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Page 1: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Cell to Cell Communication

Chapter 11

Page 2: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Example of Cell to Cell Communication

• Yeast’s version of sex• Two types of cells (a and )• Each secretes a mating factor that

binds to receptor on opposite cell• Binding of mating factors lead to cell

growth and fusion• Nucleus of fused cell contains DNA

from both a and .

Page 3: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.0 Yeast

Page 4: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.1 Communication between mating yeast cells

Page 5: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Local and Long Distance Signaling

• Local signaling – influences cells in the nearby vicinity– Paracrine signaling – secreting cell releases

a regulator in the the extracellular matrix– Synaptic signaling – nerve cell releases

neurotransmitter into a synapse (space between nerves)

• Long Distance signaling – can influence cells all over body– Hormone signaling – endocrine cells

secrete hormones into blood where they can reach any cell

Page 6: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.3 Local and long-distance cell communication in animals

Page 7: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.4 Communication by direct contact between cells

Cell junctions and cell-cell recognition

Page 8: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Three Stages of Cell Signaling

• Reception – target cell’s detection of a chemical signal– Signal is detected when it binds to a

receptor– Ligand – a signal molecule that binds to a

receptor• Transduction – binding of signal to receptor

stimulates a change in the receptor. – The changed receptor triggers a step or

many steps that lead to the cell response.• Response – end result – the cell response

Page 9: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.5 Overview of cell signaling (Layer 1)

Page 10: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.5 Overview of cell signaling (Layer 2)

Page 11: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.5 Overview of cell signaling (Layer 3)

Page 12: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Receptors

• Intracellular receptors – found in cytoplasm or on nucleus so signal must pass through cell membrane first

– Ex. NO and steroid hormones like testosterone

– Testosterone receptor only found in certain cells

• An activated testosterone receptor acts as a transcription factor

– Transcription factors - turn on or turn off genes

Page 13: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.10 Steroid hormone interacting with an intracellular receptor

Page 14: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

• Cell Membrane Receptors – found in cell membrane

– Three major types

• G-linked receptor

• Receptor tyrosine kinase

• Ligand-gated ion channel

Page 15: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.6 The structure of a G-protein-linked receptor

Page 16: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.7 The functioning of a G-protein-linked receptor

Page 17: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.8 The structure and function of a tyrosine-kinase receptor

Page 18: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.9 A ligand-gated ion-channel receptor

Page 19: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Transduction

• Signal transduction pathways – a chain of molecular interactions (like falling dominoes)

• Often involves protein phosphorylation and dephosphorylation– Protein kinases – enzymes that transfer

phosphate groups from ATP to a protein– Phosphorylation of protein often changes

protein from inactive to active form– Protein phosphatases – enzymes that

rapidly remove P (often turn off pathway)

Page 20: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.11 A phosphorylation cascade

Page 21: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Second Messengers

• Second messengers – small, nonprotein, water-soluble molecules or ions that are part of signaling pathways

• Two most common second messengers

– Ca2+

– Cyclic adenosine monophosphate (cAMP or cyclic AMP)

Page 22: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

cAMP

• Adenylyl cyclase – an enzyme in cell membranes that converts ATP into cAMP

• Phosphodiesterase – an enzyme that converts cAMP into AMP

Page 23: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.12 Cyclic AMP

Page 24: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11-12x cAMP

Page 25: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.13 cAMP as a second messenger

Page 26: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Ca2+

• Second messenger involved in growth factors, some hormones, muscle contractions, neurotransmitters, and cell division

• Ca2+ levels are high in the blood, ER, and sometimes mitochondria and chloroplasts

• Low Ca2+ cytosol concentration allows even small fluctuations to trigger pathways

Page 27: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.14 The maintenance of calcium ion concentrations in an animal cell

Page 28: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.15 Calcium and inositol triphosphate in signaling pathways (Layer 1)

Page 29: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.15 Calcium and inositol triphosphate in signaling pathways (Layer 2)

Page 30: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.15 Calcium and inositol triphosphate in signaling pathways (Layer 3)

Page 31: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.16 Cytoplasmic response to a signal: the stimulation of glycogen breakdown by epinephrine

Page 32: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.17 Nuclear response to a signal: the activation of a specific gene by a growth factor

Page 33: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Fine Tuning of Response

• Signal Amplification – number of activated products is much greater than in preceding step

• Specificity – different cells have different proteins so two cells can respond to same signal in different manner– Ex. epinephrine stimulates liver to break

down glycogen and heart cells to contract faster

• Scaffolding Proteins – large relay proteins to which several other relay proteins are attached

Page 34: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.18 The specificity of cell signaling

Page 35: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Figure 11.19 A scaffolding protein

Page 36: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

Apoptosis• Apoptosis - triggered by signals that

activate cell suicide

• In C. elegans (small worm), death genes called ced. When activated they stimulate death by activating proteases and nucleases.

• Very similar genes found in other animals including humans

• Apoptosis problems are associated with cancer, Parkinson’s, and alzheimer’s

Page 37: Cell to Cell Communication Chapter 11. Example of Cell to Cell Communication Yeast’s version of sex Two types of cells (a and  ) Each secretes a mating

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