Module 5A - Cell Signaling Flashcards
Mechanism of the cell to respond towards physical and chemical changes in the environement.
Cell signaling
A type of signaling where the cell produces their own signaling molecules.
Autocrine signaling
A type of signaling where chemical synapses are produced by neurons and delivered through neurotransmitters
Synaptic signalling
A type of signaling where the signaling molecules are produced by the endocrine system that travels through the bloodstream to reach the target cells.
Endocrine signaling
A process where cells communicate with one another in response to an external stimuli, transferring information from one cell to another.
Cell signaling
Cells communicate by using:
Extracellular signaling molecules
Type of cells that responds to the specific extracellular signaling molecules.
Target cells
Found in the surface of target cells that receive the signal molecules.
High specificity-binding sites
Types of extracellular signals:
Stimulatory or inhibitory signals
Cells are programmed to respond to ___________________ that determines how it would integrate all signaling information in order to make decisions.
Specific combinations of extracellular signals
An effect of a signaling molecule changes based on:
- Different types of target cells
- Different intracellular signaling proteins
- Distinct effector proteins
- Genes
Induces the cell to respond based on its pre-determined state.
Signal molecule
Three(3) major classes of cell-surface receptor proteins.
- Ion-channel coupled receptors
- G-protein couple receptors
- Enzyme-couple receptors
Converts the extracellular signals into intracellular signals that changes the behavior of the cell.
Signal transducers
A major class of surface receptor, where the signaling molecule activates a trimeric GTP-binding protein (g-protein)
G-protein couple receptors
A type of cell-surface receptor that directly opens or closes in response to the binding of a specific ligand.
Ion-channel coupled receptors
Cell surface receptor that also functions as an enzyme or associated directly with enzymes.
Enzyme-coupled receptors
Type of cell surface receptor with a ligand-binding site on the extracellular and an enzyme-binding site in the intracellular space.
Enzyme-couple receptors
Cell surface receptor that is associated with electrically excitable cells and neurotransmitters.
Ion-channel coupled receptors
Cell surface receptor that activates a specific protein (g-protein) that carriers the signal towards the intracellular matrix.
G-protein coupled receptors
Binds and alters the behavior of selected signaling or effector proteins. Considered as molecular switches.
Intracellular signaling molecules
Made up of small chemicals, water-soluble molecules, or lipid-soluble molecules that alters the behavior of selected effector proteins.
Intracellular signaling molecules
Type of intracellular signaling that uses phosphorylation (addition of a phosphate group).
Signaling by phosphorylation
Enzyme that catalyzes the addition of a phosphate group (phosphorylation).
Kinase
Enzyme that catalyzes the removal of a phosphate group (dephosphorylation).
Phosphatase
There are ____ kinases, and ____ phosphatases.
520, 150
Signaling by GTP-binding is turned on by binding of ____, and is turned off by the binding of ____.
GTP, GDP
Proteins that facilitated the hydrolysis of GTP.
GTPase-activating proteins
Releases the binding of GDP on the effector protein.
Guanine nucleotide exchange factors (GEFs)
Signaling by GTP-binding is considered as a:
Double-negative activation
Activation caused by intracellular signaling molecules are determined by:
High affinity and specificity
Holds the protein in close proximity; interact at high local concentration; sequentially activated rapidly.
Signaling complexes
Serves as the docking site or binding site of signaling molecules.
Phosphorylated cytoplasmic tail
Recruits specific intracellular signaling proteins.
Phosphoinositides
7 principles of cell signaling:
- Response
- Sensitivity
- Dynamic range
- Persistence
- Signal processing
- Integration
- Coordination
Depends on the nature of intracellular signaling molecules.
Speed of response
Smoothly graded response and the concentration rises beyond the threshold value.
Hyperbolic
Rates of responses based on the concentration of signal molecule.
Hyperbolic, all-or-none, sigmoidal
The output of the process that acts back to regulate the same process.
Feedback loops
Feedback in which the output stimulates its own production.
Positive feedback
Feedback where the output inhibits its own production.
Negative feedback
Steepen the process of output production creating a sigmoidal or all-or-none curve. Can exist in either a “switched off” or “switched on” state.
Positive feedback
A transient extracellular signal that can induce long-term changes (e.g. muscle-cell specification)
Positive feedback
Counteracts the effects of a stimulus.
Negative feedback
Limits the level of response which causes delay or oscillations.
Negative feedback
A decrease in the response to a specific stimulus due to prolonged exposure caused by a strong response that reset the machinery to become less responsive.
Adaptation/Desensitization
A single polypeptide chain that threads back and forth across the lipid bilayer seven times, forming a cylindrical structure.
G-protein coupled receptors
Largest family of cell-surface receptors and uses g-proteins to relay extracellular signals.
G-protein coupled receptors
Three(3) subunits of GTP-binding proteins
α , β, and γ
α-subunit has GDP-bound and the g-protein is inactive.
Unstimulated
α-subunit release its bound GDP →
binding of GTP → conformational
changes → dissociation of the GTP-bound Gα subunit from the Gβγ pair
Activation
G-proteins regulate the production of this protein.
cyclic AMP
Stimulatory g-proteins activate this protein
adenylyl cyclase
Cause by ADP ribosylation that alters the stimulatory g-protein α-subunit.
Cholera toxin (cholera)
Results from the ADP ribosylation of the α-subunit of inhibitory g-protein.
Pertussis toxin (whooping cough)
Phosphorylates specific serine or threonine; regulating their activity.
cyclic-AMP dependent protein kinase (PKA)
The inactive state of PKA
Two catalytic and regulatory subunits
Active state of PKA
Releases catalytic subunits
cAMP activates the hormone that encodes this protein.
Somatostatin
Stimulates the cellular gene expression after phosphorylation at a conserved serine in response to cAMP.
cyclic AMP response element (CRE)
Regulates the expression of cyclic AMP response element before it reaches the transcription site.
CRE-binding protein (CREB protein)
An active protein kinase C (PKC)
Diacyglycerol
G-protein that catalyzes the regulation of the actin cytoskeleton
G12
Smell and vision depends on ______ that regulated the ion channels.
GPCR’s
