Jeon International Review of Cell and Molecular Biology

1. Auflage 2010
ISBN: 978-0-12-381255-1
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 283, 352 Seiten

Reihe: International Review of Cell and Molecular Biology

International Review of Cell and Molecular Biology presents current advances and comprehensive reviews in cell biology--both plant and animal. Articles address structure and control of gene expression, nucleocytoplasmic interactions, control of cell development and differentiation, and cell transformation and growth. Impact factor for 2008: 4.935. - Authored by some of the foremost scientists in the field - Provides up-to-date information and directions for future research - Valuable reference material for advanced undergraduates, graduate students and professional scientists

Autoren/Hrsg.

Jeon, Kwang W.

Leseproben

Chapter Two New Insights into the Dynamics of Cell Adhesions
Patricia Costa; Maddy Parsons    Randall Division of Cell and Molecular Biophysics, King's College London, New Hunts House, Guys Campus, London, United Kingdom Abstract
Adhesion to the extracellular matrix (ECM) and to adjacent cells is a fundamental requirement for survival, differentiation, and migration of numerous cell types during both embryonic development and adult homeostasis. Different types of adhesion structures have been classified within different cell types or tissue environments. Much is now known regarding the complexity of protein composition of these critical points of cell contact with the extracellular environment. It has become clear that adhesions are highly ordered, dynamic structures under tight spatial control at the subcellular level to enable localized responses to extracellular cues. However, it is only in the last decade that the relative dynamics of these adhesion proteins have been closely studied. Here, we provide an overview of the recent data arising from such studies of cell–matrix and cell–cell contact and an overview of the imaging strategies that have been developed and implemented to study the intricacies and hierarchy of protein turnover within adhesions. Key Words Cell adhesion Extracellular matrix Integrin Cadherin Cytoskeleton Signaling Microscopy Dynamics 1 Introduction
Cell adhesion to other cells and/or to the extracellular matrix (ECM) is a fundamental requirement for normal embryonic development, adult homeostasis, and immune functions (Reddig and Juliano, 2005; Wozniak et al., 2004). The cell structures that mediate interactions with ECM can take a number of different forms depending upon both the cell type and the tissue environment. The protein composition, localization, and proteolytic capabilities of these so-called adhesion complexes all contribute to the classification and function of the structure. Cell–cell adhesion classically plays a role in the stability and integrity of both epithelial and endothelial cell layers. While the structure and components of cell–cell adhesive contacts are broadly different to cell–ECM adhesions, both share a large number of common signaling mediators that are responsible for regulating formation, maintenance, and dynamics. Cell adhesion is required for normal development in many different tissues, in the context of formation of specific tissue compartments, maintenance of barrier function, and cell migration. In many cases, these adhesive structures are not static but rather they undergo dynamic changes in composition and structure to enable the cells to respond to changing extracellular cues. The regulation of such dynamic changes is under tight spatial and temporal control by numerous signaling proteins that can dictate the type, location, and duration of adhesive contact formed. Recent progress in microscopic techniques has enabled closer observation and dissection of these fundamental events. Here, we will provide an overview of some of the strategies used to study these dynamic transient events in live cells, and review some of the recent findings in this field. 2 Overview of Cell Adhesion
2.1 Types of cell-adhesion structures
2.1.1 Cell–matrix adhesions The adhesion structures that form between a cell and ECM can take a number of different forms, ranging from classical focal adhesions (FAs) to podosomes and invadopodia. The classification of these structures is based upon several factors, including localization, proteolytic capability, and protein composition. At least 150 different proteins have been found to be involved with the formation, maintenance, and disassembly of these various adhesion structures (Zaidel-Bar et al., 2007) and for recent reviews see Dubash et al. (2009), Harburger and Calderwood (2009), and Vicente-Manzanares et al. (2009). The integrin family of heterodimeric transmembrane receptors are important in the initiation and stability of all types of adhesive structure. With both extracellular and intracellular domains, these receptors have the unique ability to bind the ECM and recruit proteins to their cytoplasmic face, thereby linking the cell exterior to interior. Actin-binding proteins such as talin, filamin, and a-actinin are recruited to the cytoplasmic tail of the integrin receptor upon ECM binding and are able to form direct links to the actin cytoskeleton to initiate stress fibers and thus providing a mechanical scaffold (Albiges-Rizo et al., 2009). Each protein recruited to the integrin tail is also in turn able to recruit other specific binding partners to the point of adhesion. Adaptor proteins and kinases such as Src and focal adhesion kinase (FAK) are among the proteins that are recruited, each playing their part in the adhesion signaling cascade and assisting in determining the lifespan of the structure. Integrins are not the only family of receptors involved with adhesion signaling. Syndecans are a family of heparan sulfate proteoglycans that can bind directly to ECM and soluble extracellular growth factors. Syndecans can also act in synergy with integrins, assisting in the recruitment of proteins to adhesion sites (Morgan et al., 2007). Recent evidence has shown that syndecan-4 controls recruitment of protein kinase C (PKC) and subsequent downstream control of the GTPase Rac in cooperation with a5ß1 integrin (Bass et al., 2007). Early studies revealed that different types of adhesive structures can exist in a single cell at any one time (Izzard and Lochner, 1980). Three classical structures initially described in these studies were focal complexes (FCs), FAs, and fibrillar adhesions (FBs), each having their own specific characteristics (Puklin-Faucher and Sheetz, 2009; Zaidel-Bar et al., 2004, 2007). FCs are small, transient structures, typically located behind the leading edge of a spreading or migrating cell (Figs. 2.1A and 2.2B). These are short-lived structures, assembling and disassembling in the order of minutes and are said to “sample” the local ECM before disassembling or moving on to form more stable structures. FAs are both larger and more stable structures than FCs and in some cases are formed by maturation of a preexisting FC. These adhesions contain multiple proteins, ensuring stability of the adhesion and that traction forces are transmitted from the ECM and vice versa and as such have lifetimes in the order of tens of minutes. FBs are long, stable structures that run parallel to bundles of fibronectin (FN) in vivo and are highly enriched in tensin and a5ß1 integrin (Fig. 2.1A; Green and Yamada, 2007). These adhesive structures are also sites of localized matrix deposition and FN fibrillogenesis. Although the molecular composition of these adhesions share similarities, studies have shown there are also subtle differences among them, for example, zyxin is not found in FCs and ß3 integrin is not found in FBs (Cukierman et al., 2001; Zaidel-Bar et al., 2003). Our knowledge of these structures is by no means complete and as such further studies will be required to explain how these differences in protein composition are regulated. Figure 2.1 Adhesion types and localization. (A) General composition and localization of focal complexes and focal adhesions (top image) and matrix-associated fibrillar adhesions (bottom cell). (B) Localization of invadopodia (top cell) and podosomes (bottom cell). (C) General composition and localization of tight junctions, adherens junction, desmosomes, hemidesmosomes, and focal adhesions found in cells in contact (such as epithelial or endothelial cells). Figure 2.2 Adhesion dynamics. (A) Formation of junctions between opposing epithelial cells. Contacts are initiated through formation of actin-based lamellipodia (top) followed by homodimerization between opposing E-cadherin molecules (middle) and subsequent acto-myosin-dependent adhesion belt strengthening (bottom). (B) Focal adhesion dynamics. Focal adhesions are formed between cell and ECM and stabilized by actin stress fibers (top panels). Upon cells membrane extension and protrusion, nascent adhesion complexes are formed beneath the leading edge (middle) and this is coupled to disassembly of adhesions at the rear (bottom) to enable acto-myosin-dependent rear edge retraction and cell movement. Two other classes of cell–ECM adhesion structures, podosomes and invadopodia differ further in their ability to act as local ECM degradation sites by recruiting matrix metalloproteinases (MMPs; Fig. 2.1B). Podosomes typically appear in cells of monocytic origin, such as macrophages, or osteoclasts, whereas invadapodia appear in malignant cells (Linder, 2007). Podosomes are composed of cores of F-actin and actin-binding proteins such as cortactin within a ring of integrins. Typically, ß1 integrins are localized to the core of these structures when ß2, ß3, and vinculin localize to the ring (Fig. 2.1B). Although the protein composition of these podosomes and invadopodia are similar, one difference between appears to be that invadopodia are more punctate, finger-like...