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Discussion about the historical aspects of axoplasmic flow, the mechanisms, microtubule motors, and applications in neurological diseases and therapeutics.
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Axoplasmic transport
Road Map for the Session
• Introduction and need for this discussion• Historical aspects and the pioneers• Characterization of the types of axoplasmic flow• The molecular “motors”• Integration of concepts• Clinical utilization of the information – pathogenesis• Clinical utilization of the information – therapeutics
• Further reading
Road Map for the Session
• Introduction and need for this discussion• Historical aspects and the pioneers• Characterization of the types of axoplasmic flow• The molecular “motors”• Integration of concepts• Clinical utilization of the information – pathogenesis• Clinical utilization of the information – therapeutics
• Further reading
The Neuron
• Largest and longest cells of body (107 rbc)
All proteins have to come from the soma
“Axoplasmic flow”
• Conveyor Belt
• Passive Transport
• Gravity dependent
Road Map for the Session
• Introduction and need for this discussion• Historical aspects and the pioneers• Characterization of the types of axoplasmic flow• The molecular “motors”• Integration of concepts• Clinical utilization of the information – pathogenesis• Clinical utilization of the information – therapeutics
• Further reading
Pioneering Work
• Concept of Axoplasmic Flow
• Simple, elegant experiment
• Rat Sciatic Nerve
Initial Response
Jordi Floch, Founder AAN –
“Thank God! What do you think the
nervous system is, a plumbing system ?”
Road Map for the Session
• Introduction and need for this discussion• Historical aspects and the pioneers• Characterization of the types of axoplasmic flow• The molecular “motors”• Integration of concepts• Clinical utilization of the information – pathogenesis• Clinical utilization of the information – therapeutics
• Further reading
Advent of electron microscopy
• Late 1960’s
• Characterization of Sub cellular structure of Neuron
• Absence of Golgi apparatus, RER and centromere from Axon
• Presence of cytoskeletal proteins, vesicles, neurofilaments and neurotubules in axon
Classification of Axonal Flow
• Slow Transport– Antegrade, 0.1 to 4 mm/day
Requires ATP/Mg2+ as fuel for the motor
Classification of Axonal Flow
• Slow Transport– Antegrade, 0.1 to 4 mm/day
• Fast Transport– Antegrade at up to 400 mm/day
Horse Radish Peroxidase Concentration
Classification of Axonal Flow
• Slow Transport– Antegrade, 0.1 to 4 mm/day
• Fast Transport– Antegrade at up to 400 mm/day– Retrograde at 40-400 mm/day
Slow Axonal Transport
Slow Axonal Transport: ~1-4 mm/day
Delivery of cytosolic and cytoskeletal proteins to the nerve terminal:
Microtubules, Neurofilaments, Enzymes
The Cytoskeletons of Neurons and Glia(and all eukaryotic cells!)
Microtubules (Tubulin)- Tubulins, MAPs, Motors: Kinesins and Dyneins
Microfilaments (Actin)-Actins, Actin Monomer Binding Proteins, Capping Proteins, Gelsolin Family, Crosslinking and Bundling Proteins, Tropomyosin, Motors: Myosin
Intermediate Filaments- Superfamily of 5 classes:Types I and II: Keratins, Type III: GFAP, Vimentin, Desmin, Peripherin, Type IV: NF Triplet,Internexin, Nestin, Type V: Nucelar Laminins
Fast Axonal Transport
The Substrate
• Microfilaments
• Microtubules
• The Package
• ATP !!!
Subunit: tubulinMW: ~50 kD, - és -tubulin -> heterodimer1 bound GTP or GDP;
Microtubules
Microtubules
Intermediate filaments
Polymerisation of IF
protofilamentum
filamentum
Requires ATP/Mg2+ as fuel for the motor
Road Map for the Session
• Introduction and need for this discussion• Historical aspects and the pioneers• Characterization of the types of axoplasmic flow• The molecular “motors”• Integration of concepts• Clinical utilization of the information – pathogenesis• Clinical utilization of the information – therapeutics
• Further reading
Kinesins
Kinesins
Kinesins are a large family of proteins with diverse structures. Mammalian cells have at least 40 different kinesin genes.
The best studied is referred to as conventional kinesin, kinesin I, or simply kinesin.
Some are referred to as kinesin-related proteins (KRPs).
Kinesin I has a structure analogous to but distinct from that of myosin.
There are 2 copies each of a heavy chain and a light chain.
stalk domain
N-terminal heavy chain motor
domains (heads)
Kinesin I
hinge light chains
C-terminal tail domains
cargo vesicle
kinesin
micro
tubule
scaffolding protein
receptor
Single kinesin moving a bead
Kinesin superfamily proteins (KIFs) bind to cargoes through adaptor or scaffolding protein complexes.
Kinesin superfamily proteins (KIFs) and cargoes for axonal and dendritic
transport.
Molecular motors: from one motor many tails to one motor many tales. Lawrence S.B. Goldstein Trends in Cell Biology, 2001, 11:12:477-482
Rafts and cytoskeletal proteins as new cargoes
Walking along the microtubules
Single Headed Kinesin…
cargo vesicle
kinesin
mic
rotu
bule
scaffolding protein
receptor
inactive kinesin
Kinesin Inactivation
So, how does it all work together?
Fast Axonal Transport: 100-400 mm/day Purpose: Transport organelles such as mitochondira and vesicles
carrying SV and plasma membrane proteins to the nerve terminal.
Also retrograde movement of vesicles containing neurotrophic factors back to the cell body.
Dyneins
The dynein microtubule motor.Biochim Biophys Acta. 2000. 1496:60-75.
Road Map for the Session
• Introduction and need for this discussion• Historical aspects and the pioneers• Characterization of the types of axoplasmic flow• The molecular “motors”• Integration of concepts• Clinical utilization of the information – pathogenesis• Clinical utilization of the information – therapeutics
• Further reading
Summary for axoplasmic transport
• Necessity• Types• Kinesins• Dyenins
• Summation
• Need for this information !!!
Road Map for the Session
• Introduction and need for this discussion• Historical aspects and the pioneers• Characterization of the types of axoplasmic flow• The molecular “motors”• Integration of concepts• Clinical utilization of the information – pathogenesis• Clinical utilization of the information – therapeutics
• Further reading
•
• Axonopathy and transport deficits early in the pathogenesis of
Alzheimer's disease. Stokin GB, Lillo C, Falzone TL, Brusch RG, Rockenstein E, Mount SL, Raman R, Davies P, Masliah E, Williams DS, Goldstein LS Science 2005 Feb 25; 307(5713):1282-8
• Selective vulnerability and pruning of phasic motoneuron axons in motoneuron disease alleviated by CNTF.Pun S, Santos AF, Saxena S, Xu L, Caroni PNat Neurosci
2006 Mar 9(3):408-19
• Charcot-Marie-Tooth disease type 2A caused by mutation in a
microtubule motor KIF1Bbeta.Zhao C, Takita J, Tanaka Y, Setou M, Nakagawa T, Takeda S, Yang HW, Terada S, Nakata T, Takei Y, Saito M, Tsuji S, Hayashi Y, Hirokawa NCell 2001 Jun 1 105(5):587-97
• 1-Methyl-4-phenylpyridinium induces synaptic dysfunction through a pathway involving caspase and PKCdelta enzymatic activities. Proc Natl Acad Sci U S A. 2007 Feb
13;104(7):2437-41 – Model for neurodegenration
• Jones LG, Prins J, Park S, Walton JP, Luebke AE, Lurie DI.
• Lead exposure during development results in increased neurofilament phosphorylation, neuritic beading, and temporal processing deficits within the murine auditory brainstem.
• J Comp Neurol. 2008 Feb 20;506(6):1003-17.
• Pan T, Kondo S, Le W, Jankovic J.
•The role of autophagy-lysosome pathway in neurodegeneration associated with Parkinson's disease.
• Brain. 2008 Jan 10; [Epub ahead of print]
• Inflammation, demyelization,neurodegeneration, and neuroprotection in the pathogenesis of
mutliple sclerosis. Peterson, Lisa K., Fujinami, Robert S.
• Journal Neuroimmunology 184 (2007): 37-44
•Sodium channels and multiple sclerosis: Role in symptom production,
damage and therapy. Smith, Kenneth J.
• Brain Pathology 2007 Apr;17(2):230-42.
•Proteomic analysis of rat cortical neurons after fluoxetine (FLUX) treatment
• Long-Term Impairment of Anterograde Axonal Transport Along Fiber Projections Originating in the Rostral Raphe Nuclei After Treatment With Fenfluramine or Methylenedioxymethamphetamine (MDMA)
Is it only bad news ?
Road Map for the Session
• Introduction and need for this discussion• Historical aspects and the pioneers• Characterization of the types of axoplasmic flow• The molecular “motors”• Integration of concepts• Clinical utilization of the information – pathogenesis• Clinical utilization of the information – therapeutics
• Further reading
Road Map for the Session
• Introduction and need for this discussion• Historical aspects and the pioneers• Characterization of the types of axoplasmic flow• The molecular “motors”• Integration of concepts• Clinical utilization of the information – pathogenesis• Clinical utilization of the information – therapeutics
• Further reading
Further Reading