E. Basic Molecular Biology - Interaction between cells Flashcards

1
Q

Cell Adhesion:
2 main categories =

A
  • cell to cell
  • Cell to extracellular matrix
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2
Q

4 main types of permanent cell junctions:

A

adherens junctions
Desmosomes
Tight junctions
Gap junctions

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3
Q

Similarities in cell-cell adhesion in adherens junctions and desmosomes:

A
  • intracellular cytoskeletal filaments of adjacent cells are joined by means of special membrane
    structures
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4
Q

Similarities in cell-cell adhesion in adherens junctions and desmosomes:

A
  • intracellular cytoskeletal filaments of adjacent cells are joined by means of special membrane
    structures
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5
Q

What do actin filaments do?

A
  • determine shape of cell surface and responsible for locomotion
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6
Q

What is the role of intermediate firmaments eg. Keratin? (2)

A
  • provide mechanical strength
  • Bundles of fibres join the cell membranes
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7
Q

Actin and intermediate filaments need to join to equivalent fibres in adjacent cells:

  • adherens junctions bind actin of adjacent cells to coordinate ______ and activity
  • Desmosomes bind _________ filaments of adjacent cells to provide mechanical strength
A

motility
intermediate

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8
Q

Cell-to-cell adhesion junctions:

A
  • both types of junctions (adherens and desmosomes) use the same family of transmembrane adhesion proteins: cadherins
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9
Q

What are cadherins? (6)

A
  • many members
  • Highly tissue specific
  • Attachment is stabilised by Ca2+
  • Cadherin - transmembrane protein meeting with hook arrangement in the middle
  • Single adherens junction of desmosomes is made of a cluster of numerous cadherin pairs
  • Attach indirectly to cytoskeleton > anchor proteins bind cadherin to intracellular filament (include B catenin)
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10
Q

General scheme to adherens junctions and desmosomes: (2)

A
  • transmembrane cadherins bind by means of extracellular domain to identical
    cadherins on neighbouring cell
  • Intracellular domain binds by means of specific anchor proteins to the
    cytoskeleton
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11
Q

What is B catenin? (4)

A
  • transcription factor in WNT pathway
  • If it is taken up by formation of adherens junctions then it is unable to function
    as a transcription factor, reduction in WNT pathway activation
  • Contributes to contact inhibition > when cells meet, Join and form adherens junctions they stop
    dividing. Important feature esp in epithelia
  • Pemphigus > antibodies to cadherins of skin, skin cells do not adhere properly thus form blisters and peel off
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12
Q

Mechanism used for cell-matrix adhesion: (2)

A
  • proteins used are integrins
  • Bind actin and intermediate filaments (esp keratin)
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13
Q

What are Integrins? (4)

A
  • alpha and beta subunit combine to form binding site for extracellular protein
  • Beta subunit anchors to filaments inside cell (not direct > connects to anchor protein)
  • Bind specific sequences in ECM molecules (RGD) by means of binding site
    from both chains
  • Family - 18 alpha and 8 beta chains > can combine in diff ways to change properties and functions
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14
Q

Integrins always recognise the same sequence of aa (RGD)

Binding cytoskeleton to basement membrane (extracellular matrix) > ________

_______ > antibody components of hemidesmosome

A

hemidesmosome
Pemphigoid

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15
Q

Integrins always recognise the same sequence of aa (RGD)

Binding cytoskeleton to basement membrane (extracellular matrix) > ________

_______ > antibody components of hemidesmosome

A

hemidesmosome
Pemphigoid

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16
Q

Effect of binding to ECM on intracytoplasmic portion of integrin: (2)

A
  • activate from inside or outside
  • Outside in > binding of something on the outside initiating the inside of the integrin
17
Q

Effect of binding to ECM on intracytoplasmic portion of integrin —->

  • Effects of outside - in activation: (5)
A
  • Binding of ligands to extracellular domain leads to changes in intracellular domains, can activate a number of pathways (eg. MAPK)
  • Cells often require co-stimulation of integrin activation for full activation of other pathways
  • Activation recruits kinases which phosphorylates nearby proteins creating docking sites for many signalling proteins
  • No docking = no signalling
  • Consequences of facilitation of signalling > most cells need to be attached to the ECM to survive and proliferate > anchorage dependence for cell survival
18
Q
  • Inside out ___ change inside (anchor binding) and leads to activation of outside
19
Q

Transient adhesion and cell migration: (2)

A
  • adhesion that can be formed and broken down (allowing cells to crawl
    through ECM)
  • Undergoes inside out deactivation
20
Q

Cell-to-cell adhesion using integrins: (5)

A
  • mediated by adhesion of an integrin to a member of the immunoglobulin superfamily/ICAM group of proteins
  • Transient association
  • Does not connect the cytoskeleton
    (only cell surface)
  • Eg. Neutrophils and endothelium
  • Inside out activation of integrin
21
Q

Tissue dynamics
Growth and turnover of tissues require: (4)

A
  • proliferation
  • Differentiation
  • Maturation
  • Cell death
    ● precisely controlled in terms of space and time
22
Q

How proliferation is controlled:
Drivers of proliferation and ______ inhibitors

23
Q

How proliferation is controlled:
Drivers of proliferation and ______ inhibitors

24
Q

What is differentiation? (3)

A
  • process of becoming different from parent cell in order to develop a more distinct form and function within a tissue
  • Embryo gives rise to differentiated cells such as muscle, skin and neurons during development form single undifferentiated cell
  • Terms associated with this include “lineage”, “commitment” and “hierarchy”
25
What is Maturation? (2)
- process of becoming a fully functional cell - Occurs once there is complete commitment to a specific lineage
26
What is Haemopoiesis?
- haemopoietic system as an illustration of differentiation and maturation
27
Cell fate depends on the receptor it expresses and the growth factors it encounters Growth factors: (4)
- lineage specific with some redundancy - Required for survival at all stages of differentiation and maturation - Required for proliferation - Eg. IL3, erythropoietin, thrombopoietin, GM-CSF, G-CSF
28
Cell fate depends on the receptor it expresses and the growth factors it encounters Maturation: (3)
- occurs after commitment - First recognisable cell = blast - Cross over in proliferation and maturation
29
Capacity to proliferate Transit amplification cells > able to proliferate actively Mature cells > usually __ ____ proliferate
do not
30
What is the intestinal villus? (3)
- regenerated every 3 to 5 days - with cells of 4 lineages (enterocytes, goblet, enteroendocrine and Paneth cells) - All come from same stem cell - When TA cells reach the top of the crypt they stop proliferating, then differentiate and position themselves
31
What is the Muscle satellite cell? (4)
- allows to replace and repair muscle fibres - Activation by, 1. NO (nitric oxide), 2. Growth factors, 3. ECM - Nitric oxide release is signal to initiate division (release ends suddenly) - Starts to divide to replace damaged cell
32
Defining characteristics of stem cells: (2)
- Self renewal - unlimited or prolonged ability to produce a daughter cell which is identical to the parent - At least one type of highly differentiated descendant
33
What are the types of stem cells? (2)
- embryonic - Adult > in all tissues and specific for each type, more differentiated than embryonic stem cell
34
How are stem cells maintained? (3)
- prevention of differentiation and inappropriate proliferation - Factors intrinsic to the stem cell (eg activation of certain TFs and pathways) - The stem cell niche (the microenvironment)
35
- The stem cell niche (the microenvironment) : (4)
- Ext signals controlling stem cell fate - Cell-cell interactions mediated by integral membrane proteins - Integrins and ECM. Integrins hold cells within a niche. ECM can modulate conc of growth factors - Secreted factors (Wnt ligands, TGFB)
36
How does the stem cell produce daughter cells with differing fates? (3)
- asymmetric cell division - One daughter cell is excluded from the niche > comes under influence of a diff microenvironment - One daughter cell receives more of a fate-inducing factor