| Introduction / Chapter 1： |
| Channels and ions are needed for excitation |
| Channels get names |
| Channels have families |
| Ohm's law is central |
| The membrane as a capacitor |
| Equilibrium potentials and the Nernst equation |
| Current-voltage relations of channels |
| Ion selectivity |
| Signaling requires only small ion fluxes |
| Description of Channels / Part I： |
| Classical Biophysics of the Squid Giant Axon / Chapter 2： |
| The action potential is a regenerative wave of Na[superscript +] permeability increase |
| The voltage clamp measures current directly |
| The ionic current of axons has two major components: I[subscript Na] and I[subscript K] |
| Ionic conductances describe the permeability changes |
| Two kinetic processes control g[subscript Na] |
| The Hodgkin-Huxley model describes permeability changes |
| The Hodgkin-Huxley model predicts action potentials |
| Do models have mechanistic implications? |
| Voltage-dependent gates have gating charge and gating current |
| The classical discoveries recapitulated |
| The Superfamily of Voltage-Gated Channels / Chapter 3： |
| Drugs and toxins help separate currents and identify channels |
| Drugs and toxins act at receptors |
| Gates open wide at the cytoplasmic end of the pore, and the pore narrows at the outside |
| Early evidence for a pore came from biophysics |
| There is a diversity of K channels |
| Voltage-gated Na channels are less diverse |
| Ion channels can be highly localized |
| Voltage-gated channels form a gene superfamily |
| The crystal structure shows a pore! |
| Patch clamp reveals stochastic opening of single ion channels |
| Recapitulation |
| Voltage-Gated Calcium Channels / Chapter 4： |
| Early work found Ca channels in every excitable cell |
| Ca[superscript 2+] ions can regulate contraction, secretion, and gating |
| Ca[superscript 2+] dependence imparts voltage dependence |
| Multiple channel types: Dihydropyridine-sensitive channels |
| Neurons have many HVA Ca-channel subtypes |
| Voltage-gated Ca channels form a homologous gene family |
| A note on Ca-channel nomenclature |
| Permeation and ionic block require binding in the pore |
| Do all Ca channels inactivate? |
| Channel opening is voltage-dependent and delayed |
| Overview of voltage-gated Ca channels |
| Potassium Channels and Chloride Channels / Chapter 5： |
| Fast delayed rectifiers keep short action potentials short |
| Slow delayed rectifiers serve other roles |
| Transient outward currents space repetitive responses |
| Shaker opens the way for cloning and mutagenesis of K channels |
| Ca[superscript 2+]-dependent K currents make long hyperpolarizing pauses |
| Spontaneously active cells can serve as pacemakers |
| Inward rectifiers permit long depolarizing responses |
| What are K[subscript ir] channels used for? |
| The 4TM and 8TM K channels |
| The bacterial KcsA channel is much like eukaryotic K channels |
| An overview of K channels |
| A hyperpolarization-activated cation current contributes to pacemaking |
| Several strategies underlie slow rhythmicity |
| Cl channels stabilize the membrane potential |
| Cl channels have multiple functions |
| Ligand-Gated Channels of Fast Chemical Synapses / Chapter 6： |
| Ligand-gated receptors have several architectures |
| Acetylcholine communicates the message at the neuromuscular junction |
| Agonists can be applied to receptors in several ways |
| The decay of the endplate current reflects channel gating kinetics |
| Fluctuation analysis supported the Magleby-Stevens hypothesis |
| The ACh receptor binds more than one ACh molecule |
| Gaps in openings reveal slow agonist unbinding |
| Agonist usually remains bound while the channel is open |
| Ligand-gated receptors desensitize |
| An allosteric kinetic model |
| Recapitulation of nAChR channel gating |
| The nicotinic ACh receptor is a cation-permeable channel with little selectivity |
| Fast chemical synapses are diverse |
| Fast inhibitory synapses use anion-permeable channels |
| Excitatory amino acids open cation channels |
| Recapitulation of fast chemical synaptic channels |
| Modulation, Slow Synaptic Action, and Second Messengers / Chapter 7： |
| cAMP is the classic second messenger |
| cAMP-dependent phosphorylation augments I[subscript Ca] in the heart |
| Rundown could be related to phosphorylation |
| cAMP acts directly on some channels |
| There are many G-protein-coupled second-messenger pathways |
| ACh reveals a shortcut pathway |
| Synaptic action is modulated |
| G-protein-coupled receptors always have pleiotropic effects |
| Encoding is modulated |
| Pacemaking is modulated |
| Slow versus fast synaptic action |
| Second messengers are launched by other types of receptors |
| First overview on second messengers and modulation |
| Sensory Transduction and Excitable Cells / Chapter 8： |
| Sensory receptors make an electrical signal |
| Mechanotransduction is quick and direct |
| Visual transduction is slow |
| Vertebrate phototransduction uses cyclic GMP |
| Phototransduction in flies uses a different signaling pathway |
| Channels are complexed with other proteins |
| Chemical senses use all imaginable mechanisms |
| Pain sensation uses transduction channels |
| What is an excitable cell? |
| Calcium Dynamics, Epithelial Transport, and Intercellular Coupling / Chapter 9： |
| Intracellular organelles have ion channels |
| IP[subscript 3]-receptor channels respond to hormones |
| Ca-release channels can be studied in lipid bilayers |
| The ryanodine receptor of skeletal muscle has recruited a voltage sensor |
| Voltage-gated Ca channels are the voltage sensor for ryanodine receptors |
| IP[subscript 3] is not the only Ca[superscript 2+]-mobilizing messenger |
| Intracellular stores can gate plasma-membrane Ca channels |
| The extended TRP family is diverse |
| Mitochondria clear Ca2+ from the cytoplasm by a channel |
| Protons have channels |
| Transport epithelia are vectorially constructed |
| Water moves through channels as well |
| Cells are coupled by gap junctions |
| All cells have other specialized intracellular channels |
| Recapitulation of factors controlling gating |
| Principles and Mechanisms of Function / Part II： |
| Elementary Properties of Ions in Solution / Chapter 10： |
| Early electrochemistry |
| Aqueous diffusion is just thermal agitation |
| The Nernst-Planck equation describes electrodiffusion |
| Uses of the Nernst-Planck equation |
| Brownian dynamics describes electrodiffusion as stochastic motions of particles |
| Electrodiffusion can also be described as hopping over barriers |
| Ions interact with water |
| The crystal radius is given by Pauling |
| Ion hydration energies are large |
| The "hydration shell" is dynamic |
| "Hydrated radius" is a fuzzy concept |
| Activity coefficients reflect weak interactions of ions in solution |
| Equilibrium ion selectivity can arise from electrostatic interactions |
| Recapitulation of independence |
| Elementary Properties of Pores / Chapter 11： |
| Early pore theory |
| Ohm's law sets limits on the channel conductance |
| The diffusion equation also sets limits on the maximum current |
| Summary of limits from macroscopic laws |
| Dehydration rates can reduce mobility in narrow pores |
| Single-file water movements can lower mobility |
| Ion fluxes may saturate |
| Long pores may have ion flux coupling |
| Ions must overcome electrostatic barriers |
| Ions could have to overcome mechanical barriers |
| Gramicidin A is the best-studied model pore |
| Electrostatic barriers are lowered in K channels |
| A high turnover number is good evidence for a pore |
| Some carriers have pore-like properties |
| Recapitulation of pore theory |
| Counting Channels and Measuring Fluctuations / Chapter 12： |
| Neurotoxins count toxin receptors |
| Gating current counts mobile charges within the membrane |
| Digression on the amplitudes of current fluctuations |
| Fluctuation amplitudes measure the number and size of elementary units |
| A digression on microscopic kinetics |
| The patch clamp measures single-channel currents directly |
| Summary of single-channel conductance measurements |
| Thoughts on the conductance of channels |
| Channels are not crowded |
| Structure of Channel Proteins / Chapter 13： |
| The nicotinic ACh receptor is a pentameric glycoprotein |
| Complete amino acid sequences were determined by cloning |
| Ligand-gated receptors form a large homologous family |
| Determining topology requires chemistry |
| Electron microscopy shows a tall hourglass |
| A partial crystal structure shows a pentameric ring |
| Voltage-gated channels also became a gene superfamily |
| Are K channels tetramers? |
| Auxiliary subunits change channel function |
| KcsA is a teepee |
| Electron paramagnetic resonance probes structure |
| Kv channels have a lot of mass hanging as a layer cake in the cytoplasm |
| Excitatory GluRs combine parts of two bacterial proteins |
| Is there a pattern? |
| Selective Permeability: Independence / Chapter 14： |
| Partitioning into the membrane can control permeation |
| The Goldman-Hodgkin-Katz equations describe a partitioning-electrodiffusion model |
| Uses of the Goldman-Hodgkin-Katz equations |
| Derivation of the Goldman-Hodgkin-Katz equations |
| A more generally applicable voltage equation |
| Voltage-gated channels have high ion selectivity |
| Other channels have low ion selectivity |
| Ion channels act as molecular sieves |
| Selectivity filters can be dynamic |
| First recapitulation of selective permeability |
| Selective Permeability: Saturation and Binding / Chapter 15： |
| Ionic currents do not obey the predictions of independence |
| Simple models for one-ion channels |
| Na channel permeation can be described by state models |
| Some channels must hold more than one ion at a time |
| Single-file multi-ion models |
| Multi-ion pores can select by binding |
| Anion channels have complex transport properties |
| Recapitulation of selective permeation |
| What do permeation models mean? |
| Classical Mechanisms of Block / Chapter 16： |
| Affinity and time scale of the drug-receptor reaction |
| Binding in the pore can make voltage-dependent block: Protons |
| Some blocking ions must wait for gates to open: Internal TEA |
| Local anesthetics give use-dependent block |
| Local anesthetics alter gating kinetics |
| Antiarrhythmic action |
| State-dependent block of ligand-gated receptors |
| Multi-ion channels may show multi-ion block |
| STX and TTX are the most potent and selective blockers of Na channels |
| Some scorpion toxins plug K channel pores |
| Recapitulation of blocking mechanisms |
| Structure-Function Studies of Permeation and Block / Chapter 17： |
| Charges in the M2 segment help nAChR channels conduct |
| What can a charged residue do? |
| Channel blockers interact with M2 and M1 segments |
| Cysteine substitution can test accessibility of residues |
| The S5-S6 linker forms the outer funnel and pore in K channels |
| The S5-S6 linker forms the outer funnel and pore in Na channels |
| Divalent/monovalent selectivity depends on charge density and electrostatics |
| The S6/M2 segment contributes to the inner pore |
| Inward rectification is voltage-dependent block |
| Functions are not independent |
| Recapitulation of structure-function studies |
| Gating Mechanisms: Kinetic Thinking / Chapter 18： |
| First recapitulation of gating |
| Proteins change conformation during activity |
| Events in proteins occur across the frequency spectrum |
| Topics in classical kinetics |
| Additional kinetic measures are essential |
| Most gating charge moves in significant steps |
| A new round of kinetic models for Shaker K channel gating |
| For BK channels we need three-dimensional kinetic models |
| Na[subscript v] and Ca[subscript v] channels require more complex models |
| Channels can have several open states |
| Conclusion of channel gating kinetics |
| Gating: Voltage Sensing and Inactivation / Chapter 19： |
| Simple equilibrium principles of voltage sensing and charge movement |
| Early mutagenesis points to the S4 segment |
| The S4 segment does carry much of the gating charge |
| Several residues in S4 move fully across the membrane |
| Movements around S4 are observed optically |
| Recapitulation of voltage sensing |
| What is a gate? |
| Pronase clips inactivation gates |
| Inactivation is coupled to activation |
| Microscopic inactivation can be rapid and voltage-independent |
| Fast inactivation gates are tethered plugs |
| Fast inactivation of Na channels involves a cytoplasmic loop |
| Slow inactivation is distinct from fast inactivation: A new gate? |
| Recapitulation of inactivation gating |
| Modification of Gating in Voltage-Sensitive Channels / Chapter 20： |
| Many peptide toxins slow inactivation |
| A group of lipid-soluble toxins changes many properties of Na channels |
| Reactive reagents eliminate inactivation of Na channels |
| External Ca[superscript 2+] ions shift voltage-dependent gating |
| Surface-potential calculations |
| Much of the negative charge is on the channel |
| Surface-potential theory has shortcomings |
| Recapitulation of gating modifiers |
| What are models for? |
| Cell Biology and Channels / Chapter 21： |
| Channel genes can be identified by classical genetics |
| Expression of channels is dynamic during development |
| Transcription of nAChR genes is regulated by activity, position, and cell type |
| Channel mRNA can be alternatively spliced and edited |
| Channel synthesis and assembly occurs on membranes |
| Sequences on channel subunits are used for quality control |
| Membrane proteins can be localized and immobilized |
| nACh receptors become clustered and immobilized |
| Multivalent PDZ proteins cluster channels at glutamatergic synapses |
| Channels are sorted and move in vesicles |
| Evolution and Origins / Chapter 22： |
| Channels of lower animals resemble those of higher animals |
| Channels are prevalent in eukaryotes and prokaryotes |
| Channels mediate sensory-motor responses |
| Channel evolution is slow |
| Gene duplication and divergence create families of genes |
| Proteins are mosaics |
| Speculations on channel evolution |
| Conclusion |
| References |
| Index |
図書
