Cell Signaling Flashcards
5-3, 6-1
What is cell signalling?
The process by which cells communicate with eash other and the environment, cell signaling changes cell behavior
What discoveries have come from an improved understanding of cell signalling?
Improved understanding of communication with our environment (smell, touch, etc), therapies for cardiac failure, hypertension, tissue engineering
What internal signals change cell behavior?
Hormones, Nutrients, Neurotransmitters, metabolities
What external signals change cell behaviour?
Nutrients, toxins, sensory cues
What is an autocrine signal?
when a cell signals itself
What is a paracrine signal?
When a cell signals its neighbour
What is an endocrine signal?
When a cell signals a cell far away (signal travels through circulatory signal)
What are the basic steps of cell signalling?
- Initiation
- Propagation
- Amplification
- Cellular Response
- Termination
What happens during initiation? (Cell signalling)
A signal binds to a receptor on a cell
What happens during propagation? (Cell signalling)
Signalling protein is triggered inside cell
What happens during amplification? (Cell signalling)
signalling protein triggers other signalling proteins
What happens during cellular response? (Cell signalling)
Effector proteins cause a change in behaviour
What happens during termination? (Cell signalling)
Cell stops response
Is the speed of cell response uniform?
No, it can be fast or slow
What are the two main classes of cell signals?
Long Range (Endocrine), Short Range (Paracrine and Endocrine)
What are characteristics of Long Range signals?
Signals are typically produced far from the target tissue, endocrine signals circulate through the animal
What are characteristics of Short range signals?
Act on short distances, use paracrine / autocrine singaling
What is Synaptic signalling?
Pre synaptic cell releases transmitters which trigger post - synaptic cell
What is contact cell signaling?
Protein from inside of signalling cell hangs outside cell and triggers proteins on outside of target cell
What is an example of an endocrine signal?
Adrenaline, released from the adrenal gland, travels through the blood and signals the whole body
Do all cells respond to all signals?
No - a cell can only respond to a signal if the cell expresses a receptor for that signal
Can there be multiple receptors for a single signal?
Yes, Acetylcholine can cause salivation, skeletal muscle contraction, and decreasing heart rate
What are the two classes of signal receptors?
Cell surface, intracellular
How do cell surface receptor work?
They interact with a receptor protein which initiates a intracellular signalling cascade which creates change in cell
How to intracellular cell receptors work?
They diffuse through plasma membrane, interact with a receptor protein and directly change the function of a cell (ie. cortisol)
How do cells make decisions when integrating multiple signals?
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What are the three types of cell - surface receptors?
Ion-channel coupled, g-protein coupled, enzyme linked
How do pre - synaptic cells interact with post - synaptic cells in ion channel coupled receptors?
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Discuss the changes to membrane potential, opening voltage gated channels, propagating signal
down the neuron and stimulating exocytosis of new neurotransmitters to the next neuron
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What are the 4 features of GPCRs?
- Transverse the membrane as 7 alpha helices
- 7000 Members in the family
- Signals that bind to GPCRs include hormones, neurotransmitters, fatty acids, proteins, odourants, etc
- Amenable to pharmacological manipulation
What do the GPCR and G protein subunits sub-units (α, β, γ) look like at rest?
α subunit binds to GDP, α and γ are tethered to cell membrane
What happens at initiation in GPCRs signal through G proteins?
signal / ligand binds to CPCR on outside of cell which causes α to associate with GDP, α dissociates from β and γ
What happens at propagation in GPCRs signal through G proteins?
α and βγ subunits of G proteins associate with many
targets
What happens at amplification in GPCRs signal through G proteins?
Activated G proteins associate with enzymes which trigger second messenger
What are examples of second messengers in GCPR cell signalling?
cyclic AMP, inositol triphosphate, diacylglycerol, Ca2+, cyclic GMP
Describe how cAMP is involved in signal amplification
adenylyl cyclase produces cAMP and phospholipase C,
Identify two features of an enzyme-linked receptor
Often have only a single transmembrane
pass, and alpha helix , Signals that activate enzyme-linked
receptors include hormones and growth
factors
Describe the sequence of events that occurs
after a signal binds to an enzyme-linked receptor
- Receptor tyrosine kinases dimerize upon ligand binding, Dimerization induces receptor tyrosine kinase activity 2. Activated receptor recruits many proteins 3. Receptor-associated proteins amplify the signal, Several enzyme-linked receptors activate GTPase Ras 4. Activation of Ras has diverse effects on cellular proteins and transcription to change cell behaviour 5. Protein tyrosine phosphatases terminate the signal
Compare and contrast cell signaling mediated by GPCRs and enzyme-linked receptors
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Name two diseases linked with GPCRs
Hypertension, congestive
heart failure
Name two diseases linked with enzyme-linked receptors
Congenital growth
disorders
§ Craniosynostosis
