International Review of Cytology (eBook)

A Survey of Cell Biology

Kwang W. Jeon (Herausgeber)

eBook Download: EPUB

2007 | 1. Auflage
256 Seiten
Elsevier Science (Verlag)
978-0-08-047506-6 (ISBN)

Infos

International Review of Cytology presents current advances and comprehensive reviews in cell biology - both plant and animal. Authored by some of the foremost scientists in the field, each volume provides up-to-date information and directions for future research. This volume contains articles on Mechanism of Depolymerization and Severing of Actin Filaments and Its Significance in Cytoskeletal Dynamics, Biology of Polycomb and Thrithorax Group Proteins, Cell and Molecular Biology of Transthyretin and Thyroid Hormones, and Development and Role of Tight Junctions in the Retinal Pigment Epithelium.

Inhalt

Cover 1
Copyright Page 5
Contents 6
Contributors 8
Chapter 1: Mechanism of Depolymerization and Severing of Actin Filaments and Its Significance in Cytoskeletal Dynamics 9
I. Introduction 9
II. Proteins That Depolymerize and/or Sever Actin Filaments 10
A. Gelsolin and Gelsolin-Related Proteins 10
B. ADF/Cofilin 21
C. Actin-Interacting Protein 1 32
D. Other Proteins 34
III. Cell Biological Significance of Actin Depolymerization and Severing 36
A. Cell Viability 36
B. Cell Migration 37
C. Cytokinesis 41
D. Actin-Based Motility of Pathogenic Bacteria 43
E. Membrane Trafficking 44
F. Myofibril Assembly and Maintenance 48
G. Nuclear Functions 51
IV. Concluding Remarks 53
Acknowledgments 54
References 54
Chapter 2: Biology of Polycomb and Trithorax Group Proteins 91
I. Introduction 91
II. PcG, trxG, and Their Protein Complexes 93
A. Genetics of PcG and trxG Members 93
B. PcG and trxG Protein Complexes 95
III. Epigenetic Regulation of Gene Expression by PcG and trxG Proteins 98
A. PcG and trxG Complexes Binding Specialized DNA Elements: PREs 98
B. PcG Complexes and Their Targets 100
C. Mechanisms of Epigenetic Transmission 103
D. Epigenetic Marks: How Memory Is Kept 115
IV. Targets of Maintenance Complexes 118
A. Hox Genes and Developmental Regulators 118
B. PcG Complexes in Cell Cycle Regulation, Hematopoiesis, and Stem Cell Maintenance 120
V. Roles for PcG Complexes in DNA Methylation, X.Inactivation, and Genomic Imprinting 123
A. DNA Methylation 123
B. X Inactivation and Genomic Imprinting 125
VI. Conclusions and Perspectives 126
References 128
Chapter 3: Cell and Molecular Biology of Transthyretin and Thyroid Hormones 145
I. Introduction 146
II. Transthyretin and Thyroid Hormones 147
A. Thyroid Hormone Distributor Proteins 147
B. Transthyretin 148
C. Transthyretin Structure 149
D. Binding of Thyroid Hormones and Other Ligands to Transthyretin 151
III. Transthyretin Gene and Transthyretin Synthesis 155
A. Transthyretin Gene Structure and Its Evolution in Vertebrates 155
B. Sites of Transthyretin Synthesis in Mammals 157
C. Tissue-Specific Regulation of Transthyretin Gene 159
IV. Regulation of Transthyretin Gene 161
A. Transthyretin Gene Regulation During Development 161
B. Transthyretin Gene Regulation During Evolution 165
V. Evolution of Transthyretin Structure and Function in Vertebrates 172
A. Three-Dimensional Structure 172
B. Primary Structure 172
C. N-Terminal Region of Subunit 175
D. Transthyretins from Fish, Amphibians, Reptiles, and Birds 175
E. Possible Implications of Changing from Binding T3 to Binding T4 179
VI. Additional Features of Transthyretins 180
A. Transthyretin and Human Diseases 180
B. Transthyretin Null Mice 183
C. Transthyretin-Like Proteins in Nonvertebrate Species 186
VII. Concluding Remarks 188
References 191
Chapter 4: Development and Role of Tight Junctions in the Retinal Pigment Epithelium 203
I. Introduction 203
II. General Properties of Retinal Pigment Epithelium 205
A. Comparison of RPE with Other Regions of the Blood-Brain Barrier 205
B. Transport Across the RPE Monolayer 207
III. Protein Composition and Assembly of Tight Junctions 212
A. Protein Composition 212
B. Development of RPE and Assembly of Tight Junctions 218
IV. Tissue Interactions That Regulate Tight Junctions 224
A. Interactions That Affect the Basic Epithelial Phenotype 224
B. Digression on the Effects of Culture Media on RPE Tight Junctions 226
C. Interactions Between Chick RPE and the Neural Retina 231
D. Basal Interactions of Chick RPE and the Potential for Choroidal-Retinal Synergism 234
V. Concluding Remarks 235
Acknowledgments 236
References 236
Index 243

Textauszug

Mechanism of Depolymerization and Severing of Actin Filaments and Its Significance in Cytoskeletal Dynamics

Shoichiro Ono    Department of Pathology, Emory University, Atlanta, Georgia 30322

Abstract

The actin cytoskeleton is one of the major structural components of the cell. It often undergoes rapid reorganization and plays crucial roles in a number of dynamic cellular processes, including cell migration, cytokinesis, membrane trafficking, and morphogenesis. Actin monomers are polymerized into filaments under physiological conditions, but spontaneous depolymerization is too slow to maintain the fast actin filament dynamics observed in vivo. Gelsolin, actin‐depolymerizing factor (ADF)/cofilin, and several other actin‐severing/depolymerizing proteins can enhance disassembly of actin filaments and promote reorganization of the actin cytoskeleton. This review presents advances as well as a historical overview of studies on the biochemical activities and cellular functions of actin‐severing/depolymerizing proteins.

Key words

Actin dynamics

Gelsolin

ADF/cofilin

AIP1

Cytoskeleton

I Introduction

Actin is one of the major cytoskeletal components in most eukaryotic cells and supports not only the structural integrity of the cell, but also dynamic cellular events such as cell movement, cytokinesis, and even gene expression. Actin is a conserved 42‐kDa protein that can be spontaneously polymerized into a polar filament in vitro under physiological conditions. Actin polymerizes only when a concentration of monomer (or globular [G‐] actin) is higher than the critical concentration (Oosawa, 2001; Sheterline et al., 1998). However, the critical concentration at the minus (or pointed) end (∼0.6 μM) is higher than that at the plus (or barbed) end (∼0.1 μM). As a result, at a steady state, actin subunits are constantly depolymerized from the minus ends and added to the plus ends. This phenomenon is called actin treadmilling (Cleveland, 1982; Neuhaus et al., 1983). Actin treadmilling occurs in the actin filaments in living cells (Wang, 1985) and is considered to be one of the major mechanisms of actin filament turnover in vivo (Carlier et al., 2003; Pantaloni et al., 2001; Pollard and Borisy, 2003). However, the rates of actin turnover in living cells are 20–100 times faster than those of purified actin in vitro (Theriot and Mitchison, 1991; Wang, 1985). This is primarily because the off rate of actin subunits from the minus end is slow and becomes the rate‐limiting step in treadmilling, whereas association of actin monomers with exposed plus ends or de novo nucleation sites is relatively fast (Pollard, 1986; Wegner and Isenberg, 1983). To accelerate actin turnover, depolymerization of actin from the minus ends needs to be enhanced, or the number of filament ends needs to be increased by filament severing. Thus, depolymerization and severing of actin filaments are critical for regulating actin cytoskeletal dynamics, as well as actin nucleation, filament capping, nucleotide exchange, and monomer sequestration (Carlier et al., 2003; Pantaloni et al., 2001; Pollard and Borisy, 2003; Pollard et al., 2001). This review covers the mechanism of depolymerization and severing of actin filaments, which is currently known to be mediated by two major classes of actin‐binding proteins: gelsolin (Fig. 1A–C) and actin‐depolymerizing factor (ADF)/cofilin (Fig. 1D). In addition, actin‐interacting protein 1 (AIP1) is a protein that promotes actin filament disassembly in cooperation with ADF/cofilin (Fig. 1F). Actin‐severing or ‐depolymerizing activity has also been reported for twinfilin (Fig. 1E), coronin (Fig. 1G), a formin‐related protein (Fig. 1H), cyclase‐associated protein (Fig. 1I), and DNase I (Fig. 1J).

Fig. 1 Domain structures of actin‐severing/depolymerizing proteins. (A) Fragmin/severin. (B) Gelsolin/adseverin (scinderin). (C) Villin. (D) ADF/cofilin. (E) Twinfilin. (F) Actin‐interacting protein 1. (G) Coronin. (H) Formin. (I) Cyclase‐associated protein. (J) DNase I. Representative domains of the proteins discussed in this article are shown schematically. N termini are to the left.

II Proteins That Depolymerize and/or Sever Actin Filaments

A Gelsolin and Gelsolin‐Related Proteins

1 Gelsolin Family

The gelsolin family of actin‐binding proteins is one of the major classes of actin‐severing proteins (Kwiatkowski, 1999; McGough et al., 2003; Silacci et al., 2004; Sun et al., 1999). Gelsolin was originally discovered in macrophages as a factor inducing the gel–sol transformation of actin filaments in a calcium‐dependent manner (Yin and Stossel, 1979). Gelsolin and gelsolin‐related proteins are widely present in metazoan species but are not found in yeast. Further biochemical characterization of gelsolin revealed that gelsolin binds to calcium, severs actin filaments, and caps the plus ends (Yin and Stossel, 1980; Yin et al., 1980, 1981b).

A number of proteins with similar calcium‐dependent actin‐severing activity were discovered in the early to mid‐1980s in various sources and designated by different names (Maruyama, 1986; Pollard and Cooper, 1986; Stossel et al., 1985). These include fragmin from Physarum (slime mold) (Hasegawa et al., 1980) (also known as actin‐modulatory protein [Hinssen, 1981a,b]), villin from intestinal brush border (Bretscher and Weber, 1980; Craig and Powell, 1980; Glenney et al., 1981b), severin from Dictyostelium (Brown et al., 1982; Yamamoto et al., 1982), brevin from rabbit serum (Harris and Schwartz, 1981) (also known as plasma F‐actin‐depolymerizing factor [Thorstensson et al., 1982]), a 45‐kDa protein (Coluccio et al., 1986; Hosoya and Mabuchi, 1984; Ohnuma and Mabuchi, 1986; Wang and Spudich, 1984) and a 100‐kDa protein from sea urchin egg (Hosoya et al., 1986), and 88‐ to 93‐kDa proteins from various vertebrate tissues (Ebisawa and Nonomura, 1985; Nishida et al., 1983; Petrucci et al., 1983; Wang and Bryan, 1981). Plants also have gelsolin‐like actin‐severing proteins (Fan et al., 2004; Huang et al., 2004; Yamashiro et al., 2001). However, a villin‐like protein in Arabidopsis does not sever actin filaments (Huang et al., 2005).

As discussed in greater detail later (Section II.A.2), determination of the primary structure of gelsolin revealed that it has six homologous domains of 100–120 amino acids, which are termed gelsolin‐like (G) domains 1–6 (Fig. 1B) (Kwiatkowski et al., 1986). Interestingly, cytoplasmic and secreted plasma isoforms of gelsolin (brevin or plasma F‐actin‐depolymerizing factor) are encoded by a single gene (Kwiatkowski et al., 1986, 1988). Subsequent sequence analyses of other calcium‐dependent actin‐severing proteins showed that the 40‐ to 45‐kDa proteins including fragmin (Ampe and Vandekerckhove, 1987) and severin (Andre et al., 1988; Schleicher et al., 1988) have three G domains, whereas other 85‐ to 100‐kDa proteins have six G domains (Fig. 1A–C) (Arpin et al., 1988; Bazari et al., 1988; Way and Weeds, 1988). Villin has an 8.5‐kDa C‐terminal headpiece domain in addition to six G domains (Fig. 1C) (Arpin et al., 1988; Bazari et al., 1988). The villin headpiece domain has calcium‐independent F‐actin‐binding activity and confers to villin its unique actin‐bundling activity (Glenney et al., 1981a). Vertebrates also have two additional gelsolin isoforms: adseverin (Ashino et al., 1987; Maekawa et al., 1989; Nakamura et al., 1994) (also known as scinderin [Rodriguez Del Castillo et al., 1990; Trifaro et al., 2000]) and gelsolin‐3 (Vouyiouklis and Brophy, 1997) and a villin isoform, advillin (Marks et al., 1998). A splice variant of adseverin that has only five G domains is expressed in blood cells (Robbens et al., 1998).

Other unconventional gelsolin‐related proteins have also been reported. CapG (also known as macrophage‐capping protein [Dabiri et al., 1992; Southwick and DiNubile, 1986], Mbh1 [Prendergast and Ziff, 1991], or gCap39 [Yu et al., 1990]) has three G domains and caps the plus ends of actin...

Produkt-Details

• Erscheint lt. Verlag: 28.2.2007
• Sprache: englisch
• Themenwelt: Sachbuch/Ratgeber
• Themenwelt: Studium ► 1. Studienabschnitt (Vorklinik) ► Histologie / Embryologie
• Themenwelt: Studium ► 1. Studienabschnitt (Vorklinik) ► Physiologie
• Themenwelt: Naturwissenschaften ► Biologie ► Genetik / Molekularbiologie
• Themenwelt: Naturwissenschaften ► Biologie ► Zellbiologie
• Themenwelt: Naturwissenschaften ► Biologie ► Zoologie
• Themenwelt: Technik
• ISBN-10: 0-08-047506-X / 008047506X
• ISBN-13: 978-0-08-047506-6 / 9780080475066