Structures and Organelles in Pathogenic Protists (eBook)

Structures and Organelles in Pathogenic Protists 3
Preface 5
Reference 6
Contents 7
Contributors 9
The Mastigont System in Trichomonads 13
1 Introduction 14
2 The Mastigont System 14
2.1 Basal Bodies and Associated Filaments 16
2.1.1 Basal Body (kinetosomes) 16
2.1.2 Kinetosome R 18
2.1.3 Kinetosomes #1, #2, #3, #4 18
2.1.4 Clockwise Filaments 19
2.1.5 Sigmoidal Filaments 20
2.1.6 Supra-Kinetosomal Body or Supra-Basal Body 21
2.1.7 Infra-Kinetosomal Body or Infra-Basal Body 23
2.1.8 Marginal Lamella 23
2.2 Costa 23
2.2.1 Structure 23
2.2.2 Types of Costa 24
2.2.3 Association with Other Structures 24
2.2.4 Function and Motility 25
2.2.5 Chemical Composition 25
2.3 Comb 25
2.4 Axostyle and Pelta 26
2.4.1 Structure 26
2.4.2 Pelta 28
2.4.3 Functions 29
2.4.4 Stability 29
2.4.5 Movement 29
2.4.6 Composition 29
2.4.7 Association with Other Cell Structures 30
2.5 The Parabasal Filaments 30
2.6 Flagella 30
2.6.1 The Undulating Membrane 31
2.6.2 Flagellar Structure 31
2.6.3 Flagellar Movement 32
2.6.4 Flagellum Internalisation 33
3 The Spindle 33
3.1 The Atractophore 33
4 Centrin 35
5 Genome Sequence 36
References 36
Subpellicular Microtubules in Apicomplexa and Trypanosomatids 39
1 Introduction 6
2 Subpellicular Microtubules 41
2.1 In Trypanosomatids 42
2.2 In Apicomplexans 43
3 Visualization of the Whole Network of Subpellicular Microtubules 44
3.1 In Trypanosomatids 45
3.2 In Apicomplexans 45
4 High-Resolution Images of the Microtubules 49
4.1 In Trypanosomatids 49
4.2 In Apicomplexa 50
5 Immunocytochemical Characterization of the Microtubules 51
5.1 In Trypanosomatids 53
5.2 In Apicomplexa 55
6 Biochemistry 56
6.1 In Trypanosomatids 56
7 Drug Sensitivity 57
7.1 In Trypanosomatids 58
7.2 In Apicomplexa 58
8 Microtubule-Microtubule and Microtubule-Plasma Membrane Associations 58
8.1 In Trypanosomatids 59
8.2 In Apicomplexa 59
8.3 The Conoid in Apicomplexa 60
9 In Trypanosomatids 64
10 In Apicomplexans 64
11 Functional Data 65
11.1 In Trypanosomatids 66
11.2 In Apicomplexans 66
12 Perspectives 67
References 68
Flagellum Structure and Function in Trypanosomes 75
1 Introduction 76
2 The Structure of the Flagellum 77
3 The Basal Body 77
3.1 The Transition Zone 80
3.2 The Axoneme 81
3.3 The Paraflagellar Rod 82
4 Flagellar Positioning and Adhesion 83
5 Flagellum Construction 85
5.1 Trypanosome Cell Cycle 85
5.2 Intraflagellar Transport 89
6 Functions of a Motile Flagellum 91
6.1 Characteristics of Flagellum Motility 91
6.2 Flagellum Motility Contributes to Completion of Cell Division 92
6.3 Motility and Clearance of Surface Proteins 92
7 Conclusions and Perspectives 93
References 94
The Flagellar Pocket of Trypanosomatids: A Critical Feature for Cell Morphogenesis and Pathogenicity 99
1 Introduction 100
2 Physical Architecture of the Flagellar Pocket 101
2.1 New Insights Provided by Electron Tomography 103
3 Physical Organisation of the Flagellar Pocket and Dynamics of Operation 104
3.1 Entry of Macromolecules into the Flagellar Pocket: The ``Neck Channel´´ 104
3.2 Membrane Domains and Boundaries Within the Flagellar Pocket 107
4 The Role of the Flagellar Pocket in Immune Evasion 107
5 Life Cycle Differences in Size and Function of the Flagellar Pocket 109
6 Molecules Associated with the Flagellar Pocket 110
6.1 Proteins Involved in the Cytoskeletal Architecture of the Flagellar Pocket 111
6.2 Specific Receptors Located Within the Flagellar Pocket 112
6.2.1 TbHpHbR and Susceptibility of T. brucei to Lysis Human Serum 113
6.2.2 The Transferrin Receptor 114
6.2.3 Cysteine-Rich Repetitive Acidic Transmembrane Protein 115
7 Molecular Aspects of Endo/Exocytosis: Lessons from RNAi Mutants 116
7.1 Clathrin 116
7.2 Rab Proteins 117
7.3 Actin 118
7.4 Flagellum Proteins 118
7.5 Dynamin 119
8 The Flagellar Pocket: A Portal for Secretion of Large Polymeric Proteins 119
8.1 The Secretion of Proteophosphoglycans from the Flagellar Pocket of Leishmania 120
9 The Flagellar Pocket: An Example of Extreme Biology 121
References 121
Reservosomes of Trypanosoma cruzi 126
1 Introduction: Endocytosis in Higher Eukaryotic Cells 127
2 Endocytosis in Trypanosomatids 128
3 Endocytic Pathway in Trypanosoma cruzi 129
4 Reservosomes: A Historical View 130
5 Reservosome Morphological and Biochemical Characterization 131
6 Concluding Remarks 136
References 138
Megasomes in Leishmania 142
1 Introduction 143
1.1 Leishmaniasis and Leishmania 143
1.2 Leishmania Life Cycle and Differentiation 143
1.3 Molecular Aspects of Differentiation 144
1.4 Morphological Aspects and Markers of Differentiation 145
2 Secretory/Endocytic Pathway 146
2.1 Differentiation and the Secretory/Endocytic Pathways in Leishmania 146
2.2 Differentiation and the Secretory/Endocytic Pathways in Leishmania Amastigotes 147
2.3 Differentiation and the Secretory/Endocytic Pathways in Leishmania Promastigotes 147
3 Lysosomal Targeting 148
3.1 Lysosomal Targeting in Leishmania 149
4 Megasomes in Leishmania 150
4.1 Megasome Biogenesis 151
5 Lysosomes as Targets for Kinetoplastid Control 152
References 154
Organelles and Trafficking in Entamoeba histolytica 160
1 Introduction 161
2 Organelles and Protein Transport in E. histolytica 162
2.1 Mitosomes 162
2.2 Golgi/ER 164
2.3 Phagocytosis 168
2.4 Endocytosis 172
2.5 Rabs and Trafficking 173
3 Conclusions 175
References 175
Secretory Organelles in Apicomplexa 185
1 Introduction 186
2 Description 187
2.1 Identification 187
2.2 Molecular Characterization 188
2.2.1 Methods 188
2.2.2 Organelles Structure and Contents 188
3 Genesis 190
3.1 Morphological Studies 190
3.2 Molecular Details 190
4 Functions 191
4.1 Gliding Motility 191
4.2 Host Cell Invasion 192
4.2.1 Moving Junction 192
4.2.2 Parasitophorous Vacuole 194
4.3 Egress 194
4.4 Apical Binding 195
4.5 Cell Traversal 196
4.6 High-jacking Host Cell Functions 196
5 Exocytosis of Apicomplexa Secretory Organelles 197
6 Open Questions 200
7 Conclusion 200
References 201
Secretory Events During Giardia Encystation 205
1 Introduction 206
1.1 General Characteristics of the Parasite 206
2 Organelles and Machinery Involved in Protein Transport in Giardia lamblia 211
2.1 The Nuclear Envelope 211
2.2 The Endoplasmic Reticulum 213
2.3 The (elusive) Golgi Apparatus 216
2.4 The Peripheral Vacuoles 218
2.5 The Encystation-Specific Secretory Vesicles 219
2.6 The Cytoskeleton 222
3 The Encystation Process 223
3.1 General Characteristics 223
3.2 Encystation and Cyst Specific Molecules 224
3.3 Cyst Wall Assembly and Maturation 227
4 Concluding Remarks 230
References 230
The Remarkable Mitochondrion of Trypanosomes and Related Flagellates 236
1 The Kinetoplast DNA 237
1.1 kDNA: Its In vivo Structure and Diversity 238
1.2 Maxicircles 239
1.3 Minicircles 241
1.4 Replication and Maintenance of kDNA 241
2 RNA Editing 243
2.1 Mechanism of RNA Editing 243
2.2 The RNA Editing Core Complex 244
2.3 Other Proteins Involved in RNA Editing and/or Processing 245
2.4 The raison d'etre of RNA Editing 246
3 The Mitochondrial RNA Metabolism 247
4 Mitochondrial Transfer RNAs 248
5 Mitochondrial-Encoded Proteins 249
5.1 Mitochondrial Translation in T. brucei 249
5.2 Composition of Mitochondrial Respiratory Complexes 250
6 Energy Metabolism of the T. brucei Mitochondrion 253
6.1 Bloodstream Stage 253
6.2 Procyclic Stage 254
References 255
The Apicoplast: An Ancient Algal Endosymbiont of Apicomplexa 262
1 The Surprising Photosynthetic Past of Apicomplexa 263
1.1 The Discovery of the Apicoplast: From Vacuole to Endosymbiont 264
1.2 The Apicoplast´s Endosymbiotic Origin is the Source of Its Complex Biology 265
1.3 The Apicoplast Genome is Mostly Concerned with Itself 267
2 The Long Journey from Nucleus to Apicoplast 268
2.1 A Bipartite Leader Peptide is Required for Apicoplast Targeting 268
2.2 Chloroplast Derived Membranes are Crossed Using Chloroplast Translocons 269
2.3 Retooling an Endosymbiont Translocon from Export to Import 271
2.4 Still a Black Box: How Do Apicoplast Proteins Find the Apicoplast? 272
2.5 Additional Signals and Mechanisms may be Involved in the Trafficking of Apicoplast Membrane Proteins 273
3 Replicating and Dividing the Apicoplast 274
3.1 The Apicoplast Genome is Replicated by Prokaryotic-Type Machinery 274
3.2 Organelle Division and Segregation: Fission with a Twist 275
4 What are the Metabolic Functions of the Apicoplast? 276
4.1 Type II Fatty Acid Biosynthesis (FASII): A Slippery Target 277
4.2 Prokaryotic Isoprenoid Biosynthesis: The Pathway Found in All Apicoplasts 279
4.3 Heme Biosynthesis has Many Homes and Remains to be Fully Characterized 281
4.4 Apicoplast Transporters: Feeding a Chloroplast in the Dark 282
5 Conclusions 283
References 283
The Glycosome of Trypanosomatids 293
1 Introduction 294
2 Discovery of the Glycosome 294
3 Glycosomes in Other Members of the Kinetoplastida 295
4 Morpholgy and Properties of the Organelle 296
5 Biogenesis of Glycosomes 297
6 Metabolic Pathways Associated with Glycosomes 298
6.1 Glycolysis 298
6.2 Gluconeogenesis 298
6.3 Pentosephosphate Shunt 300
6.4 Lipid Metabolism 300
6.4.1 Fatty Acid Oxidation 300
6.4.2 Ether-Lipid Synthesis 301
6.4.3 Sterol Synthesis 301
6.5 Nucleotide Metabolism 301
7 Conclusions 303
References 303
Calcium Homeostasis and Acidocalcisomes in Trypanosoma cruzi 307
1 Introduction 308
2 Cytosolic Ca2+ Concentration and the Role of the Plasma Membrane 309
3 Ca2+-Binding Proteins 310
4 Ca2+ and Cell Signaling 312
5 Calcium Storage Compartments 315
5.1 Endoplasmic Reticulum 315
5.2 Nucleus 317
5.3 Mitochondria 318
5.4 Acidocalcisomes 318
6 Ca2+ Functions in T. cruzi 322
6.1 Invasion of the Host Cell and Differentiation 322
7 Conclusions 322
References 323
Index 327