chemotaxis & chemotropism

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Chemotaxis & Chemotropism Diaz Baiseitov & Bonan Liu Group 12

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Course project presentation (Warwick BS944 Advanced Biotech) 2009-2010

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Page 1: Chemotaxis & Chemotropism

Chemotaxis & Chemotropism

Diaz Baiseitov & Bonan LiuGroup 12

Page 2: Chemotaxis & Chemotropism

2

Chemotaxis

• Directed movement toward or away from specific chemicals or objectives

– Move toward nutrients, mating partner, etc.– Move away from toxins, harsh conditions, etc.

• Universal behavior in living organisms• Involves sensing and movement

It was discovered by Engelmann & Pfeffer (1883) (No further report)

Adler 1969 new discovery (Modern research began to come to notice)New theory ----------------------- Specific receptor: It induced the bacteria’s chemotaxis

Proved: The matters response to positive and negative chemotaxis are the attractant and repellents themselves not their metabolite.

Page 3: Chemotaxis & Chemotropism

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micropipette

Pipette

Neutrophil Chemotaxis

http://www.nature.com/ncb/journal/v1/n2/suppinfo/ncb0699_75_S1.html

Page 4: Chemotaxis & Chemotropism

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Two Chemotactic Strategies

Temporal Sensing (Differentiator)

tumbleelse run,straight ,0 if dt

dC

dt

dC

tt

tCtC

12

12 )()(t2

t1x1

x2

dx

dC

xx

xCxC

12

12 )()(

Spatial Sensing

22 ofdirection in shmoo ,0)(

if xdx

xdC

(reorient)

(project)

Page 5: Chemotaxis & Chemotropism

5

Examples

Temporal Sensing:Bacterial Chemotaxis

Spatial Sensing:Yeast Mating

a

A. B.

C.

Neutrophil Chemotaxis

?

Page 6: Chemotaxis & Chemotropism

Mechanism

The mechanism involves 3 components:

1. Receptors

2. Reception & Transportation of chemical signals

3. Flagella movement (Cellular motion)

Receptors:

In E.coli:

More than 20 attractant receptors more than 10 repellent receptors. (suger, protein, ion)

Site: periplasmic space or inner membrane.

Ion receptors can combine and transport divalention from outside to inside.

Page 7: Chemotaxis & Chemotropism

Mechanism

Transportation and reception of chemical signals:

Chemotaxis needs Methyl-accepting chemotaxis protein (MCP).

Two types: MCP I, MCP II

MCP methylation:(Motive force of flagella)

Demethylation

Methylation

Receptor

When the receptors feel the concentration change, it will send the message to flagella, make it clock wise or anti clock wise.

Page 8: Chemotaxis & Chemotropism

Chemotropism vs. Chemotaxis

Source: PNAS December 23, 2003 vol. 100 no. 26 16125-16130

Chemotaxis – directed movement of an organism.Chemotropism – directed growth of an organism.First observed in the pollen tubes of the plants

In A–C, 2.5 μg/μl protein was applied to wells. Pollen tubes were stained with Coomassie blue at 6-h treatment. (D) Quantification method showing positive chemotropism. (pg, pollen grain; pt, pollen tube)

Page 9: Chemotaxis & Chemotropism

Chemotropism case 1: yeast

Source: Cold Spring Harb Perspect Biol 2009;1:a001958

Yeast cells detect mating pheromones and grow towards them:

Page 10: Chemotaxis & Chemotropism

Chemotropism in yeast: the pathways

Source: Journal of Cell Science (2006) 119, 3485-3490; Nern A, Arkowitz R. JCB 1999;144:1187-1202

Polarized growth is initiated by the Cdc24 accumulated in the region of activated pheromone receptor (Gbg) with the help of adaptor protein, Far1. The MAPK pathway protein Ste5, binds to both Gbg and Bem1, whereas Bem1 binds to Far1, further linking Cdc24 and Cdc42 to this site. Activation of Ste20, an upstream member of the MAPK pathway, is dependent on Cdc42:

Page 11: Chemotaxis & Chemotropism

Chemotropism in yeast: the genes

Source: PNAS December 23, 2003 vol. 100 no. 26 16125-16130

Many complex genes are involved into chemotropic process in yeast:

Page 12: Chemotaxis & Chemotropism

Chemotropism case 2: neurons

Source: Neuroscience (2008), Fourth edition, edited by Dale Purves

Neurons (1) have innate plasticity, (2) can grow (3) but not regenerate:

Page 13: Chemotaxis & Chemotropism

Chemotropism in neurons: the growth cone

Source: Cold Spring Harb Perspect Biol 2009;1:a001958

Axonal growth cone is found to be directed by the chemotropic factors:(1) Growth cones respond to both contact mediated and chemotropic guidance cues.(2) Cues can be either attractive or repulsive.(3) Cues can act over a short or long range, and may differentially affect particular types of neurons. Only the growth cone is motile

Page 14: Chemotaxis & Chemotropism

The growth cone in its beauty

Specimen: Neuronal Growth Cone in Cell Culture; Technique: FluorescenceCredits: Dylan Burnette, Department of Molecular Cellular and Developmental Biology, Yale University

Page 15: Chemotaxis & Chemotropism

Search for neurochemotropic messengers

Source: Q.Zheng et al., The Journal of Neuroscience, February 1, 1996, 76(3):1140-l 149

Glutamate gradient driven axon growth in Xenopus spinal cord found in 1996:

Images of a growth cone at various times before and after (indicated by numbers in min) the onset of a glutamate gradient applied at time 0 from the top left comer. Lines represent the midlines of the last 20 pm of neurite.

Page 16: Chemotaxis & Chemotropism

Chemotropism in neurons: picture today

Source: Neuroscience (2008), Fourth edition, edited by Dale Purves

Page 17: Chemotaxis & Chemotropism

Chemotropism in neurons: the pathways

Source: Neuroscience (2008), Fourth edition, edited by Dale Purves

Page 18: Chemotaxis & Chemotropism

Parallel neurovascular chemotropism

Source: Brian Kinsman, Eukaryon, Vol. 5, March 2009, Lake Forest College

Recent finding: neurons and vessels probably grow in parallel driven by the same chemotropic factors

The impact of SemaIII-Nrp and Netrin-UNC5B ligand-receptor complexes on vascular growth in a blood vessel:

(1) SemaIII signaling through Nrp on endothelial cells interrupts cell-cell focal adhesion complexes to facilitate cell mobility required for vascular plasticity and outgrowth (2) Netrin signaling through UNC5B repels endothelial filopodia to inhibit new vascular growth, termed sprouting angiogenesis

Page 19: Chemotaxis & Chemotropism

Chemotropism case 3: humans?

Source: http://blog.shankbone.org/

Male armpit as one of a probable source of human pheromones:

Page 20: Chemotaxis & Chemotropism

Conclusion

Chemotaxis and Chemotropism – two basic form of motility

Common for plants, microorganisms and animal cells

Can be exploited therapeutically

Very complex and poorly understood

Yet very promising and exciting