dallas, UtahStateUniversity,Logan,Utah,USA Texas,USA EarlW.Prohofsky,DepartmentofPhysics, GeorgeFeher,DepartmentofPhysics, PurdueUniversity,WestLafayette,Indiana,USA UniversityofCalifornia,SanDiego,LaJolla, AndrewRubin,DepartmentofBiophysics,Moscow California,USA StateUniversity,Moscow,Russia HansFrauenfelder,CNLS,MSB258, MichaelSeibert,NationalRenewableEnergy LosAlamosNationalLaboratory,LosAlamos, Laboratory,Golden,Colorado,USA NewMexico,USA DavidThomas,DepartmentofBiochemistry, IvarGiaever,RensselaerPolytechnicInstitute, UniversityofMinnesotaMedicalSchool, Troy,NewYork,USA Minneapolis,Minnesota,USA SolM.Gruner,DepartmentofPhysics, Kaoru Yamanouchi, Department of Chemistry PrincetonUniversity,Princeton,NewJersey,USA Universityof Tokyo, Tokyo,Japan Peter Lenz (Ed.) Cell Motility PeterLenz FachbereichPhysik Philipps-UniversitätMarburg Renthof5 35032Marburg Germany ISBN:978-0-387-73049-3 e-ISBN:978-0-387-73050-9 LibraryofCongressControlNumber:2007938098 (cid:2)c 2008SpringerScience+BusinessMedia,LLC Allrightsreserved.Thisworkmaynotbetranslatedorcopiedinwholeorinpartwithoutthewritten permissionofthepublisher(SpringerScience+BusinessMedia,LLC,233SpringStreet,NewYork,NY 10013,USA),exceptforbriefexcerptsinconnectionwithreviewsorscholarlyanalysis.Useinconnection withanyformofinformationstorageandretrieval,electronicadaptation,computersoftware,orby similarordissimilarmethodologynowknownorhereafterdevelopedisforbidden. Theuseinthispublicationoftradenames,trademarks,servicemarksandsimilarterms,evenifthey arenotidentifiedassuch,isnottobetakenasanexpressionofopinionastowhetherornottheyare subjecttoproprietaryrights. Printedonacid-freepaper. 9 8 7 6 5 4 3 2 1 springer.com Preface Cell motility is a fascinating example of cell behavior that is fundamentally important to a number of biological and pathological processes. Motility of eukaryotic cells is based on a complex, self-organized, mechano-chemical ma- chineconsistingofcytoskeletal filaments andmolecular motors.This network is highly dynamic, but able to show precise spatial and temporal organiza- tion.Themachineisregulatedbyacomplexnetworkofbiochemicalreactions coupled to force and movement-generating processes. In general, the cytoskeleton is responsible for the movement of the entire cellandformovementswithinthecell.Thereare(roughly)twowaysbywhich cells can move: swimming (i.e., movement through liquid) and crawling (i.e., movement across a rigid surface). Swimming cells experience viscous forces that are orders of magnitude greater than inertial forces. Some cells move by undergoing a non-symmetric (i.e., non-reciprocal) sequence of shape changes. Othersusethewhippingofflagellaorthecoordinatedbeatingofciliatopropel themselves through the surrounding liquid. Themovementofcellsacrossrigidsurfacesisevenmorecomplex.Onehas to distinguish between crawling and gliding. Crawling of a cell (attached to a rigid substrate) requires the coordinated activity of the cytoskeleton, mem- brane,andadhesionsystem.Growingactinfilaments(typicallyorganizedinto cross-linked filament networks) exert forces on the membranes creating pro- jections(filopodia,lamellipodia,andpseudopodia)attheleadingedge.These attach then to the substrate, converting protrusion into movement along the substrate. Contraction of the cell then leads to forward motion that contin- ues as a tread-milling cycle of front protrusion and rear retraction. Gliding cells slide across a rigid substrate by various mechanisms. Examples include a twitching motion based on the retraction of pili or propulsion by slime ex- trusion. The bacterium Myxococcus xanthus has engines for both modes of motion, and switches between them depending on whether cells move indi- vidually or collectively. Gliding of eukaryotic cells is less common, but some parasites move this way by using an actomyosin-based machinery. VI Preface Many cellular processes involve transport and movements within the cell boundaries. For example, the replicated chromosomes have to be brought into one of the two daughter cells during mitosis. This process requires many coordinated movements and major structural changes in the cytoskeleton. Also, for many other large molecules and vesicles, the most direct way to specific locations within the cell is along cytoskeletal filaments. This direct transport (which is driven by molecular motors) is much more precise and quicker than diffusional motion. Molecularmotorsareessentialformanyprocessesofcellularmotion.There is a whole variety of different motor proteins. The most important classes include linear motors (such as myosin, kinesin, and dynein), rotatory motors (such as ATPsynthase and bacterial flagella), and nucleic acid motors (such as helicases and topoisomerases). The linear motors use ATP to move along filaments.Theyaremuchmorethansimpletransporters.Two-headedmotors attachtoadjacentfilamentsleadingtoslidingofoppositelyorientedfilaments whichisresponsiblefor,e.g.,musclecontraction.Incollectionsofmotorsthese inducedinteractionsgiverisetoacomplexcooperativebehaviorallowingcells to actively deform their shape. On the other hand, single motors can exhibit quite complex shape changes. For example, ATPsynthase (the motor that produces ATP) performs a rotational motion. Other rotatory motors enable bacteria to swim, such as the rotating flagellum of E.coli. The latter motors are brought to rotation by a proton or ion flux. Oneofthekeychallengesincellmotilityistodevelopacompletephysical understanding of how and why cells move. Considering the wealth of pro- cessestakingplaceinthesesystems,andthelargenumberofdifferentcellular componentsinvolved,itbecomesclearthatthiscanonlybealong-termgoal. Nevertheless, our understanding of cell motility has increased greatly during the last few years. Progress has been mainly driven by combined theoretical and experimental efforts in studying model systems, by the availability of de- tailed mechanical, biochemical, and structural data on key components, and by novel theoretical approaches in modeling motile cells. In this book, these new trends are illustrated by several reviews on specific examples of some of the fundamental phenomena and concepts of cell motility. Thefirstthreechaptersdealwiththebest-studiedmodelsystemsforactin- based cellular motion, namely Listeria, keratocytes and Dictyostelium. Many cellular movements are based on the dynamics of the actin network. Actin is often associated with myosin to produce the forces required for motion. However, this is not always necessary: the intracellular bacterium Listeria monocytogenes uses the host cell’s own actin machinery to propel itself. Its motionsimplyreliesonactinpolymerizationandcross-linkingofthenetwork. Inthissystem,theoreticalmodelinghasbeenverysuccessfulpartiallybecause actin-based propulsion can be investigated experimentally in reconstituted systems with purified proteins where beads replace the bacterium. The first chapterbyProstetal.summarizesthetheoreticalapproachesandthenewest experimental developments. Preface VII In whole-cell motility, the interplay between biochemical and mechanical processes is more complicated. Typically, a moving cell needs to coordinate theactionofalargenumberofindividualmolecularbuildingblocks.Whilethe molecular basis of these dynamical processes are beginning to be understood, only little is known about the large-scale mechanisms the cell uses to achieve coherentcellmovement.Asummaryofthecurrenteffortstobridgethisgapis givenbyKerenandTheriotinthesecondchapter.Theydescribetheanalysis of the interplay of biophysical aspects of actin-based cell motility with the underlying biochemical processes in fish epithelial keratocytes. Keratocytes appear to be the simplest available model system for this purpose because of their simple overall geometry and persistent motion. The role of the main mechanicalmodulesinvolvedinkeratocytemotility(namelytheactin-myosin cytoskeleton, the cell membrane, and the cytoplasmic fluid) is summarized, and their interplay with biochemical processes in the large-scale coordination of cell motility is discussed. The amoeba Dictyostelium discoideum, also a eukaryotic microorganism, moves by protrusion of pseudopods. In contrast to keratocytes and Listeria, however, this motion is directed. In response to starvation, the placement of pseudopods is controlled by the external concentration of a small molecule, cyclic AMP. Surface proteins sense this chemical information, which is then processed by a signal transduction network controlling actin dynamics. In the third chapter Levine and Rappel review theoretical efforts in modeling both the behavior of single cells and multicellular aggregation phenomena. Theyreportoncurrentsuccessesbutalsodemonstratethatrealisticmodelsof Dictyosteliummotilitywillultimatelyrequirethecombinationofamicroscopic description of the gradient-sensing system with the macroscopic mechanics of force generation, shape transformation, and cell translocation. Chapters 4 and 5 deal with the mechanical and structural properties of two very important components of the eukaryotic cytoskeleton. Dogterom et al. review the properties of microtubules in Chapter 4. These semi-flexible polymers form networks that fulfill various tasks in cells ranging from pro- viding tracks for motor proteins to dividing the duplicated chromosomes in replicatingcells.Thefocusofthiscontributionistheforce-generationbygrow- ing microtubules. Important experimental concepts as well as the theoretical framework required to explain the underlying conversion from chemical to mechanical energy are introduced. Molecular motors are the topic of the fifth chapter. Sarah Rice presents detailed structural data on kinesin, dynein, and myosin. It is shown how con- clusions can be drawn from this data about the conformational changes the motors undergo. The implications for our understanding of the mechanisms of motility and cargo-binding are analyzed. The sixth chapter is the only one concerned with motion based on the bacterial motility machinery. Makoto Miyata summarizes recent progress in our understanding of the gliding motility of Mycoplasma. These bacteria use membrane protrusions at a cell pole for motion. Their gliding machinery is VIII Preface composedofseveralproteinsthatcanundergorathercomplexshapechanges. The mysteries on how the bacterium is actually being pulled over the surface by this machinery are just being resolved. It becomes clear from Miyata’s review, however, that the involved proteins provide a cytoskeletal structure allowing bacterial motion. Recently,anewtheoreticaldescriptionofthecytoskeletonhasbeendevel- oped(independentlybyseveralgroups)thatisbasedongeneralizedhydrody- namic theories. Such approaches have been highly successful in describing a large variety of properties of complex fluids such as liquid crystals, polymers, and gels. Their extension to active systems (in which energy is continuously supplied by internal or external sources and internally consumed) is a very promising new approach to describe the dynamical properties of mixtures of cytoskeletal filaments and motor proteins. The contribution of Liverpool and Marchetti in Chapter 7 gives an overview on these current theoretical efforts. Collective effects in living matter are also the topic of the eighth chapter, inwhichphenomenaarisingfromhydrodynamicinteractionsinarraysofcilia and rotational motors are discussed. It is shown how these interactions can lead to coordination of ciliar beating and emergence of wave-like structures. Collective ciliar motion is not only important for feeding and swimming of cells, but also seems to play an essential role in the establishment of left and rightindevelopingvertebrates.Despiteconsiderableexperimentalprogressin investigating the generation of symmetry breaking fluid flow by ciliar beat- ing, some fundamental questions remain. Theoretical modeling might bevery helpful in clarifying some of these issues. The open questions are introduced together with the current theoretical efforts. Thisbookcontainsafewexamplesofbiologicalproblemsthatillustratethe wealth of novel phenomena one encounters in cell motility. The contributions demonstratethatatrulyinterdisciplinaryapproachisrequiredtosuccessfully investigate these systems. A key role is here played by physical concepts. Quantitative studies of moving cells and direct comparison between theory and experiment have only become possible by the application of ideas and models of hydrodynamics, elasticity theory, and statistical physics to living matter. In such a rapidly growing field, of course, many interesting developments anddiscoveriesarestilltocome.Thesereviews,however,alreadygiveusanin- dicationinwhichdirectionfutureresearchhastogo.Aswillbedemonstrated byseveralauthors,complexinterrelationshipsbetweendifferentmodularcom- ponentsarecharacteristicofbiologicalsystems.Newexperimentaltechniques have to be developed to extract information about the interactions between these components. On the theoretical side, models are needed that bridge the gap between molecular and macroscopic length scales coupling thus biochem- ical reactions with the mechanics of cellular motion. Finally, from the point of view of a theoretical physicist, it is highly excit- ing to observe that physical concepts and theoretical modeling are becoming increasingly important and accepted in biology, and in cell motility in par- Preface IX ticular. On the other hand, I think these developments are also of interest to physics itself because these living systems give us the opportunity to investi- gatesuchfundamentalphenomenaastransport,dynamicalphasetransitions, and emergence of order and pattern formation far from thermodynamic equi- librium in a completely novel context. Marburg, March 2007 Peter Lenz Contents List of Contributors ...........................................XIII 1 The Physics Of Listeria Propulsion Jacques Prost, Jean-Franc¸ois Joanny, Peter Lenz, C´ecile Sykes ........ 1 2 Biophysical Aspects of Actin-Based Cell Motility in Fish Epithelial Keratocytes Kinneret Keren, Julie A. Theriot .................................. 31 3 Directed Motility and Dictyostelium Aggregation Herbert Levine, Wouter-Jan Rappel ................................ 59 4 Microtubule Forces and Organization Marileen Dogterom, Julien Husson, Liedewij Laan, Laura Munteanu, Christian Tischer ................................................ 93 5 Mechanisms of Molecular Motor Action and Inaction Sarah Rice ......................................................117 6 Molecular Mechanism of Mycoplasma Gliding - A Novel Cell Motility System Makoto Miyata ..................................................137 7 Hydrodynamics and Rheology of Active Polar Filaments Tanniemola B. Liverpool, M. Cristina Marchetti .....................177 8 Collective Effects in Arrays of Cilia and Rotational Motors Peter Lenz ......................................................207 Index..........................................................237
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