Podcast
Questions and Answers
What is the role of autoinducers in quorum sensing?
What is the role of autoinducers in quorum sensing?
- To block the expression of the _lux_ operon.
- To degrade the cell membrane.
- To inhibit cell growth in confined environments.
- To activate the luminescent systems of bacteria at high cell density. (correct)
Which of the following components are directly involved in the activation of the lux operon in Vibrio fischeri?
Which of the following components are directly involved in the activation of the lux operon in Vibrio fischeri?
- Luciferase and the cell membrane.
- LuxR and Luciferase only.
- LuxI and Autoinducer (acyl homoserine lactone) only.
- LuxR and Autoinducer (acyl homoserine lactone). (correct)
What is the primary role of formin in yeast mating?
What is the primary role of formin in yeast mating?
- To activate the G protein.
- To polymerize actin microfilaments for shmoo projection formation. (correct)
- To dephosphorylate Fus3.
- To activate Fus3.
What is the first step in yeast mating upon encountering a mating factor?
What is the first step in yeast mating upon encountering a mating factor?
What is a key function of cell signaling in regulating the cytoskeleton?
What is a key function of cell signaling in regulating the cytoskeleton?
Which of the following describes the function of the Rho protein in cell migration?
Which of the following describes the function of the Rho protein in cell migration?
Which of the following is an example of long-distance cell signaling?
Which of the following is an example of long-distance cell signaling?
What characteristics describe a ligand-receptor interaction involving high ligand affinity?
What characteristics describe a ligand-receptor interaction involving high ligand affinity?
What differentiates antagonists from agonists in receptor binding?
What differentiates antagonists from agonists in receptor binding?
Which of the following is characteristic of cell-surface receptors?
Which of the following is characteristic of cell-surface receptors?
Which of the following molecules can function as an extracellular signal?
Which of the following molecules can function as an extracellular signal?
How does phosphorylation act as a molecular switch in cell signaling?
How does phosphorylation act as a molecular switch in cell signaling?
Which amino acids are commonly phosphorylated in cell signaling pathways?
Which amino acids are commonly phosphorylated in cell signaling pathways?
What is the role of GTPases in cell signaling?
What is the role of GTPases in cell signaling?
How do cells maintain specificity in signaling pathways despite the presence of closely related signaling molecules?
How do cells maintain specificity in signaling pathways despite the presence of closely related signaling molecules?
Why is signal amplification important in cell signaling pathways?
Why is signal amplification important in cell signaling pathways?
What is the function of a coincidence detector in cell signaling?
What is the function of a coincidence detector in cell signaling?
What is the role of scaffold proteins in signaling pathways?
What is the role of scaffold proteins in signaling pathways?
Which of the following statements best describes the role of protein domains in cell signaling?
Which of the following statements best describes the role of protein domains in cell signaling?
What is a key characteristic of adaptors in cell signaling?
What is a key characteristic of adaptors in cell signaling?
What mechanism increases local concentration of specific signaling molecules?
What mechanism increases local concentration of specific signaling molecules?
What happens to eukaryotic cells when signals A, B, and C are present?
What happens to eukaryotic cells when signals A, B, and C are present?
Which of the following is NOT a transmembrane protein?
Which of the following is NOT a transmembrane protein?
Which cell-signaling system allows the most approved drug targets?
Which cell-signaling system allows the most approved drug targets?
Which of the following is an example of bacterial communication?
Which of the following is an example of bacterial communication?
What are the requirements for a signal to be considered precise and specific?
What are the requirements for a signal to be considered precise and specific?
What is the purpose of the primary cilium?
What is the purpose of the primary cilium?
How does protein phosphorylation lead to reversible modifications?
How does protein phosphorylation lead to reversible modifications?
Which processes increases robustness?
Which processes increases robustness?
Which combination of signals will cause the eukaryotic cell to grow and divide?
Which combination of signals will cause the eukaryotic cell to grow and divide?
Which of the following is true regarding autoinducers?
Which of the following is true regarding autoinducers?
Which is true of quaternary structures?
Which is true of quaternary structures?
Where is a hydrophobic signal located?
Where is a hydrophobic signal located?
Which of the following is true of the extracellular signal?
Which of the following is true of the extracellular signal?
If a signal is short lived/ labile, what happens?
If a signal is short lived/ labile, what happens?
What is the shape of the shmoo in yeast mating?
What is the shape of the shmoo in yeast mating?
What is NOT a function of cell signalling?
What is NOT a function of cell signalling?
Which term is associated with the term transmembrane proteins?
Which term is associated with the term transmembrane proteins?
How does the presence of multiple extracellular signals influence a cell's fate?
How does the presence of multiple extracellular signals influence a cell's fate?
What is the significance of signal amplification in cell signaling pathways?
What is the significance of signal amplification in cell signaling pathways?
Labile and short-lived signals contribute to signal precision by doing what?
Labile and short-lived signals contribute to signal precision by doing what?
What role do coincidence detectors play in cell signaling pathways?
What role do coincidence detectors play in cell signaling pathways?
How do scaffold proteins enhance the specificity of cell signaling pathways?
How do scaffold proteins enhance the specificity of cell signaling pathways?
What is a primary function of the primary cilium in cell signaling?
What is a primary function of the primary cilium in cell signaling?
Why is it important for cell signaling pathways to be reversible?
Why is it important for cell signaling pathways to be reversible?
How does protein phosphorylation act as a molecular switch in cell signaling?
How does protein phosphorylation act as a molecular switch in cell signaling?
What is the functional consequence of a cell's inability to regulate cell signaling pathways effectively?
What is the functional consequence of a cell's inability to regulate cell signaling pathways effectively?
What is the role of protein domains in cell signaling?
What is the role of protein domains in cell signaling?
How do adaptor proteins contribute to cell signaling?
How do adaptor proteins contribute to cell signaling?
What is the effect of scaffold proteins on the local concentration of signaling molecules?
What is the effect of scaffold proteins on the local concentration of signaling molecules?
How does high ligand affinity affect the dissociation constant (Kd) in ligand-receptor interactions?
How does high ligand affinity affect the dissociation constant (Kd) in ligand-receptor interactions?
What distinguishes antagonists from agonists in receptor binding interactions?
What distinguishes antagonists from agonists in receptor binding interactions?
What is the main function of a kinase?
What is the main function of a kinase?
What is the primary function of a GAP (GTPase-activating protein)?
What is the primary function of a GAP (GTPase-activating protein)?
What is the function of GEFs (guanine nucleotide exchange factors)?
What is the function of GEFs (guanine nucleotide exchange factors)?
Which amino acids are most commonly targeted for phosphorylation?
Which amino acids are most commonly targeted for phosphorylation?
How does a signaling pathway achieve precise control and specificity despite the presence of similar signaling molecules within the same cell?
How does a signaling pathway achieve precise control and specificity despite the presence of similar signaling molecules within the same cell?
How can cross-talk between signaling pathways impact cellular function?
How can cross-talk between signaling pathways impact cellular function?
What is the purpose of having signals that are short-lived or labile?
What is the purpose of having signals that are short-lived or labile?
How do cells prevent unwanted crosstalk between closely related signaling molecules?
How do cells prevent unwanted crosstalk between closely related signaling molecules?
What is the role of effector proteins in cell signaling?
What is the role of effector proteins in cell signaling?
Where are intracellular receptors typically located?
Where are intracellular receptors typically located?
What types of molecules can function as extracellular signals?
What types of molecules can function as extracellular signals?
Scaffold proteins increase the speed and efficiency of signaling pathways. What else do they do?
Scaffold proteins increase the speed and efficiency of signaling pathways. What else do they do?
How do protein domiains interact and affect each other?
How do protein domiains interact and affect each other?
WHich of the following is NOT an example of increasing specificity or robustness?
WHich of the following is NOT an example of increasing specificity or robustness?
What does an adaptor molecule do in cell-cell signalling?
What does an adaptor molecule do in cell-cell signalling?
WHich of the following increases the local concentration of signaling molecules?
WHich of the following increases the local concentration of signaling molecules?
What is a function of signal amplification?
What is a function of signal amplification?
How can a cell communicate across short distances?
How can a cell communicate across short distances?
What cell signaling mechanism can help increase specificity?
What cell signaling mechanism can help increase specificity?
According to structural modularity, what are signaling proteins built from?
According to structural modularity, what are signaling proteins built from?
What does the GEF protein promote?
What does the GEF protein promote?
Proteins that are GTPases that accelearte the GTPase activity of G Proteins convert what?
Proteins that are GTPases that accelearte the GTPase activity of G Proteins convert what?
What happens when a signal if short lived/ labile?
What happens when a signal if short lived/ labile?
What crucial role do short-lived signals play in ensuring precision in cell signaling?
What crucial role do short-lived signals play in ensuring precision in cell signaling?
How do cells prevent closely related signaling molecules from activating the wrong pathways?
How do cells prevent closely related signaling molecules from activating the wrong pathways?
In cell signaling, what advantage does signal amplification provide?
In cell signaling, what advantage does signal amplification provide?
How does the dissociation constant ($K_d$) relate to the affinity between a ligand and its receptor?
How does the dissociation constant ($K_d$) relate to the affinity between a ligand and its receptor?
What is the consequence of disrupting the balance between kinase and phosphatase activity in a cell?
What is the consequence of disrupting the balance between kinase and phosphatase activity in a cell?
How do coincidence detectors in cell signaling pathways enhance specificity?
How do coincidence detectors in cell signaling pathways enhance specificity?
What role do scaffold proteins play in ensuring specificity in cell signaling pathways?
What role do scaffold proteins play in ensuring specificity in cell signaling pathways?
How can cross-talk between different signaling pathways affect cellular outcomes?
How can cross-talk between different signaling pathways affect cellular outcomes?
A cell is exposed to a ligand that typically promotes cell growth but is also treated with an antagonist for a different receptor involved in cell survival. What is the most likely outcome?
A cell is exposed to a ligand that typically promotes cell growth but is also treated with an antagonist for a different receptor involved in cell survival. What is the most likely outcome?
What structural feature defines GPCRs (G-protein coupled receptors)?
What structural feature defines GPCRs (G-protein coupled receptors)?
Which feature of a signaling pathway will most directly determine its modularity?
Which feature of a signaling pathway will most directly determine its modularity?
What is primarily responsible for the diversity of cellular responses to a single extracellular signal?
What is primarily responsible for the diversity of cellular responses to a single extracellular signal?
What is a critical role for protein domains?
What is a critical role for protein domains?
How does receptor tyrosine kinase (RTK) activation typically initiate a signaling cascade?
How does receptor tyrosine kinase (RTK) activation typically initiate a signaling cascade?
What is the effect of a GEF (guanine nucleotide exchange factor) on G proteins?
What is the effect of a GEF (guanine nucleotide exchange factor) on G proteins?
What is the primary function of the adapter protein?
What is the primary function of the adapter protein?
What is the functional consequence of a mutation that impairs GEF activity?
What is the functional consequence of a mutation that impairs GEF activity?
What is the effect of a mutation that impairs protein's kinase ability?
What is the effect of a mutation that impairs protein's kinase ability?
Bacterial cells use quorum sensing to regulate certain behaviors based on population density. Which of the following is an example of a collective behavior regulated by quorum sensing?
Bacterial cells use quorum sensing to regulate certain behaviors based on population density. Which of the following is an example of a collective behavior regulated by quorum sensing?
How do eukaryotic cells maintain specificity in signaling pathways? How do they make sure that the correct signal is being delivered to the correct place?
How do eukaryotic cells maintain specificity in signaling pathways? How do they make sure that the correct signal is being delivered to the correct place?
Flashcards
Cell signalling
Cell signalling
A process where cells communicate with each other and their environment.
Quorum sensing
Quorum sensing
A regulatory system in bacteria where gene expression is coordinated based on population density.
Autoinducers
Autoinducers
Molecules produced by bacteria. Diffuse through the cell membrane into growth media.
LuxR
LuxR
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Luciferase
Luciferase
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Budding yeast
Budding yeast
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Mating factor
Mating factor
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Shmoo formation
Shmoo formation
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Cell signalling
Cell signalling
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Receptor proteins
Receptor proteins
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Ligand
Ligand
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Intracellular signalling proteins
Intracellular signalling proteins
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Effector proteins
Effector proteins
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Contact-dependent signals
Contact-dependent signals
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Paracrine signals
Paracrine signals
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Autocrine signals
Autocrine signals
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Endocrine signals
Endocrine signals
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Neurotransmitters
Neurotransmitters
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Agonists
Agonists
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Antagonists
Antagonists
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Receptor affinity
Receptor affinity
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Ligand-gated ion channels
Ligand-gated ion channels
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G-protein-coupled receptors (GPCRs)
G-protein-coupled receptors (GPCRs)
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Enzyme-coupled receptors
Enzyme-coupled receptors
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Receptor tyrosine kinases (RTKs)
Receptor tyrosine kinases (RTKs)
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Second messengers
Second messengers
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Molecular switches
Molecular switches
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Phosphorylation
Phosphorylation
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Protein kinases
Protein kinases
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Protein phosphatases
Protein phosphatases
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GTPases
GTPases
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Phosphorylation cascade
Phosphorylation cascade
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Protein domains
Protein domains
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Modularity
Modularity
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High affinity
High affinity
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Signal amplification
Signal amplification
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Labile signals
Labile signals
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Coincidence detection
Coincidence detection
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Scaffolding
Scaffolding
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Study Notes
Cell Signalling Overview
- Cells communicate with each other and their environment, affecting processes like cell migration.
- Cell signaling regulates cytoskeleton function, influencing development, differentiation, cell division, and energy metabolism, ultimately resulting in chemical and physical changes.
- Cell communication is vital for body to survive.
External Signaling and Cell Migration
- External signals dictate the direction of cell migration.
- Neutrophils move towards chemical attractants like bacteria.
- The Rho protein dominates at the back of the cell, prompting actin-myosin contraction.
- The Rac protein dominates cell front, resulting in polymerization, also known as protrusion.
Quorum Sensing
- Quorum sensing allows bacteria to communicate, like in Vibrio fischeri.
- Vibrio fischeri glows in Hawaiian Bobtail Squid only when cell density are high.
- As cell growth continues, the level of autoinducers in media accumulates.
- Quorum sensing is a regulatory response to high cell density.
- Autoinducers include acyl homoserine lactone.
- High levels of autoinducers activate the lux operon prompting bioluminescence.
- Quorum sensing manages collective behaviors in bacteria like antibiotic production, biofilm formation, and virulence factors.
Cell Communication in Yeast
- Yeast cells of different mating types signal using a and alpha factors to exchange mating factors.
- This exchange leads to shmoo formation, ultimately resulting in mating.
- Shmoo projection forming results in binding at the G protein-coupled receptor.
- Formin initiates microfilament growth that forms shmoo projections.
General Signalling
- Signalling systems govern various cell and tissue functions during development and adulthood.
- The main signaling elements include extracellular signal molecules (ligands), receptor proteins, intracellular signaling proteins, and effector proteins.
- A limited amount of extracellular signaling molecules can trigger a high number of responses.
- Responses rely on combinations of extracellular signals and availability of signalling elements.
- Signalling is classified as contact-dependent, paracrine (+ autocrine), synaptic, or endocrine.
Signals
- Signals are proteins, small peptides, amino acids, small molecules, steroids, fatty acid derivatives, gases (NO, CO2, Ethylene), or nucleic acids.
- Signals attach to the surface of a cell, gets released into the extracellular space by diffusion or exocytosis, or can be soluble or bound to the extracellular matrix.
- Extracellular signals attach to receptors on the surface of the cell (cell surface receptors).
- In the case of hydrophobic signals, they attach in the interior of the cell (intracellular receptors).
- Signals can stimulate or inhibit a signaling pathway.
Receptor-Ligand Binding
- Binding of a receptor and ligand resembles the binding of an enzyme and its substrate.
- Ligand and receptor binding kinetics is similar to enzyme reaction kinetics.
- Receptors with high ligand affinity have low dissociation constant (Kd).
- Agonists are drugs that trigger receptor activation when bound.
- Antagonists bind receptors, but don't trigger activation.
- Angiotensin II receptor blockers function as antagonists to treat hypertension.
Extracellular Signal Effects
- Extracellular signals result in cell movement, cell division, cell death, cell differentiation and development.
- Extracellular signals themselves provide little information on the cellular response.
- The signal output heavily relies on the availability of receptors, intracellular signaling molecules, and effector proteins.
Cell-Surface Receptor Proteins
- The three major classes of cell-surface receptor proteins are ion channel-coupled receptors, G protein-coupled receptors (GPCR), and enzyme-coupled receptors.
- Ion channel-coupled receptors enable rapid synaptic signaling between nerve/muscle cells through transmembrane proteins.
- GPCRs use a trimeric GTP-binding protein (G protein) to relay the signal to a target protein, being either an enzyme or an ion channel.
- Enzyme-coupled receptors are single-pass transmembrane proteins.
- When enzyme-coupled receptors bind a ligand on the outside, an enzyme or enzyme binding site is present on the inside.
- More often the enzyme of an enzyme-coupled receptor is a kinase, known as Receptor Tyrosine Kinases (RTKs)
Molecular Switches
- Many intracellular signalling proteins function as molecular switches.
- Reversible protein modifications, like phosphorylation, enable these switches.
- Switches are controlled via phosphorylation/dephosphorylation, using protein kinases and protein phosphatases.
- Switches can turn ON or OFF.
- Amino acids that can be phosphorylated: Tyrosine (Tyr or Y), Threonine (Thr or T), Serine (Ser or S).
- GTPases function as molecular switches via GTP binding and hydrolysis, they can be small monomeric or large trimeric.
- Small monomeric switch proteins use GTPase activating protein GAP and GTP Exchange Factor GEF as cofactors.
Ensuring Siginal Specificity
- Closely related signalling molecules can bind to the wrong partner, creating noise and unwanted cross-talk between signalling pathways.
- In order to prevent this issues, signals are made with high specificity, low noise and/or limited cross-talk between pathways..
- Specificity is achieved through signal-ligand interactions and high-affinity interactions.
- Signal amplification allows a single molecule to activate many downstream molecules for a bigger response and prevent false responses, also known as reduced noise.
- Short-lived signals reduce background noise.
- Coincidence detectors increase specificity.
- Scaffolding brings signaling proteins in close proximity, allows them to form complexes, concentrating them in cells.
Primary Cilia
- Primary cilium is the antenna of the cell, it concentrates receptors and signalling molecules.
- Modularity also helps ensure signal specificity.
- Protein domains are modules on a polypeptide with specific functions consisting of protein sequences and tertiary structures.
- Examples of interaction domains: SH2 (binds to phosphotyrosine), PTB (phosphotyrosine binding domain), SH3 (Short proline rich sequences), PH (charged head groups of specific phosphoinositides).
- Adaptors are small and have two binding regions to target the action of two bound enzymes.
- Scaffolds are large multidomain proteins with structural disorder, able to regulate several members of a signalling pathway.
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