International Review of Cytology (eBook)

A Survey of Cell Biology

Kwang W. Jeon (Herausgeber)

eBook Download: EPUB

2007 | 1. Auflage
296 Seiten
Elsevier Science (Verlag)
978-0-08-047114-3 (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.

Inhalt

Front Cover 1
A Survey of Cell Biology 4
Copyright Page 5
Contents 6
Contributors 10
Chapter 1: Metabolism and Metabolomics of Eukaryotes Living Under Extreme Conditions 12
I. Introduction 13
II. Eukaryotic Extremophiles 14
III. Metabolic Analysis and Adaptations of Extremophiles 19
IV. Genomics and Metabolomics Working Hand in Hand 31
V. Conclusions and Perspectives 34
Acknowledgments 35
References 35
Chapter 2: Transient Receptor Potential Channels and Intracellular Signaling 46
I. Introduction 46
II. TRP Channel Superfamily 48
III. Activation Mechanisms 53
IV. Physiological Functions of TRP Channels 58
V. Concluding Remarks 67
References 67
Chapter 3: Multiple Functions of the Origin Recognition Complex 80
I. Introduction 81
II. Eukaryotic Origins and Discovery of the Origin Recognition Complex 81
III. ORC Functions in DNA Replication 84
IV. Nonreplicative Functions of the ORC 100
V. Concluding Remarks 111
Acknowledgments 112
References 112
Chapter 4: Auxin-Mediated Lateral Root Formation in Higher Plants 122
I. Introduction 122
II. Lateral Root Development in Arabidopsis 124
III. Lateral Root Mutants in Other Plant Species 137
IV. Concluding Remarks and Perspectives 140
Acknowledgments 141
References 141
Chapter 5: MHC Class I Antigens and Immune Surveillance in Transformed Cells 150
I. Introduction 150
II. MHC Class I: Genes, Protein Structure, and Expression in Normal Tissues 152
III. Cellular Machinery of Antigen Presentation to T Lymphocytes 156
IV. Interaction of MHC Class I Molecules with T Lymphocytes and NK Cells 160
V. Immune Response Against Cancer Cells 164
VI. Tumor Progression 177
VII. Concluding Remarks 185
Acknowledgments 186
References 186
Chapter 6: Daylength Measurements by Rice Plants in Photoperiodic Short-Day Flowering 202
I. Introduction: History of Studies on Photoperiodic Flowering Before Molecular Cloning 202
II. Photoperiodic Flowering in Plants 204
III. Photoperiodic Responses 218
IV. Concluding Remarks 228
References 228
Chapter 7: Glutamatergic Functions of Primary Afferent Neurons with Special Emphasis on Vagal Afferents 234
I. Introduction 234
II. Historical Overview on Glutamatergic Transmission Mechanisms 236
III. Vesicular Glutamate Transporters (VGLUT1-3) 239
IV. Intraganglionic Laminar Endings 243
V. VGLUTs in Peripheral Terminals of Primary Afferent Neurons 253
VI. Distribution of Glutamate Receptors in the Peripheral Nervous System 264
VII. Functional Hypotheses on the Local Effector Role of IGLEs 268
VIII. Concluding Remarks 273
References 274
Index 288

Textauszug

Transient Receptor Potential Channels and Intracellular Signaling

Geoffrey E. Woodard*; Stewart O. Sage†; Juan A. Rosado‡    * Metabolic Diseases Branch, NIDDK, National Institutes of Health, Bethesda, Maryland
† Department of Physiology, Development, and Neuroscience, University of Cambridge, Cambridge, United Kingdom
‡ Department of Physiology, University of Extremadura, Cáceres, Spain

Abstract

The transient receptor potential (TRP) family of ion channels is composed of more than 50 functionally versatile cation-permeant ion channels expressed in most mammalian cell types. Considerable research has been brought to bear on the members of this family, especially with regard to their possible role as store-operated calcium channels, although studies have provided evidence that TRP channels exhibit a number of regulatory and functional aspects. Endogenous and transiently expressed TRP channels can be activated by different mechanisms grouped into four main categories: receptor-operated activation, store depletion-mediated activation, ligand-induced activation, and direct activation. This article reviews the biochemical characteristics of the different members of the TRP family and summarizes their involvement in a number of physiological events ranging from sensory transduction to development, which might help in understanding the relationship between TRP channel dysfunction and the development of several diseases.

Key words

TRP

Calcium signaling

Cation channels

Calcium entry

Cell physiology

I Introduction

The transient receptor potential (TRP) proteins are six transmembrane domain-containing subunits that form cation-selective ion channels. The TRP superfamily includes at least 22 related channels that play an important role in a number of cellular functions ranging from sensory transduction (including invertebrate vision, temperature, pain, and gustatory and osmolarity detection) to development. The first member of the TRP superfamily was identified as a protein involved in phototransduction in Drosophila. The transient receptor potential (trp) gene was named on the basis of the transient, rather than sustained, response to light in mutant flies. From the beginning a relationship between TRP proteins and ionic currents across the membrane was suggested since trp mutants displayed a defect in light-induced Ca2+ influx, which together with the predicted structure of TRP and the related protein, TRPL, raised the possibility that these proteins were Ca2+ influx channels (Montell et al., 2002a).

TRP proteins are present in yeast, Drosophila, Caenorhabditis elegans, and mammals. TRP channels are widely expressed in both excitable and nonexcitable cells, and TRP-related channels have been proposed as candidates to mediate Ca2+ entry. Although all TRP proteins form cation channels these differ significantly in their selectivity and activation mechanisms, although most members of the TRP superfamily share significant sequence homology.

TRP-related channels can be grouped into three subfamilies: those most closely related to TRP (TRPC, TRPV, and TRPM), two subfamilies that are more distantly related to TRP (TRPP and TRPML), and a less related TRPN group that is expressed in flies and worms and includes the mechanosensory channel NOMPC (Montell et al., 2002b). The TRPC subfamily encompases the mammalian proteins that display the greatest similarity to Drosophila TRP, sharing between 32 and 47% amino acid homology over the N-terminal 800 amino acids, including three or four ankyrin repeats, the six transmembrane domains, and a highly conserved 25 amino acid sequence known as the TRP box. TRPV proteins also include three or four ankyrin domains but lack the TRP box, and TRPM proteins contain a TRP box, but no ankyrin repeats (Montell et al., 2002b).

Most TRP channels are nonselective for monovalent and divalent cations with Ca2+ to Na+ permeability ratios (PCa/PNa) of ≤10. Exceptions are TRPM4 and TRPM5, which are selective for monovalent cations, and the Ca2+-selective TRPV5 and TRPV6, which have a PCa/PNa > 100. In contrast to voltage-gated channels, TRP channels lack the voltage sensitivity of the 24 membrane-spanning CaV or NaV families. Therefore, TRP channel opening induces membrane depolarization from the resting membrane potential (about −70 mV in most mammalian cells) to around 0 mV while increasing cytosolic Ca2+ and/or Na+ concentrations (Clapham et al., 2003). This article presents an overview of the structure and molecular relationships among the TRP channels and their role in physiological cell processes.

II TRP Channel Superfamily

A TRP Channel Structure and Functional Features

All members of the TRPC family are believed to share a common architecture. The analysis of the structure of TRP proteins reveals that these proteins contain six transmembrane domains, with cytoplasmic N- and C-termini, and a pore region between the transmembrane domains 5 and 6 (Hoenderop et al., 2003). However, in comparison with other ionic channels little is known about the architecture of the TRP channels or the structural organization of the pore region, responsible for the selectivity of the channels. The N-terminus contains three to four ankyrin repeats, a predicted coiled coil region, and a putative caveolin-binding domain. On the other hand, the C-terminus includes the TRP signature motif (EWKFAR), a proline-rich motif, the calmodulin/inositol 1,4,5-trisphosphate (IP3) receptor-binding (CIRB) domain, and a predicted coiled-coil region. TRPC4 and TRPC5 also contain a PDZ-binding motif in the C-terminus (Dohke et al., 2004; Montell, 2001; Vannier et al., 1998; Vazquez et al., 2004).

The ankyrin repeat is one of the most frequently observed amino acid motifs. This protein–protein interaction module is involved in a number of cellular functions. However, unlike other binding domains, ankyrin repeats do not recognize a conserved sequence or structure, but in contrast can bind to a variety of domains making it difficult to predict possible binding partners for the TRPC ankyrin repeats (Vazquez et al., 2004). The ankyrin repeats appear to be required for correct location of TRPC3 (Wedel et al., 2003) and TRPC6 (Hofmann et al., 2002) in the plasma membrane. However, the requirement of all ankyrin repeats for functional expression of TRP channels deserves further investigation, since for some TRP channels, such as the TRPC1, a splice variant missing certain ankyrin repeats (TRPC1A) forms a Ca2+-permeable cation channel activated by depletion of intracellular Ca2+ stores (Zitt et al., 1996).

The cytoplasmic N- and C-termini also contain a coiled-coil motif, which consists of several heptad repeats folding into an α-helix, which, by association with other α-helices, forms a supercoil. Coiled-coil motifs are commonly involved in protein oligomerization (Woolfson, 2005), therefore these domains might contribute to homo- and heteromerization of TRP channels or the association of TRP proteins with other coiled-coil motif-containing proteins (Vazquez et al., 2004). Consistent with this, coiled-coil motifs in the N-terminus of TRPC1 have been shown to homodimerize (Engelke et al., 2002). In TRPC1, calmodulin binding to the coiled-coil domain has been demonstrated and the deletion of this domain resulted in diminished Ca2+-dependent inactivation of store-operated Ca2+ entry (Singh et al., 2002).

As previously mentioned, TRP proteins contain a caveolin-binding domain in the N-termini, close to the first transmembrane domain, which allows them to associate with specific plasma membrane microdomains called caveolae. The association of TRPC1 and TRPC3 with caveolins has been demonstrated (Brazer et al., 2003; Lockwich et al., 2001) and deletion of this motif in TRPC1 results in the loss of targeting to the plasma membrane.

There is great variability in the permeation properties of different members of the TRP superfamily. There are channels, such as TRPV1, that are rather nonselective for mono- and divalent cations (Caterina et al., 1997), TRP channels, including TRPM4 and TRPM5, permeable to monovalent cations and impermeable to Ca2+ (Hofmann et al., 2003; Launay et al., 2002), and TRP channels that show a high selectivity for Ca2+ over monovalent cations, including TRPV5 and TRPV6 (Vennekens et al., 2000; Yue et al., 2001). This variability contrasts with most other families of ion channels, where the differences in pore permeability within one family are generally small. Although functional studies have been published of all TRPCs and TRPVs and of most TRPMs (Clapham et al., 2001; Montell et al., 2002a), reporting that these proteins operate as cation channels, a systematic analysis of the pore region of TRP channels has not yet been carried out. It is generally accepted that demonstrations that specific mutations in the putative pore domain of the candidate channel protein alter the pore properties, such as ion selectivity and conductance, provides compelling...

Produkt-Details

• Erscheint lt. Verlag: 2.2.2007
• Sprache: englisch
• Themenwelt: Sachbuch/Ratgeber
• Themenwelt: Studium ► 1. Studienabschnitt (Vorklinik) ► Histologie / Embryologie
• Themenwelt: Naturwissenschaften ► Biologie ► Genetik / Molekularbiologie
• Themenwelt: Naturwissenschaften ► Biologie ► Zellbiologie
• Themenwelt: Technik
• ISBN-10: 0-08-047114-5 / 0080471145
• ISBN-13: 978-0-08-047114-3 / 9780080471143