This book, like other monographs of the Cellular Organelles series, is not a comprehensive review, but an introduction to the study of cytoskeleton. Accordingly, we describe only the main facts and concepts related to cyto- skeleton. Needless to say, selection and interpretation was influenced by the personal interests and opinions of the authors, although we attempted to be as fair as possible. We wished to familiarize the reader not only with well- established facts, but with current unsolved problems. Therefore, the words "possibly," "maybe," "not known," and "not clear" are much more frequent in this text than in many others. In accordance with the style of the series, relatively short lists of addi- tional readings are given at the end of each chapter; these lists contain mostly the recent reviews and a few original papers describing certain phenomena in detail. Few references are cited in the text; these citations are given to help the reader find the source of certain new data and theories, which are not discussed at length in the reviews. In contrast, many well-established facts and widely known theories are not cited.
1. Components of Cytoskeleton.- 1 Systems of Actin Filaments.- I. Introduction: The Main Types of Actin Structures.- A. Components of Actin Structures.- B. The Main Types of Structures Formed by Actin Filaments.- C. Association of Actin Structures with Plasma Membrane.- D. Basic Processes Essential for Formation and Function of Actin Structures.- II. Structure of Globular and Filamentous Actins.- A. Amino Acid Sequences of Actins.- B. Form of Actin Molecules.- C. Structure of Actin Filament.- III. Polymerization of Actin.- A. Conditions and Manifestations of Polymerization.- B. Two Stages of Actin Polymerization: Nucleation and Elongation.- C. Elongation: The Role of ATP.- D. Elongation: Differences of Two Filament Ends.- IV. Agents Regulating Actin Polymerization.- A. Proteins Sequestering Actin Monomers.- B. Proteins Binding the Ends of Filaments (Capping Proteins).- C. Proteins Binding along the Filament (Side-Binding Proteins).- D. Cytochalasins.- E. Phalloidin.- V. Proteins Cross-Linking Actin Filaments.- A. Cross-Linking of Filaments in Vitro.- B. The Main Groups of Cross-Linking Proteins.- C. Function of Cross-Linking Proteins in the Cell.- VI. Proteins Attaching Actin Filament to the Membrane.- VII. Myosins.- A. Nonpolymerized Myosin.- B. Polymorphism of Myosins.- C. Polymerization.- D. Phosphorylation of Myosin and Regulation of Polymerization.- E. Formation of Myosin Filaments in the Cell.- VIII. Organization of Actin-Myosin Motile Systems.- A. Molecular Interactions of Myosin with Actin and ATP.- B. Motility of Various Model Systems Containing Actin and Myosin.- IX. Regulation of Contractility in Actin-Myosin Systems.- A. Regulation of the State of Myosin.- B. Modulation of the State of Actin-Attached Tropomyosin-Troponin Complex.- C. Solation and Gelation of Actin Gels.- D. Calcium Regulation of Contraction in Different Cells.- X. Conclusion: Dynamics of Actin Systems.- Literature Cited.- Additional Readings.- 2 Systems of Microtubules.- I. Introduction: Microtubular Structures in the Cell.- A. Components of Microtubular Structures.- B. Morphology of Microtubular Structures.- C. Basic Processes Essential for the Formation and Function of Microtubular Systems.- II. Tubulin.- A. Amino Acid Sequences.- B. Properties of Tubulin Dimers.- III. Structure of the Microtubule.- A. Protofilament.- B. Variants of Microtubules.- C. Polarity of Microtubules.- IV. Polymerization and Depolymerization of Tubulin.- A. Conditions of Polymerization.- B. Nucleation of Microtubules.- C. Elongation.- V. Microtubule-Associated Proteins.- A. The Main Types of MAPS.- B. Effects of MAPs on Polymerization and Depolymerization of Tubulin in Vitro.- C. Regulation of the State of MAPs.- D. Functions of MAPs in the Cell.- VI. Effects of Specific Drugs on Polymerization of Tubulin.- VII. Function and Formation of Microtubule-Organizing Centers.- A. The Main Types of MTOCs.- B. Nucleation and Stabilization of Microtubules by MTOCs in Vitro.- C. Determination of the Structure of Microtubular Arrays by MTOCs.- D. Formation of MTOCs.- VIII. Motility of Microtubular Systems.- A. Dyneins.- B. Dynein Interactions with Microtubules.- C. Organization and Regulation of the Movements of Cilia and Flagella.- IX. Conclusion: Dynamics of Microtubular Systems.- Literature Cited.- Additional Readings.- 3 Systems of Intermediate Filaments.- I. General Morphology of Structures Formed by Intermediate Filaments.- II. Proteins of Intermediate Filaments.- A. Isolation.- B. Five Classes of IF-Proteins.- C. Common and Specific Features of Different IF-Proteins.- III. Formation and Structure of Intermediate Filaments.- A. Polymerization of Filaments.- B. The Structure of 10-nm Filaments.- C. Intermediate Filament-Associated Proteins (IFAPs).- IV. Dynamics of Intermediate Filaments in the Cells.- A. Rearrangements of Filaments.- B. Alterations of Protein Composition of Filaments.- Literature Cited.- Additional Readings.- 4 Unconventional Fibrillar Structures in the Cytoplasm.- I. Thin Nonactin Filaments.- A. The Spasmoneme of the Vorticellid Ciliates.- B. Striated Rootlets of Cilia and Flagella.- C. Nematode Sperm Movements.- D. 2-nm Filaments in Muscle Sarcomere.- E. Connecting Filaments.- F. Conclusion.- II. The Problem of Microtrabecular Lattice.- Literature Cited.- Additional Readings.- II. General Organization and Function of Cytoskeleton.- 5 Cytoskeleton and Internal Organization of the Cell.- I. Introduction.- II. Integrated Structure of Cytoskeleton.- A. General Organization of Cytoskeleton in Various Types of Cells.- B. Interdependence of Various Cytoskeletal Systems.- C. The Links between Various Types of Fibrils.- III. Cytoskeleton and Distribution of Cellular Organelles.- IV. Cytoskeleton and Intracellular Movement of Organelles.- A. Various Forms of Intracellular Motility.- B. Rotational Movements of Organelles and Cytoplasm.- C. Radial Movements of Organelles.- V. Cytoskeleton Control of Distribution and Movement of Components of Plasma Membrane.- A. Immobilization of Membrane Components by Cortical Cytoskeleton.- B. Effects of External Ligands on the Membrane- Cytoskeleton Anchorage.- C. Directional Movements of Membrane Components.- D. Endocytosis.- E. Cytoskeletal Arrays as Sensors of Mechanical Stimuli.- VI. Cytoskeleton and Nucleus.- VII. Conclusion: Self-Integration of Cytoskeleton and of the Cellular Organization.- Literature Cited.- Additional Readings.- 6 Regulation of Synthesis of Cytoskeletal Proteins.- I. Introduction.- II. Flagellar Regeneration in Chlamydomonas: Induction of Synthesis of Cytoskeletal Protein.- III. Differentiation of NaegJeria: Alternative Expression of Actin and Tubulin Genes.- IV. Differential Expressions of Genes in Multigene Families Coding Tubulins, Actins, and Myosins.- V. Regulation of the Synthesis of Intermediate Filament Proteins in Cell Cultures: The Role of Cell Shape and Cell-Cell Interactions.- VI. Unpolymerized Tubulin Modulates the Level of Tubulin Synthesis: Specific Feedback Control of the Synthesis.- VII. Incorporation of Synthesized Proteins into Cytoskeletal Structures.- VIII. Conclusion.- Literature Cited.- Additional Readings.- 7 Reorganization of Cytoskeleton: Morphogenesis and Locomotion of Pseudopod-Forming Cells.- I. Introduction: The Main Features of Pseudopodial Reactions.- II. Morphological Reorganization Based on Pseudopodial Reactions.- A. Spreading and Locomotion of Fibroblasts.- B. Spreading of Epitheliocytes and Formation of Epithelial Sheets.- C. Neurons: The Growth of Neurites.- D. Movement of Polynuclear Leukocytes and of Amebae.- E. Spreading of Platelets.- F. Alterations of Cytoskeleton during Various Morphological Reorganizations.- III. Reorganization of Actin Cytoskeleton during Pseudopodial Reactions.- A. Mechanisms of the Extensions of Pseudopods.- B. Retraction of Pseudopods.- C. Attachment of Pseudopods.- D. Reorganization of Actin Structures Anchored to the Contacts.- IV. Factors Controlling the Distribution of Pseudopods: Reorganization of Microtubules.- V. Common and Special Features of Cytoskeletal Reorganization in Various Classes of Pseudopod-Forming Cells.- VI. Integration of Morphogenetic Reactions of Many Cells.- VII. Conclusion.- Literature Cited.- Additional Readings.- 8 Reorganization of Cytoskeleton: Cell Division.- I. Introduction.- II. Formation of the Spindle.- III. Reorganization of the Spindle Leading to Chromatid Separation.- A. Dynamic Equilibrium of the Metaphase Spindle.- B. Poleward Movement of Kinetochores.- C. Elongation of the Spindle.- IV. Cytokinesis.- V. Induction and Coordination of Mitotic Events.- Literature Cited.- Additional Readings.- 9 Neoplastic Transformations: Possible Unexplored Functions of Cytoskeleton.- I. Introduction.- II. Deficient Morphogenetic Reactions of Transformed Fibroblasts.- A. General Characteristics of Transformations.- B. Morphological Alterations of Transformed Cells.- C. Mechanisms of Abnormal Regulation of the Cytoskeletal Organization in Transformed Cells.- III. Possible Role of Cytoskeleton in the Regulation of Proliferation.- A. Abnormal Regulation of Proliferation in Transformed Cells.- B. Is Reorganization of Cytoskeleton Essential for Growth Activation by Oncoproteins?.- C. Dependence of Proliferation of Normal Cells on Their Shape.- IV. Conclusion: Possible Role of Cytoskeleton in the Reprogramming of Cellular Syntheses.- Literature Cited.- Additional Readings.