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Module Assessment 2: Cell Signaling > Module Assessment 2: Cell Signaling > Flashcards

Module Assessment 2: Cell Signaling Flashcards

1
Q

morphogenesis

A

the construction of organized from in the developing organism. Relies on cell-cell signaling

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2
Q

determined cell

A

When a specific set of pathways is turned on, the cell takes on a specific identity. Cells can become determined by external signaling.

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3
Q

Cell-Cell Communication is between…

A

cells that are next to each other
cell that are near eachother
cells that are far away from each other
-> cell signaling can occur at close proximity, or farther away

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4
Q

endocrine signaling

A

cells release factors into the blood stream that later reach other areas of the body

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5
Q

paracrine signaling

A

cell signaling between cells in close proximity to one another

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6
Q

autocrine signaling

A

cell signals and then responds to its own signals

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7
Q

juxtacrine signaling

A

cell signaling between that are directly next to one another. signal is physically connected to the cell that sends the signal

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8
Q

Differential Cell Affinity (Steps)

A

Towns and Holtfretter (1955)
1. epidermal and neural plate cells are extracted from a Xenopus embryo.
2. cells are mixed to form an aggregate
3. Over time, cells separate by cell type.

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9
Q

Differential Cell Affinity (Key Takeaways)

A
  1. Reaggregated cells become spatially segregated
  2. Final positions reflect embryonic positions
  3. Selective affinities can be changed over the course of development
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10
Q

Differential Cell Adhesion Hypothesis

A

Steinberg (1964)
cells rearrange themselves into the most thermodynamically favorable pattern. Cells associate with one another in a hierarchy.

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11
Q

What dictates where boundaries are created?

A
  1. The number type of adhesion molecules: some adhesion molecules make stronger bonds than others
  2. the number of adhesion molecules: increasing the number of molecules allows cells to make stronger bonds with their neighbors
    these properties dictate surface tension, and how quickly these cells come together- cells that come together quicker organize closer to the center of the embryo
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12
Q

cadherins

A

-calcium-dependent adhesion molecules: removing calcium causes cadherins to lose structural integrity, causing the tissue to fall apart. These connections are restored when calcium is returned
-form homotypic complexes: only bind like cadherins
-phosphorylation changes characteristics
-transmembrane proteins
-forms a protein-protein interface

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13
Q

E-Cadherins

A

in the epithelial

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14
Q

P-Cadherins

A

placental

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15
Q

N-Cadherins

A

Neural

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16
Q

EP-Cadherins

A

between the blastomeres during gastrulation

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17
Q

Protocadherins

A

lack catenin binding regions

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18
Q

integrins

A

-transmembrane protein binding from the ECM to the inside of the cell at the cytoskeleton
-creates heterotypic dimers
bind to laminin, fibronectin, collagen etc. Allows cells to move along and connect to different types of the ECM

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19
Q

What is the use of cadherins

A

cadherins are essential for early development as well as organization of the early embryo. Antagonizing cadherins causes disorganization and improper tissue formation

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20
Q

What is the use of integrins

A

Integrins play a major role in signaling. Signaling affects both gene expression and cytoskeletal organization. this is important for tissue development and morphogenesis
-reciprocal connection between the ECM and csk
-biochemical connection to the cell cortex. Activation of ras signaling induces many pathways

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21
Q

mesenchymal cells

A

cells that can freely move throughout the developing embryo

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22
Q

epithelial cells

A

cells bound to one another and the basal membrane. These cells are stationary and cannot move freely

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23
Q

EMT Transition

A
  1. Cell receives signals from paracrine factors, signaling change in cell phenotype
  2. Catenines are degraded
  3. cadherins are endocytosed into the cell
  4. cell secretes proteases that break down the basal lamina
  5. cell produces new integrins, allowing it to move about the ECM
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24
Q

Where does the EMT transition most commonly occur

A

Neural crest cells, epiblast of the embryo

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25
inducer
cell releasing the signal
26
competent cell
must have the correct receptors as well as the ability to respond to the signal. example: optic vesicle only induces lens formation in the correct tissue. This tissue as the correct receptors to respond to the signal.
27
ligands
small signaling molecules that bind to receptors
28
diffusible ligands
small to large molecules including Growth Factors. Also includes factors diffusing from the ECM
29
non-diffusible ligands
molecules embedded in the membrane of the transmitting cell or ECM factors
30
ion channel linked receptors
effect ion transport, often ligand gated
31
G-protein linked
exert effects indirectly by activating G-proteins in the membrane
32
Enzyme-linked receptors
binding by an enzyme causes conformational change`
33
homophilic binding
receptor in the membrane of one cell binds to the same receptor in the membrane of another cell
34
heterophilic binding
binding between different receptor types/ different cell types.
35
Fibroblast growth factor (FGF) family
simulates cell growth in fibroblasts. Activates the RTK pathway and the JAK-STAT pathway
36
Paracrine Signaling (Steps)
1. Paracrine factor is diffused, or moves through the ECM 2. Binds to a receptor 3. Initiates enzymatic reaction 4a. Regulates transcription factors 4b. Regulates cytoskeleton, influences shape and cell movement
37
RTK Pathway (Steps)
1. Ligand binds 2. Receptors dimerize 3. tyrosines get phosphorylated, changing their function due to a new negative charge 4. GAP and adaptor Proteins bind 5. Ras activation- phosphorylation changes a GDP for GTP 6. Phosphorylation and signaling cascade. 7. Movement of TFs into the nucleus 8. Changes in gene expression
38
JAK-STAT pathway
1. ligand (prolactin) binds to receptors that dimerize 2. reciprocal phosphorylation of JAK 3. JAK phosphorylates STAT which dimerizes 4. Complex moves into the nucleus and acts as a transcription factor 5. Upregulation of casein by upregulating proteins that bind to the casein mRNA and increase its half-life and prevent degredation
39
Ras
-Activates Raf -Activated through many signaling cascades -involved in cell cycle signaling -mutation of ras often causes cancer
40
Extracellular matrix
insoluble network of macromolecules that is secreted by cells forming a matrix around them
41
Function of the ECM
1. source of developmental signals 2. Different types of ECM are present in different tissues throughout the body 3. Cells make connections on the ECM so that they can move along it- facilitates cell migration
42
collagen
most abundant ECM protein fibers can bundle up and form tissues
43
Type 1 collagen
found in connective tissues
44
Type 2 collagen
found in cartilage
45
Type 4 Collagen
Forms the basement membrane epithelia
46
glycoproteins/ proteoglycans
normally contain ligands. Necessary for morphogenesis and differentiation Feedback between cells and the ECM
47
fibronectin
coating of fibronectin is mainly used in signaling many versions due to alternative splicing- this is a big gene also functions as an adhesive molecule, linking cells to one another and the ECM Aids in proper alignment of cells and cell migration as well
48
laminin
found only in the basement membrane
49
GAGs
-gives the matrix a soft consistency that resists compression -combines with proteins to form proteoglycan aggregates -hold a lot of water -chains of sugars
50
Basal lamina
closely knit sheets that underlie the epithelium, create a strong connection with cells - coats organs - holds tissues together
51
Sertoli cells experiment
Sertoli cells wont differentiate in and proliferate in response to Growth Factors unless on Basal Lamina coated plates -basal lamina triggers cell fates and identities - integrins trigger signaling as well
52
morphogens
any molecule that can lead to different cell fates when present at different concentrations
53
what controls responses to morphogens
1. Distance from the source 2. Amount of morphogen 3. Number of receptors on the cell
54
Morphogen experiment in Xenopus
-beads of activin places in xenopus cells -goosecoid expression at the highest threshold of the morphogen -xbra at the intermediate threshold -no signaling at the lowest threshold
55
Gradients of morphogens
provide positional identity and dictate cell fate/ identity
56
Modulators of Gradients
1. Endocytosis of nearby cells 2. Increasing the rate of decay of the messenger RNA 3. Binding of HSPGs 4. Activation of specific signaling transduction pathways by binding a ligand to its receptor 5. Transportation by filopodia cytonemes
57
Experiment: regulation endocytosis
Dynamin LOF decreases endocytosis and therefore lengthens the gradient- more morphogen is available for cells further away Rab5c GOF increases endocytosis, shortening the gradient as now less morphogen is available for cells further away
58
How do HSPGs regulate morphogen gradients
A. Sequester morphogens and prevent diffusion, shortening the gradient B. Help move morphogens further away from the source, lengthening the gradient
59
What are two mechanisms that regulate the amount of protein secreted from a cell
A. regulation of secretory and synthesis machinery B. regulation of mRNA decay
60
How can the extracellular surroundings of a cell influence the distance traveled and location of morphogens
A. HSPGs can move molecules either further away from the source, or keep them in the same place. B. Cytonemes can move morphogens throughout the tissue C. ECM facilitates diffusion and movement of morphogens
61
How can two identical cells respond differently to the same morphogen
They are at different locations in the tissue. Cells closer to the source experience higher concentrations of a morphogen, potentially allowing it to reach a different concentration threshold than a cell that is further away. This difference in concentration can alter cell fate.
62
How might two different cells respond differently to the same ligand
The same ligand might bind two different receptors, starting two different signaling cascades. Or, the ligand may bind to the same receptor, but the cells might respond to the signal with different proteins, resulting in the activation of two different signaling pathways.This leads to differences in intracellular signaling and eventually differences in gene expression
63
Which family of cell adhesion molecules is likely to be involves in the aggregation of cells
cadherins
64
What happens when cells are exposed to calcium-free media?
Cell types will no longer associate with each other and tissues will fall apart. This is because cadherins are calcium-dependent, and have extracellular motifs that require calcium in order to maintain the structure of cadherins.
65
T or F: Components of the ECM can serve as signaling ligands
True
66
T or F: Many different ligands can interact with distinct receptors in target cell membranes to activate signaling pathways
True
67
T or F: Endocrine signaling involves membrane bound ligands and receptors
False
68
T or F: Two cell types with the same receptor can be expected to respond similarly or identically to a given ligand
False
69
T or F: If all aspects of a cell are the same, they can still respond differently to an extracellular ligand binding a receptor on their surface
True
70
T or F: All growth factors work through a single cell signaling pathway
False
71
T or F: Signal transduction pathways regulate early development, primarily through transcriptional mechanisms
True
72
T or F: The specific events that occur during an induction event are determined by the cell that secretes the signal
False
73
T or F: the ability of a cell to respond to an inductive event varies based on stage of development, location within the embryo and potentially many other circumstances
True
74
What happens to the activity of cells when the ECM is degraded
Signaling completely shuts down- ECM facilitates signaling through binding with integrins. When the ECM is degraded, this signaling can no longer occur, preventing the transcription and translation of cell specific proteins. the cell then no longer acts as a differentiated tissue The cell therefore re-enters the cell cycle, and is no longer a differentiated cell
75
The integrin receptor connects a cell's cytoskeleton with
the extracellular matrix
76
During the epithelial-mesenchyme connection:
1. integrins disconnect from the basal lamina 2. cells begin to move 3. actin filaments break down
77
Specificity and strength of cell adhesion are dependent upon:
A. type of adhesion proteins B. number of adhesion proteins
78
The extracellular matrix participates in cell signaling by:
A. absorbing signaling molecules B. facilitating signaling molecule diffusion C. providing target sites for binding integrin, a signal receptor
79
Regulative or conditional specification is facilitated by:
A. cell signaling B. cell-cell interactions C. ECM interactions

Module Assessment 2: Cell Signaling (1 decks)

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