The Actin Cytoskeleton

Actin is one of the most abundant proteins and ubiquitously expressed in all eukaryotes. In recent years, the analysis of structure and function of such complexes has shed new light on actin's role in cellular and tissue morphogenesis, locomotion and various forms of intracellular motility, but also on its role in nuclear processes like chromatin architecture and transcription. Progress in understanding these different physiological phenomena, but also in unravelling the basis of actin-based pathophysiological processes has been made by combining video microscopy, molecular biology, genetics and biochemistry. Thus, the current research on actin, as ongoing in many international laboratories, is a "hot spot" in basic and translational research in life sciences. In this book on "The Actin Cytoskeleton", twelve internationally renowned authors present specific chapters that cover their recent work concerned with the various roles of actin mentioned above. This comprehensive volume is therefore an attractive handbook for teachers and students in many fields of medicine and pharmacology.

This Special Issue of IJMS covers a broad range of cutting-edge aspects related to the organization, function, and role in disease of the actin cytoskeleton. This cellular structure is of fundamental importance for the homeostasis of every eukaryotic cell, from the simplest unicellular organism to the most complex animal cell. The actin cytoskeleton contributes to developing and maintaining cell shape and tissue integrity and is crucial for cell migration, movement of organelles, vesicle trafficking, and the completion of cell division. Elaborate structures like the sarcomere, the inner ear cell stereocilia, and the brush border microvilli are built on actin filament scaffolds. Dozens of actin-binding proteins orchestrate the dynamic remodeling of the actin cytoskeleton and integrate it with microtubules and intermediate filaments and with the cell signaling machinery. Playing such fundamental roles in a plethora of cellular processes, it comes as no surprise that defects in actin and associated proteins have been found to be implicated in pathological conditions as diverse as myopathies and neurodegenerative diseases. This Special Issue gathers 15 contributions highlighting the impressive advances made in recent years in this exciting field.

The cell is no longer considered to be a bag full of enzymes dissolved in a liquid cytoplasm. It is now known that the cytoplasm is an exquisitely ordered structure of properly placed organelles and enzyme complexes that are suspended from an intricate network of structural protein polymers termed the cytoskeleton. All movement of organelles and vesicles within the cell is regulated by this cytoskeleton, and it is clear that the cytoskeleton is responsible for all of the cell's external movement as well. In this lecture, we will consider how the cytoskeleton elicits cell migration.The three main elements of the cytoskeleton are microtubules, intermediate filaments, and actin filaments. Microtubules are essential for (a) intracellular transport within the cytoplasm and transport between the nucleus and cytoplasm, (b) the structure and movement of all cilia and flagella, and (c) the structure of the mitotic spindle and movement of chromosomes on the spindle during cell division. Intermediate filaments give structural integrity to virtually all cells and tissues by providing an intracellular network of flexible cables that strengthen internal cell structure and stabilize cell-to-cell adhesion. It is this intercellular binding property that stably joins epithelial cells together to provide the protective functions of skin and the integrity of the intestinal mucosa.Actin is a highly conserved protein ubiquitous to all eukaryotic cells. Actin is absolutely required for (a) cell migration, (b) the contraction of muscle (both striated and smooth), (c) the structure and function of many cell protrusions (e.g., microvilli, filopodia, lamellopodia, blood platelet projections), (d) division of the cytoplasm (cytokinesis) during telophase of cell mitosis, and (e) movement and placement of organelles within the cell. Actin filaments are also called thin filaments because of their very slender (70 Ã…) diameter.

The mammalian cytoskeleton is an internal framework of actin, tubulin, and intermediate filament proteins. Proteins of these three classes assemble non-covalently into filamentous polymers that support the structural integrity of the relatively fragile lipid plasma membrane. In addition, cytoskeletal polymers provide the mechanical strength that hold a cell together and anchor it to its growth substrate. The cytoskeleton must also have the capacity for rapid and substantial remodeling and provide the motive and tractor force necessary to drive motility. As such, the cytoskeleton has a functional duality: sufficiently rigid to prevent plasma membrane deformation but pliable enough to allow for cytokinesis; sufficiently adhesive to allow for traction but dynamic enough to allow movement from one place to another. A major research challenge in cytoskeleton biology is to understand how cytoskeletal proteins assemble and dissemble in support of physiological processes. This chapter will focus on the role of the actin cytoskeleton in cell migration. More specifically, we will focus on the actin cytoskeleton of vertebrate cells. Table of Contents: Introduction / The Fundamentals of Actin Polymerization / Accessory Proteins Regulate Actin Polymerization and Assembly / Cellular Actin Structure / Cell Migration / Summary of Cell Migration / References / Author Biography

The cytoskeleton is the intracellular filament system that controls the morphology of a cell, allows it to move, and provides trafficking routes for intracellular transport. It comprises three major filament systems-actin, microtubules, and intermediate filaments-along with a host of adaptors, regulators, molecular motors, and additional structural proteins. This textbook presents a comprehensive and up-to-date view of the cytoskeleton, cataloguing its many different components and explaining how they are functionally integrated in different cellular processes. It starts by laying out the basic molecular hardware, before describing in detail how these components are assembled in cells and linked to neighboring cells and the extracellular matrix to maintain tissue architecture. It then surveys the roles of the cytoskeleton in processes such as intracellular transport, cell motility, signal transduction, and cell division. The book is thus essential reading for students learning about intracellular structure. It also represents a vital reference for all cell and developmental biologists working in this field.

A Top 25 CHOICE 2016 Title, and recipient of the CHOICE Outstanding Academic Title (OAT) Award. How much energy is released in ATP hydrolysis? How many mRNAs are in a cell? How genetically similar are two random people? What is faster, transcription or translation?Cell Biology by the Numbers explores these questions and dozens of others provid

Actin is an extremely abundant protein that comprises a dynamic polymeric network present in all eukaryotic cells, known as the actin cytoskeleton. The structure and function of the actin cytoskeleton, which is modulated by a plethora of actin-binding proteins, performs a diverse range of cellular roles. Well-documented functions for actin include: providing the molecular tracks for cytoplasmic streaming and organelle movements; formation of tethers that guide the cell plate to the division site during cytokinesis; creation of honeycomb-like arrays that enmesh and immobilize plastids in unique subcellular patterns; supporting the vesicle traffic and cytoplasmic organization essential for the directional secretory mechanism that underpins tip growth of certain cells; and coordinating the elaborate cytoplasmic responses to extra- and intracellular signals. The previous two decades have witnessed an immense accumulation of data relating to the cellular, biochemical, and molecular aspects of all these fundamental cellular processes. This prompted the editors to put together a diverse collection of topics, contributed by established international experts, related to the plant actin cytoskeleton. Because the actin cytoskeleton impinges on a multitude of processes critical for plant growth and development, as well as for responses to the environment, the book will be invaluable to any researcher, from the advanced undergraduate to the senior investigator, who is interested in these areas of plant cell biology.