Axoplasmic flow in Axons - Mechanisms and Applications in Clinical Neurology

Discussion about the historical aspects of axoplasmic flow, the mechanisms, microtubule motors, and applications in neurological diseases and therapeutics.

1. Axoplasmic transport

2. 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

3. 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

5. The Neuron
•Largest and
longest cells of
body (10
7
rbc)

6. All proteins have to come from the soma

7. “Axoplasmic flow”
•Conveyor Belt
•Passive Transport
•Gravity dependent

8. 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

9. Pioneering Work
•Concept of Axoplasmic
Flow
•Simple, elegant
experiment
•Rat Sciatic Nerve

11. Initial Response
Jordi Floch, Founder
AAN –
“Thank God! What
do you think the
nervous system is, a
plumbing system ?”

12. 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

13. 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

20. Classification of Axonal Flow
•Slow Transport
–Antegrade, 0.1 to 4 mm/day

25. Requires ATP/Mg
2+
as fuel for the motor

27. Classification of Axonal Flow
•Slow Transport
–Antegrade, 0.1 to 4 mm/day
•Fast Transport
–Antegrade at up to 400 mm/day

30. Horse Radish Peroxidase
Concentration

31. 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

32. Slow Axonal Transport

33. Slow Axonal Transport: ~1-4 mm/day
Delivery of cytosolic and cytoskeletal proteins to the nerve terminal:
Microtubules, Neurofilaments, Enzymes

34. 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

35. Fast Axonal Transport

36. The Substrate
•Microfilaments
•Microtubules
•The Package
•ATP !!!

37. Subunit: tubulin
MW: ~50 kD, a- és b-tubulin -> heterodimer
1 bound GTP or GDP;
Microtubules
a
b

38. Microtubules

39. Intermediate filaments

40. Polymerisation of IF
protofilamentum
filamentum

42. Requires ATP/Mg
2+
as fuel for the motor

43. 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

44. Kinesins

47. 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.

48. stalk
domain
N-terminal heavy
chain motor
domains (heads)


Kinesin I








hinge
light chains
C-terminal
tail domains

49. cargo
vesicle
kinesin
m
i
c
r
o
t
u
b
u
l
e

scaffolding
protein
receptor

50. Single kinesin moving a bead

51. Kinesin superfamily proteins
(KIFs) bind to cargoes through
adaptor or scaffolding protein
complexes.

52. Kinesin superfamily proteins (KIFs)
and cargoes for axonal and
dendritic transport.

53. 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

55. Walking along the microtubules
Single Headed Kinesin…

56. cargo
vesicle
kinesin
m
i
c
r
o
t
u
b
u
l
e
scaffolding
protein
receptor
inactive kinesin
Kinesin Inactivation

57. So, how does it all work together?

58. 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.

59. Dyneins

60. The dynein microtubule motor.
Biochim Biophys Acta. 2000. 1496:60-75.

61. 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

63. Summary for axoplasmic transport
•Necessity
•Types
•Kinesins
•Dyenins
•Summation
•Need for this information !!!

64. 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

66. •
•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

67. •
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

68. •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

69. •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]

70. •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.


71. •
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)

72. Is it only bad news ?

73. 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

77. 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

78. Further Reading