7.6.3
Dynamic Instability: Different Behavior of Plus
and Minus Ends in Polymerization/Depolymerization
Episode of Microtubule . . . . . . . . . . . . . . . . . . . . . . . . 119
7.6.4
Catastrophe and Rescue . . . . . . . . . . . . . . . . . . . . . . . . 119
7.7
Cell Motility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
7.8
Extracelluar Matrix and Its Connection to Cytoskeleton . . . . . . . . 121
7.9
Cell Membrane and Membrane Skeleton . . . . . . . . . . . . . . . . . . 121
7.10 Lamllipodia and Filopodia: Protrusive Membranous Structures
of the Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
7.11 Actin Stress Fiber and Focal Adhesion . . . . . . . . . . . . . . . . . . . . 124
7.12 Actin Filaments in Lamellipodium and Lamella . . . . . . . . . . . . . 126
7.13 Actin Polymerization and Lamellipodial/Filopodial
Protrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
7.14 Actin Turnover in Lamellipodium . . . . . . . . . . . . . . . . . . . . . . . 128
7.15 Extracellular Signaling and Regulation of Actin
Polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
7.16 Actin-Based Biological Movements: Protrusion
of Lamellipodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
7.17 Other Motility Based on Actin Polymerization . . . . . . . . . . . . . . 134
7.18 Polymerization Force Developed by Lamellipodium . . . . . . . . . . 135
7.18.1 Keratocyte: Measurement with Atomic Force
Microscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
7.18.2 Fibroblasts: Measurement with Optical Trapping
Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
7.18.3 What Fluctuates? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
7.19 Reconstituted Systems to Study the Polymerization-Based
Phenomena . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
7.19.1 Actin-Liposome System . . . . . . . . . . . . . . . . . . . . . . . . 140
7.19.2 Change in Liposome Shape Accompanying Severing
of Actin Filaments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
7.19.3 Liposomes Encapsulating Tubulin . . . . . . . . . . . . . . . . . 142
7.20 Mimicking Bacteria Propulsion with Various Reconstituted
Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
7.21 Polymerization Force: Theoretical Studies . . . . . . . . . . . . . . . . . 144
7.21.1 Hill’s Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
7.21.2 Thermal Ratchet Model of Polymerization Force . . . . . . 147
7.22 The Force Measured in the Keratocyte and a Reconstituted
System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
7.23 The ATPase Activity of Actin . . . . . . . . . . . . . . . . . . . . . . . . . . 149
7.24 The Experimental Evidence of the Polymerization Force
by a Single Actin Filament . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
7.25 Generation of the Polymerization Force by Microtubule . . . . . . . 151
7.26 The Force Exerted by Depolymerization of Microtubule . . . . . . . 152
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
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Contents