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Cells to Organisms - Lectures > Lecture 8. Cell to Cell Communication > Flashcards

Lecture 8. Cell to Cell Communication Flashcards

1
Q

What are the two categories of cell signaling ?

A
  1. Contact dependent/Juxtacrine signaling

2. Secreted molecules

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2
Q

What are the types of juxtacrine signaling ?

A
  1. Gap junctions
  2. Plasmodesmata
  3. Notch
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3
Q

What are the types of secreted molecule signaling ?

A
  1. Autocrine signaling
  2. Paracrine signaling
  3. Endocrine signaling
  4. Paracrine signaling synaptic
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4
Q

What is juxtacrine signaling ?

A

The direct connection of adjacent cells by tiny channels that allow the movement of intracellular signaling molecules between cells

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5
Q

What do gap junctions provide ?

A

Cytoplasmic channels from one cell to an adjacent cell

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6
Q

What do gap junctions consist of ?

A

Membrane proteins called transmembrane connexins extending from the membrane of two cells

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7
Q

In gap junctions, what do the transmembrane connexins create ?

A

Pores

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8
Q

What are gap junctions necessary for ?

A

Communication between cells in many tissues such as heart muscle and in animal embryo

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9
Q

What are cardiomyocytes ?

A

Heart muscles which contract to make the heart beat

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10
Q

What is the lifecycle of a cardiomyocyte ?

A

They pump blood around the body from the moment of development of the heart in the womb until the moment of death

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11
Q

What is a characteristic of cardiomyocytes ?

A

They are autorhythmic

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12
Q

What is meant by autorhythmic ?

A

They generate their own action potential and rather than having a resting membrane potential they have a constantly cycling, changing membrane potential

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13
Q

What are the connections between cardiomyocytes called ?

A

Intercalated discs

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14
Q

What do intercalated discs contain ?

A

Anchoring proteins called desmosomes and the gap junctions

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15
Q

What do gap junctions form in cardiomyocytes ?

A

Channels between adjacent cardiac muscle fibres that allow the depolarising current produced by cations to flow from one cardiac muscle to the next

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16
Q

What are the gap junctions connecting the cardiomyocytes known as ?

A

Electrical coupling

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17
Q

What does electrical coupling in cardiac muscles allow ?

A

The quick transmission of action potentials and the coordinated contraction of the entire heart

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18
Q

What is the functional unit of contraction ?

A

Functional syncytium

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19
Q

What are plasmodesmata ?

A

Gaps that connect plant cells

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20
Q

What is inside the plasmodesmata ?

A
  1. A tubule of endoplasmic reticulum

2. Cytoplasmic sleece

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21
Q

What are the two ways that molecules can move through the plasmodesmata ?

A
  1. Proteins can move through the endoplasmic reticulum

2. Most things pass through the cytoplasmic sleeve

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22
Q

Why can most molecules pass through the cytoplasmic sleeve in the plasmodesmata ?

A

The cytoplasm is effectively continuous in between one cell and the next

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23
Q

Why is the effectively continuous cytoplasm important in plants ?

A

Allows metabolites, protein and nucleic acid to move between cells rapidly

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24
Q

What is the negative side of the continuous cytoplasmic sleeve ?

A

Viruses can spread rapidly through the plant

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25
Q

Why is notch signaling important ?

A

It is important in a number in developmental decisions, learning, memory and glial support of neurons

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26
Q

What is notch ?

A

A receptor molecule

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27
Q

Where is notch expressed ?

A

On the cell surface

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28
Q

What does notch interact with ?

A

Ligands on the cell surface

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29
Q

What are the ligands that notch interacts with in humans called ?

A
  1. Delta

2. Jagged

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30
Q

What are delta and jagged ?

A

Transmembrane proteins which have extracellular portions largely made up of EGF domains that allow interactions

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31
Q

What happens when delta binds to notch ?

A

An extracellular protease called ADAM10 carries out an S2 cleavage of notch by removing the extracellular domain to form an S3 protein

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32
Q

How is a notch intracellular domain formed from aa S3 protein ?

A

Gamma secretase within the membrane cleaves the membrane traversing part of the S3 protein

33
Q

Where does the notch intracellular domain translocate to ?

A

The nucleus

34
Q

What happens when the notch intracellular domain in the nucleus ?

A

It binds and removes the co-repressor allowing the transcription of target genes

35
Q

What is autocrine signaling ?

A

When signaling molecules are released and then act on the cell that produces them

36
Q

What are antigen presenting cells ?

A

Usually dendritic cells, which are phagocytic and can produce very small protein sequences called epitopes

37
Q

What are epitopes ?

A

Very small protein sequences produces by antigen presenting cells

38
Q

Where are epitopes presented on ?

A

The outside of the cell by a complex of proteins called a major histo-compatability complex

39
Q

What does the MHC class II complex produce ?

A

A small amount of bacterial protein which is recognised by naiive T-cells using their receptor

40
Q

What does the T-cell trigger the release of ?

A

Interleukin-2

41
Q

What is interleukin-2 important for ?

A

The replication of T-cells so that the antigen can be recognised all over the body

42
Q

How does the interleukin-2 act ?

A

On T-cells themselves by binding the proliferation of the T-cell clone - autocrine

43
Q

What is paracrine signaling ?

A

Signaling molecules are released and act locally on nearby cells

44
Q

What are some examples of paracrine signaling ?

A
  1. Cytokines released by immune cells act on multiple populations
  2. Morphogens released to drive patterning during development
  3. Neurotransmitters released locally act on multiple targets
45
Q

What are morphogens ?

A

Signaling molecules that emanate from a restricted region of tissue and spread away from their source to form a gradient

46
Q

How do Wnt proteins act ?

A

Wnt proteins act as morphogens in a concentration dependent manner through the formation of gradients within tissues

47
Q

Where are WNTs produced ?

A

In the endoplasmic reticulum

48
Q

What do WNTs undergo post translational modifications by ?

A

Palmitoleic and palmitic acid

49
Q

Where do WNTs undergo post translational modifications ?

A

Conserved cysteine residues using the enzyme acyltransferase porcupine in the endoplasmic reticulum

50
Q

What happens to WNTs at the endoplasmic reticulum ?

A

Vesicles bud off

51
Q

What is feature of the golgi allows the vesicles to bind to the membrane with the aid of a chaperone protein ?

A

Its hydrophobic

52
Q

What is the chaperone protein that aids vesicles to bind to the membrane ?

A

WNTless

53
Q

Where does WNT signaling pathway occur at ?

A

Receptor cells

54
Q

What is WNT protein’s receptor called ?

A

Frizzled

55
Q

What does frizzled stimulate ?

A

The canonical pathway

56
Q

What happens in the canonical pathway ?

A

A protein called beta catenin is stabilised in the cytoplasm

57
Q

What happens to beta catenin when WNT signaling is not occuring ?

A

It gets degraded in the cytoplasm and cant carry out signaling function

58
Q

What happens when there is a high concentration of beta catenin accumulating in the cytoplasm ?

A

It is able to be transported to the nucleus and can bind to the transcription factor TCF, which turns on new gene expression

59
Q

What is an example of paracrine signaling ?

A

Neurotransmission

60
Q

What is the neuromuscular junction ?

A

The place where neurons synapse directly onto a muscle

61
Q

Where are neurotransmitters contained ?

A

Inside neurotransmitter vesicles

62
Q

When does endocrine signaling occur ?

A

When a secretory cell secretes a signaling molecule/hormone into the blood stream for action at distal sites

63
Q

Where is insulin released from ?

A

Pancreas

64
Q

What is an example of endocrine signaling ?

A

Insulin

65
Q

What does insulin promote ?

A

The uptake of glucose from the blood into organs

66
Q

What is glucose stored in blood as ?

A

An energy containing molecule

67
Q

What is transcribed to make insulin messenger RNA

A

Insulin gene

68
Q

Where is insulin messenger RNA translated in ?

A

The endoplasmic reticulum

69
Q

What is the insulin messenger RNA translated as ?

A

A preproinsulin

70
Q

What is a preproinsulin ?

A

A much longer protein which is partially degraded to produce a mature molecules which is folded and released

71
Q

Where is the preproinsulin transported to ?

A

The golgi

72
Q

What happens to the preproinsulin in the golgi ?

A

Post translational modifications in the trans golgi network before being packaged into vesicles

73
Q

What is the function of the secretory granules containing mature insulin >

A

Can travel within the cell and further signaling events occur to hone it to membrane

74
Q

What is glucose sensed by ?

A

Glucose transporter on the cell surface

75
Q

What happens when glucose is high ?

A

Insulin is stimulated to be released

76
Q

Where is the glucose then transported to when glucose is high ?

A

Transported to the cytoplasm of the beta cells in the pancreas by glucose transporter

77
Q

What can happen as a result of glucose being an energy substrate ?

A

It can be rapidly glycolysed and then pyruvate from the glycolysis is further metabolised in the TCA cycle in mitochondria, increasing ATP

78
Q

What happens as a result of the elevated ATP levels ?

A

Drives the potassium channel, which changes the voltage in the cell and can open the calcium channels allowing calcium to flow and cause the cell to undergo calcium dependent exocytosis

79
Q

What is paracrine signaling synaptic ?

A

When the signaling cell transmits information in the form of changes in membrane potential along the length of the cell

Cells to Organisms - Lectures (36 decks)

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