1 - Interpreting Extracellular Signals & Signal Transduction Flashcards
What does signal transduction involve (two basic components)?
A signal in, and a signal out
For signal transduction, what is the most common and general kind of input signal?
Extracellular signaling molecule
For signal transduction, what is the most common and general kind of output signal?
Intracellular signaling molecule
What questions are involved in signal transduction (in terms of the signals) (4 general questions)?
- How are signals generated and released?
- How are signals perceived by the recipient?
- How is the response to the signal generated?
- How are multiple signals integrated?
What questions are involved in chemical messengers (3 general questions)?
- How does it mediate a response in a particular cell type?
- How does it mediate pleiotropic responses? (different effects by same chemical messenger)
- How does it mediate different responses in different targets?
How can chemical messengers be regulated (general mechanisms)?
Synthesis, packaging, secretion, and degradation
Why is cell signaling important?
Controls almost every aspect of cell structure and function, need to respond to environment, etc.
What processes does cell signaling regulate?
Growth and division
What field of biology was useful for studying cell signaling?
Virology
Why is virology useful for studying cell signaling?
Viruses need to infect cells to function, so by studying viruses, we learned about the basics of cells
What are some examples of extracellular signals?
Hormones, pheromones, heat, cold, light, osmotic pressure, concentration changes of glucose, K+, Ca2+, cAMP
What are some examples of intracellular signals?
Modification of metabolism, production and degradation of substances, phosphorylation, activation and inhibition of reactions
What are the 5 general principles of cell signaling?
- Signals act over different ranges
- Signals have different chemical natures
- The same signal can induce a different response in different cells
- Cells respond to sets of signals
- Receptors relay signals via intracellular signaling cascades
What does it mean that signals act over different ranges?
Different spatial capabilities of the signals (local vs endocrine, etc.)
What does it mean that signals have different chemical natures?
Different structures of the different signals lead to different functions
How can the same signal induce a different response in different cells?
Different receptors and relay cascades (found in different cells) can cause a different output based on a signaling input
What does it mean that cells respond to sets of signals?
The cell integrates multiple signals over space and time to produce a particular response
What is the advantage of relaying signals via intracellular signaling cascades?
More amplification, which allows for a large response from a small amount of signaling molecule
What do sensors do?
Detect the external signals in the environment
What do the internal logic circuits do?
Responds to the inputs, and decided what is the proper response
What do actuators do?
The final step in the pathway to produce a response (cell movement, growth, chemicals, etc.)
Why is timing important in cell signaling?
Different responses could need a fast or slow response, a sustained response, or a degrading response. Thus, the timing is important based on the stimulus
What is the time scale of altering protein function?
Fast (sec to min)
What is the time scale of altering gene expression?
Slow (min to hour)
Why is altering protein function fast?
Proteins are already in the cytoplasm to be modified
Why is altering gene expression slow?
Need all the machinery to create new proteins and alter protein levels
What is the range of endocrine signaling?
Long range (through bloodstream)
What is the range of paracrine signaling?
Local (close neighbors)
What is the range of neuronal or synaptic signaling?
Synapse of two neurons or other cells
What is the range of cell-cell recognition?
Direct contact
What are some examples of endocrine signaling molecules?
Estrogen, epinepherin
What are some examples of paracrine signaling molecules?
Nitric oxide, histamines, prostaglandins
What are some examples of neuronal signaling molecules?
Neurotransmitters (GABA, dopamine, etc.)
What are some examples of cell-cell recognition signaling molecules?
Delta/notch
What is autocrine signaling?
A cell releases a signal, which can bind to its own receptors and cause a response
What does acetylcholine do to heart pacemakers cells?
Decreases rate of firing
What does acetylcholine do to salivary gland cells?
Secretion of chemicals in vesicles
What does acetylcholine do to skeletal muscle cells?
Contraction
How can acetylcholine lead to different responses in heart, salivary, and skeletal muscle cells?
Different detection (receptors) and intracellular cascades (downstream signals) lead to different responses
What are some examples of classes of extracellular signals?
Small molecules, gases, steroids, eicosanoids, peptides
What are some examples of receptor types?
G-protein coupled receptors (GPCRs), receptor protein-tyrosine kinases (RTKs), ligand gated channels, steroid hormone receptors, specific receptors (B and T cell receptors)
What are some examples of small molecules as extracellular signals?
Amino acids and their derivatives, such as acetylcholine, epinepherine, and dopamine
What are some examples of gases as extracellular signals?
Nitric oxide (NO) and carbon monoxide (CO)
What do steroids regulate?
Sexual differentiation, pregnancy, carbohydrate metabolism
What are eicosanoids?
Lipids derived from fatty acids (extracellular signal)
What are the 4 properties of signaling molecules?
Specificity, amplification, adaptation/desensitization, and integration
What is meant by specificity (for signaling molecules)?
A signaling molecule fits into one binding site, and other signals do not fit
What is meant by amplification (for signaling molecules)?
Enzymes can affect multiple copies of other enzymes, which causes a geometric increase of affected molecules
What is meant by adaptation or desensitization (for signaling molecules)?
Make the receptor no longer respond to the signal
What is the advantage of adaptation/desensitization?
Feedback to the system, make sure it can be turned off
What is meant by integration (for signaling molecules)?
The cell can combine multiple inputs to lead to an appropriate response
What is a molecular signaling device?
A molecular change leads to a molecular response
What is a network signaling device?
Multiple proteins interact based on a signal to generate a response
What is a cellular signaling device?
The entire cells receives signals, and generated an overall cellular response
What is the different between a molecular, network, and cellular signaling device?
Size and scope of the signaling
What is the purpose of a receptor?
Relay information about the extracellular environment to the intercellular environment
What are effector proteins?
Proteins that mediate the appropriate response (last step in the cascade)
How stable is cell signaling (response)?
Transient changes (min to hours)
How stable is gene expression (response)?
Stable (hours to years)
What is the energetic cost of cell signaling (compared to gene expression)?
Energetically cheaper
What is the energetic cost of gene expression?
Energetically expensive
Why is gene expression more energetically costly than cell signaling?
Needs transcription and translation machinery
Why is cell signaling less energetically costly than gene expression?
Not changing protein synthesis / expression
What are the 4 ways that proteins in cells can respond to signals?
Binding/dissociation, post-translational modification, conformational change, and localization
What is binding/dissociation?
Two molecules coming together / apart
What is conformational change?
Change in the structure of a protein or other molecule
What is a post-translational modification?
Add another molecule to the outside of a first molecule to change its function
What is localization?
One molecules moves to a different part of the cell, thus changing the signal pathway
How does amplification work?
A protein activates multiple copies of the next component in the pathway
Why are signaling cascades used for amplification?
Allows for multiple steps, which can be amplified
What is the importance of amplification?
A single molecular event can lead to 1,000,000 active control factors
What is bacterial chemotaxis?
Movement based on a chemical
What would a bacterium do if there was no stimulant present?
Move in a random walk
What would a bacterium do if there was a positive stimulant present?
Move towards the stimulant
What would a bacterium do if there was a negative stimulant present?
Move away from the stimulant
How do bacteria move?
Run and tumble motif
How do multicellular organisms use signal transduction?
Senses
What is meant by “structural heterogeneity of signaling molecules”?
Lots of different shapes of signaling molecules
What is the significance of “structural heterogeneity of signaling molecules”
Specificity towards one of many different kinds of receptors
What are the 5 types of chemical messengers?
Neurotransmitters, hormones, growth factors, cytokines, and growth hormones
How are chemical messengers regulated?
Synthesis, packaging, secretion, and degradation
What are neurotransmitters?
Chemical messengers found in the clefts of neurons
What type of signaling is neurotransmitters primarily used in?
Neuronal/synaptic signaling
What are cytokines?
Cell to cell signaling molecules that change gene activation or cellular function
What type of signaling is cytokines primarily used in?
Paracrine signaling
What are some stimuli that can induce cytokine expression?
Hypoxia, injury, seizures, inflammation, infection
True or false: cytokines are always advantageous
False: sometimes cytokines can protect, sometimes cytokines can cause damage
What are hormones?
Chemicals released into blood to different tissues
Where are hormones produced?
Glands
What type of signaling is hormones primarily used in?
Endocrine signaling
What is a growth factor?
A signaling molecule that directs growth
What process is growth factors important for?
Development (layers, axes, etc.)
What are growth hormones?
Hormones that are associated with growth
How is a class of chemical messenger determines (ex: neurotransmitter vs hormone)
What their target is, and how they’re moved around
Where are microtubules anchored?
At the centrosome
What signaling would homeostasis use?
Long term (maintain a constant state)
Why is autocrine signaling useful?
Use its own signal from an initial input to generate new receptors for a next expected input
What is an example of autocrine signaling?
Immune system, extracellular matrix signaling (make ECM, which binds to receptor that responds to ECM that was made, making it move on to another phase), etc.
What is self-identity?
The cell knows what kind of cell it is
What signaling is used for self-identity?
Autocrine signaling
How do cancer cells use autocrine signaling?
Avoid cell cycle block (continuous division)
What is upstream signaling?
The cell that sends the signal would have an impact (response) based on the reception of the signal
What is downstream signaling?
The cell that receives the signal would have an impact (response) based on the reception of the signal
How is evolution involved in cell signaling?
Create specific and fast signaling that is useful
What does DREADD stand for?
Designer Receptors Exclusively Activated by Designer Drugs
What do DREADDs do?
Synthetic GPCR that responds only to synthetic molecules
How can drugs take advantage of signaling pathways to solve a problem?
Drugs can turn down bad pathways, or turn up good pathways
Is cell signaling hereditary?
Yes. It can be passed down and selected upon
