Lecture 7 Flashcards
How does cell signalling cause cell responses?
- by changing the amount or activity of specific proteins
- alter gene expression for specific protein
- alter activity of specific protein
Information from DNA is used to produce a ___
Using _____ and _____
Protein
Translation
Transcription
Fundamental of gene expression
Using information from DNA to make a protein
Two stages of gene expression
Transcription - making RNA copy of DNA sequence
Translation - RNA info used to synthesise the protein
Diagram of gene expression
What part of gene expression does cell signalling target?
Either transcription (pathway can go into the nucleus) or translation
(We can turn genes on and off - make proteins or not make proteins)
Transcription factors turn genes ___ and ____
On and off
What is a transcription factor
- proteins that bind to specific regions on DNA and regulate gene expresssion
What is a transaction factor that promotes transcription called?
Activator
What is the transcription factor that supptresses transcription called?
Repressor
Transcription factors ensure
The right gene is going to expressed in the right cell at the right time in response to an appropriate signal
3 ways that the transcription factors are regulated
- Synthesis (another TF will regulate the transcription of a TF)
- Localisation (some are found in the nucleaus, some in cytoplasm that translocate in - where a transcription factor is located is going to impact whether a TF can do its job or not)
- Activation (turn protein on)
E.g ligand binding (nuclear recptors)
E.g phosphorylation
Process of regulating gene expression using TF
What happens in cell proliferation and growth
Increase number of cells
Signal to prolfiferate is received during _____
G1 phase
How does a cell proliferate and grow
- signal to proliferate received during G1 phase (this promotes it to move onto S phase)
- involves activation of Cyclin-dependent kinases
- serine/theonine kinases
- activated by cyclin
- which activate transcription factors that promote entry into S phase
What happens after growth factor binds to receptor?
- activates intracellular phosphorylation cascade
- phosphorylation of MNK1
- activates ERK2
- phosphorylation of c-Myc
What are metabolic processes ?
- chemical reactions needed for cell to stay alive
How can signalling pathways impact metabolic processes?
- increase uptake and utilisation of nutrients
- regulate enzymes involved in cellular metabolism
How adrenaline alters metabolic pathways - specifically in muscle?
- adrenaline binds GPCR (GDP to GTP, alpha subunit binds adenylyl cyclase, turning ATP into cyclic AMP)
- cAMP concentration increase activates PKA (PKA can enter into nucleus, activate the TF and upregulate transcription)
- PKA will also act of two key enzymes in the cytoplasm:
- Glycogen phosphorylase (phosphorlated by PKA)
- turns glycogen into glucose
- phosphorylation activates - Glycogen synthase (phospharlyted by PKA)
- turns glucose into gycogen
- phosphorylation inhibits its enzyme activity
What is apoptosis
- programmed cell death (via signals)
- highly controlled
- for damaged or unneeded cells
(Don’t want travel to travel to a new environment where it could cause harm - will kill cell if detatched from where it should be)
Two pathways for apoptosis
- intrinsic (mitochondrial)
- extrinsic (death receptor)
What signaling causes apoptosis?
- Fas ligand binds to Fas receptor
- TNF receptor
- receptor trimerises (3 come together)
- binds FADD
- forms DISC (death inducing signal complex)
- Activates caspases
- which causes events of apoptosis
Note: there is cross talk between extrinsic and extrinsic signalling
What are stem cells?
Undifferentiated cels
________ determine what stem cells will become
Signals
In stem cell delveopmet there are numerous ____ many _____ and many____
Pathways
Ligands
Receptors
What is the process when the embryo cell divide into 3 different tissue types called?
Gastrulation
What 3 tissues result from the process of gastrulation
- ectoderm
- endoderm
- mesoderm
(All multipotent)
What signal pathways form what parts of gastrulation ?
Wnt and TGFB: endoderm
BMP: mesoderm
Inhibition of these: ectoderm
Signalling and embryonic development - how did everything know where to form?
- using shh (sonic hedgehog)
- a signalling protein that regulates embryonic morphogenesis (how the embryo forms the shape it needs to become)
- important for limb development - how much shh is in each limb determines how and where it’ll grow?
Multiple responses can happen at same time
Cells have multiple receptors receiving multiple signals at the same time
How do we ensure that the binding of one little signal molecules on the receptor can have some big effects?
- amplification
- amplification is making the signal bigger inside the cell
What is cross talk
When one or more components of a pathway can affect another pathway:
Cross talk may:
- stimulate
- inhibit
- only active is two pathways work together
Two ways of feedback
- internal feedback
- external feedback
5 types of feedback
Probs wont be in exam
Receptor down regulation
- type of negative feedback
- membrane receptors become endocytosed
- ligand unable to bind and activate pathway
How we can stop a cell responding from an external signal
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