Cell Signaling Flashcards
(36 cards)
What are the three stages of cell signaling:
1.Reception- signaling molecule, also called a ligand (like a hormone or neurotransmitter), binds to a specific receptor protein on the surface of the target cell or sometimes inside the cell.
The receptor is like a lock, and the ligand is like a key—only the right ligand can bind to and activate the receptor.
2. Transduction-Once the ligand binds to the receptor (reception), the receptor changes shape or becomes activated. This sets off a cascade of events inside the cell, called signal transduction and activates intercellular molecules via secondary messengers
Think of it like dominoes falling—one protein activates another, which activates another, and so on. This series of changes amplifies the signal and passes it deeper into the cell.
3. Cell response to the signal
State the Classes of transmembrane receptors
And give three examples for each
1.G protein coupled receptors: Epinephrine (Adrenaline) • Dopamine • Histamine
Peptide and amino acid–derived hormones like epinephrine, norepinephrine, glucagon, vasopressin
• Neurotransmitters like dopamine, serotonin, histamine
• Odorants, light, and other sensory molecules
2.Enzyme coupled receptors: Epidermal Growth Factor (EGF)
• Insulin
• Platelet-Derived Growth Factor (PDGF)
3.Ion channel receptors : Acetylcholine — Nicotinic Acetylcholine Receptor (Na⁺ channel)
• GABA (gamma-aminobutyric acid) — GABA_A receptor (Cl⁻ channel)
• Glutamate — NMDA receptor (Ca²⁺ channel)
How do G protein coupled receptors work?
There are three types of G proteins. State them. Which activates phospholipase c and what does activating phospholipase C do?
G protein coupled receptors: have seven pass transmembrane teceptors. The end of the GPCR that’s in the cell activates intracellular proteins called guanine nucleotide binding proteins. G proteins are made up of alpha beta and gamma. Alpha and gamma units are anchored to the cell membrane and keep the G protein right next to the receptor. G proteins bind to guanine diphosphate (GDP) when they’re inactive.
When a ligand binds, the GPCR changes its shape and makes the G protein to release GDP and bind to GTP instead. This activates the protein. When the alpha subunit is bound to GtP and not GdP, it separates from the beta and gamma subunits.
It stimulates some molecules while inhibiting others.
To act on other subunits, the alpha subunit turn GTP into GdP and this makes the three subunits come together again and the G protein is turned of
Types of G proteins:
Gq(subscript), Gi (subscript),Gs(subscript)
Gq activates phospholipase C which is in the cell membrane. This lipase C cleaves a phospholipid called phosphatidyl inositol 4,5 bisphosphate jnto inositol triphosphate(IP) and DAG(diacylglycerol).
Inositol triphosphate is soluble and diffuses through the cytoplasm and into the endoplasmic reticulum where it opens up calcium channels.
Because now calcium is higher in the ER than the cytosol, calcium flows out into the cytosol
The increased calcium in the cytoplasm can lead to depolarization.
DAG remains attached to the cell membrane and binds to a protein called kinase C which relies on calcium to fully activate. Increased calcium in the cells makes protein kinase C phosphorylate proteins to make them active
There are three types of G proteins. Which activates adenylate cyclase?
What happens when it’s activated?
Which of them causes a negative feedback?
Gs protein.
Activated adenylate cyclase takes ATp and removed two phosphates molecules changing it to cyclic adenosine monophosphate(cAMP)
cAMP moves into the cytoplasm and binds to protein kinase A.
Protein kinase A has two parts: a regulatory protein subunit and a catalytic subunit.
cAMP binds to the regulatory subunit and makes it dissociate from the catalytic subunit.
When the catalytic subunit is free, it goes to phosphorylate target proteins and trigger cellular response
Protein Gi is bound to adenylate cyclase but it inhibits it causing negative feedback on protein Gs and this is important for inactivating cells.
What type of transmembrane proteins are single pass protein segments?
Enzyme coupled receptors.they have their intracellular end having intrinsic enzyme activity
Enzyme coupled receptors have two parts. Name them.
State the three main types of enzyme coupled receptors and explain how they work
Receptor domain
Enzyme domain: usually a protein kinase that phosphorylates the receptor domain
Note that when it comes to signals, phosphorylation turns it on but when it comes to metabolic pathways, phosphorylation turns them off cuz they want to stop over production.
The types are based on the amino acid at which the receptor is phosphorylated.
1. Receptor tyrosine kinase: most common type. They can’t phosphorylate their own tyrosine side chains.
When a ligand binds on this receptor, two receptors come together and dimerize. They cross phosphorylate on one another at multiple tyrosine residues and this triggers a conformational change that creates high affinity binding sites for the secondary messengers which can also be activated via phosphorylation this triggering the signaling pathway
2. Tyrosine kinase associated receptors :
Work the same way as the first type just that they don’t have intrinsic enzyme activity but are associated with cytoplasmic tyrosine kinase.
When the ligand bind on the receptors, the cytoplasmic kinases phosphorylate target proteins to relay the signal OR Tyrosine Kinase-Associated Receptors (TKAR):
• These receptors do not have enzyme activity themselves — they can’t add phosphate groups on their own.
• Instead, they are linked to separate tyrosine kinase proteins inside the cell (in the cytoplasm).
• When a ligand binds to the receptor on the outside, it causes a change that activates the associated cytoplasmic tyrosine kinase.
• The activated kinase then phosphorylates other proteins inside the cell to pass on the signal
- Receptor serine threonine kinases :
Have serine threonine kinase domain on their intracellular end.
There are two classes of this type. Type I and type II.
Ligand binding brings the two types together so that the type II receptor can phosphorylate and activate the type I receptor which in turn recruits and phosphorylates target proteins to relay the signal
Apparently there’s a fourth type that is like a class on its own but can be a type of enzyme coupled receptor :
4. Membrane bound guanylate cyclase receptors.
Ah, got it! You meant Protein Kinase G (PKG) — not G proteins.
Here’s how that fits in:
cGMP and Protein Kinase G (PKG)
• When guanylate cyclase produces cGMP, the cGMP acts as a second messenger inside the cell.
• One major target of cGMP is Protein Kinase G (PKG).
• PKG is a kinase enzyme activated by cGMP.
• Once activated, PKG phosphorylates specific proteins in the cell to cause effects like muscle relaxation, changes in ion channel activity, or gene expression changes.
Summary of the pathway:
1. Ligand binds to membrane guanylate cyclase receptor or NO activates soluble guanylate cyclase.
2. Guanylate cyclase produces cGMP from GTP.
3. cGMP activates Protein Kinase G (PKG).
4. PKG phosphorylates target proteins → leads to physiological responses (e.g., vasodilation).
So:
• cGMP activates PKG — not G proteins.
• PKG is the main effector kinase for cGMP signaling.
If you want, I can help explain what PKG phosphorylates and how that leads to specific effects!
What is cGMP?
• cGMP (cyclic guanosine monophosphate) is a second messenger inside cells.
• It helps relay signals from outside the cell to inside, controlling things like blood vessel relaxation, vision, and cell growth.
What is Guanylate Cyclase?
• Guanylate cyclase is the enzyme that makes cGMP from GTP (guanosine triphosphate).
• There are two types:
1. Membrane-bound guanylate cyclase receptors:
• These are transmembrane receptors.
• They have an extracellular part that binds ligands (signals) like atrial natriuretic peptide (ANP).
• When ligand binds, the enzyme part inside the cell turns GTP into cGMP.
• This increases cGMP inside the cell, triggering downstream effects like lowering blood pressure.
2. Soluble guanylate cyclase:
• This is found inside the cell (cytoplasm).
• It’s activated by nitric oxide (NO), a gas made in response to some signals.
• When NO binds soluble guanylate cyclase, it produces cGMP, which then acts as a second messenger.
Summary
Type Location Activator Function
Membrane-bound guanylate cyclase In the plasma membrane Ligands like ANP Makes cGMP to signal inside the cell
Soluble guanylate cyclase Inside the cytoplasm Nitric oxide (NO) Makes cGMP for various signaling pathways
Why is cGMP important?
• It relaxes smooth muscles (like in blood vessels) causing vasodilation.
• It helps in vision by working in photoreceptor cells.
• It regulates other cell functions depending on the tissue.
If you want, I can explain the signaling pathways involving cGMP in more detail!
Ion channels transmembrane receptors are usually closed but open up when specific ligands bind to them. When they open up, they allow ions to passively flow into the cell and this causes a shift in electrical charge distribution in the cell causing a cellular response.
What are autocrine signals?
Paracrine?
Endocrine?
Give examples for each
Why do we need transmembrane proteins?
Autocrine signals or
Molecules target the same cells
Paracrine target nearby cells:
Endocrine target distant cells: has Ligands-Often small and stable, with high affinity for their receptors due to their dilution in the blood.
Juxtacrine: Definition: Requires direct physical contact between cells. The signaling molecule is membrane-bound, not secreted.
Receptors: Found on adjacent cells, but not across tight junctions.
Examples of signaling types:
1. Autocrine signaling:
• Cancer cells releasing growth factors that stimulate themselves
• T cells producing interleukin-2 (IL-2) to stimulate their own proliferation
• Platelets releasing thromboxane A2 to activate themselves during clotting
2. Paracrine signaling:
• Neurotransmitters like acetylcholine acting on nearby muscle cells
• Histamine release during inflammation affecting nearby blood vessels
• Growth factors like fibroblast growth factor (FGF) affecting nearby cells in tissue repair
3. Endocrine signaling:
• Insulin released by the pancreas traveling through the blood to muscle and fat cells
• Thyroid hormones (T3 and T4) regulating metabolism in distant tissues
• Cortisol released by adrenal glands affecting many organs
We need them because:
Hydrophobic ligands diffuse across the cell membrane and bind to receptor proteins inside the target cells.
Hydrophilic ligands can’t do this or can’t enter the cells so they bind to transmembrane receptors which have an intracellular end inside the cell that triggers a signaling pathway inside the target cell.
State two examples of hydrophobic ligands and two of hydrophilic ligands
Hydrophobic: Here are some common examples of hydrophobic ligands:
• Steroid hormones like cortisol, estrogen, testosterone, aldosterone
• Thyroid hormones like T3 (triiodothyronine) and T4 (thyroxine)
• Vitamin D (calcitriol)
• Retinoids (vitamin A derivatives)
Hydrophilic:
Peptide hormones like insulin, glucagon, and growth hormone
• Catecholamines like epinephrine (adrenaline) and norepinephrine
• Neurotransmitters like acetylcholine and serotonin
• Growth factors like Epidermal Growth Factor (EGF) and Platelet-Derived Growth Factor (PDGF)
• Cytokines such as interleukins and interferons
What is cellular communication?
What is signal transduction?
Cellular communication is How cells interact/respond to stimulus
Examples of stimulus:
Light, pH, temperature, pressure
–Sound
–Aroma/smell
–Concentration of a particular Molecule
–Ie—detects the need for action
When there is Conversion of information to chemical change = signal transduction
Or Signal transduction is the process where a cell receives a signal (like a hormone) and changes it into a specific chemical response inside the cell for an action to occur.
State the 7 steps in cell communication
-Involves synthesis.
-Release of the signaling molecule by the signaling cell.
-Transport of the signal to the target cell.
-Binding of the signal by a specific receptor protein leading to its activation.
-Initiation of one or more intracellular signal-transduction pathways by the activated receptor.
-Specific changes in cellular function, metabolism, or development.
-Removal of the signal.
Or
general overview of how signal transduction works. Here’s a simplified version of the general principles of signal transduction using the terms you’re seeing:
General Principles of Signal Transduction
1. Signal Recognition
– A ligand (e.g., hormone or neurotransmitter) is released and binds to a specific receptor on the target cell.
2. Signal Generation
– Binding activates intracellular signaling pathways, often involving second messengers (like cAMP, Ca²⁺) or enzymes (like kinases).
3. Signal Amplification and Relay
– One signal can trigger a cascade of reactions, amplifying the message and passing it through different molecules inside the cell.
4. Cellular Effect
– The final signal causes a specific cellular response, such as:
• Gene expression changes
• Enzyme activation
• Secretion
• Cell division or movement
5. Signal Termination
– The signal is turned off when no longer needed to keep the system balanced.
Would you like a diagram-style summary or a one-line version for memorization?
Four features of signals
Name them
- Specificity – Each signal (ligand) binds only to its specific receptor.
- Amplification – A small amount of signal can trigger a large cellular response.
- Desensitization/Adaptation – The cell can reduce its response if the signal is constant.
- Integration – The cell can combine multiple signals to produce a coordinated response.
State the classification of receptors based on their cellular location
How do they work?
1.Plasma membrane – (hydrophilic, involves 2nd messengers)
2.Cytoplasmic
3.Nuclear
plasma membrane/extracellular receptors
Interact with molecules or signals or ligands that
–Are water soluble (hydrophilic)
–Have no transport protein – short half-life
–Initiate response by binding to plasma membrane receptors
–Require 2nd messengers to generate signals to effect appropriate response
–Eg. peptide and catecholamine hormones
intracellular/cytoplasmic, nuclear
–Lipophilic signals or ligands or molecules interact with these type of receptors
–Diffuse across plasma membrane
–Binds specific receptor(s) in the cytoplasm or the nucleus
–Ligand-receptor binding results in conformational modification and activation or The receptor-ligand complex then often moves into the nucleus if it started in the cytoplasm.In the nucleus, it changes gene expression.
–Movement of activated receptor to appropriate site for required cellular response(
Hydrophobic signals cross the cell membrane, bind to receptors inside the cell, and the activated receptor-hormone complex moves to the nucleus to control gene activity and produce the cellular response.)
Hydrophobic ligands enter the cell and bind cytoplasmic or nuclear receptors.
•
State the general properties of receptors
-Specific :bind single/closely related molecules. Each receptor only binds to one particular molecule or very similar ones—like a lock and key
-Receptor-ligand complex is also specific for effector. When the receptor and molecule (ligand) join, they form a complex that only works with a specific partner inside the cell to cause a response.
–Maximal cellular response can be induced without activation/binding of all receptors. You don’t need to activate all the receptors to get the strongest possible response—just some of them
–Sensitivity dependent on number of receptors. How sensitive a cell is to a signal depends on how many receptors it has.
–Detected/identified by specific assays (binding , competitive assays). Scientists can detect these receptors using special tests that show how well molecules bind to them.
–Can be purified by affinity techniques or expressed from cloned genes. Receptors can be isolated and studied by using their ability to specifically bind certain molecules or by making them from cloned genes.
Explain affinity labeling under affinity techniques where you use special tests to show how well molecules bind to certain feceptors
Affinity Labeling (Expanded Explanation):
It’s a binding-based technique used to identify and isolate receptors by using a specially designed radiolabeled ligand (a ligand with a radioactive tag) that binds to the receptor.
Step-by-step from your notes:
1. Mix cells with excess radiolabeled ligand
– The ligand is designed to specifically bind the receptor of interest.
2. Wash to remove unbound ligand
– Only ligand attached to receptors stays behind.
3. Add a cross-linker
– This causes the ligand to form a covalent bond with the receptor. It “locks” the ligand in place on the receptor.
Even though the ligand binds to the receptor as said in point 2, the bond is weak and reversible. Cross-linking forms a strong covalent bond to permanently attach the ligand to the receptor so it won’t wash off during experiments.
4. Result:
– Now, even if you treat the sample with harsh chemicals (detergents, heat, etc.), the ligand-receptor complex stays intact, allowing you to detect or purify the receptor.
In short:
Affinity labeling uses a radiolabeled ligand and a chemical cross-linker to irreversibly tag receptors, making them easy to detect or isolate even in rough conditions.
Explain affinity chromatography
Here’s a simple summary of that affinity chromatography technique:
Affinity Chromatography (Receptor Isolation Method):
• Beads in a column are coated with a ligand that specifically binds the receptor you’re looking for.
• You pass a mixture of membrane proteins (from cells) through the column.
• Only the receptor binds to the ligand on the beads — the rest passes through.
• Then you add free ligand in excess to compete and knock off the receptor from the beads.
• The receptor comes out purified and still able to bind its ligand.
Key Point:
This method isolates just the receptor based on its specific binding to its ligand — and the receptor still works after purification.
The receptor is still working after it’s knocked off because:
• The binding between the receptor and the ligand on the beads is non-covalent (reversible), just like how it naturally works in the body.
• When you wash the column with free ligand, it competes with the bead-bound ligand and replaces it, gently pulling the receptor off without damaging it.
So:
• You’re not breaking the receptor.
• You’re just freeing it from the column using its natural ligand.
• Because no harsh chemicals or denaturation is used, the receptor stays functional and can still bind ligands later.
Explain functional assay method receptor identification
Great! Let’s break down the functional assay method for receptor identification in simple terms:
What is a Functional Assay?
A functional assay identifies receptors based on the biological response they trigger when a ligand binds — rather than just detecting their physical presence.
How it works (step-by-step):
1. Introduce a ligand (known or suspected to bind a receptor) to cells or tissues.
2. Observe the response — like:
• Increased enzyme activity
• Production of a second messenger (e.g., cAMP, IP3)
• Change in gene expression
• Altered ion flow, cell shape, proliferation, etc.
3. If a specific response is seen, you can conclude that:
• The receptor is present
• It is functional and capable of triggering a signaling pathway.
Why it’s useful:
• It helps confirm not just that the receptor exists — but that it’s actually doing its job.
• It’s helpful when you don’t know the exact structure or sequence of the receptor but know the effect it should cause.
Example:
If adding adrenaline to cells increases heart rate or cAMP levels, you know that beta-adrenergic receptors (which respond to adrenaline) are present and functional.
Let me know if you’d like to compare this with other receptor identification methods (e.g., affinity labeling, chromatography)!
State three differences between the three types of affinity techniques
Feature / Method
A.Affinity Labeling
B.Affinity Chromatography
C. Functional Assay
- Purpose
A.Identify and permanently tag receptor
B.Purify receptor based on specific ligand binding
C. Detect functional receptor activity via cellular response
2.Ligand-Receptor Interaction A.Covalent (permanent, via cross-linking)
B.Non-covalent (reversible) C.Natural, non-covalent interaction triggering response
3.Process Summary A.Radiolabeled ligand binds receptor, then cross-linker is added to form a covalent bond
B.Ligand is attached to beads; receptor binds and is later eluted
C.Ligand is added to cells; response (e.g. cAMP, gene expression) is measured
4.Output
A. Receptor-ligand complex that is stably labeled for detection B.Purified receptor that still functions
C. Confirmation that receptor works and causes a biological effect
5.Used For
A. Studying receptor structure, labeling, identification
B. Isolating receptor proteins for study or reuse
C. Verifying receptor activity and presence in a living system
- Example Tool
A.Radiolabeled ligand + cross-linker
B.Ligand-bound beads + elution buffer
C. Measurement of second messengers (e.g. cAMP assay, calcium imaging) - Type of Data
A. Molecular identity (via radioactivity or gel)
B. Physical purification (protein bands)
C.Functional data (e.g., enzyme activation, ion flux, signal cascade)
Complexity/Harshness Moderate; irreversible step with cross-linker Gentle; reversible binding Simple or complex, depending on response being measured
Summary:
• Affinity labeling: Best for locking and detecting a specific receptor.
• Affinity chromatography: Best for purifying receptors.
• Functional assay: Best for checking if a receptor is active and doing its job.
State four examples of secondary messengers
INTRACELLULAR SIGNAL TRANSDUCTION
•the Information contained in signaling molecules is transduced to other forms to alter cellular biochemistry.
It’s the process by which a signal (usually from outside the cell) is converted into a series of internal changes that lead to a specific cellular response.
Think of it as a domino effect inside the cell — where the signal is passed on and amplified by molecules called second messengers.
–2nd messengers
–Calcium ion
–Cyclic AMP
–Cyclic GMP
–Inositol 1,4,5-triphosphate (IP3)
–Diacylglycerol (DAG)
Protein kinase C in DAG
Protein kinase A in cAMp
Protein kinase G in cGMP
Importance of secondary messengers
What is crosstalk.
ADVANTAGES
•Free to diffuse to other cellular components
•May amplify the signal
•Single messenger in several signaling pathways
–Promotes crosstalk
Here’s a simple explanation of those advantages of second messengers like cGMP or cAMP:
• Free to diffuse: They can move easily inside the cell to reach different targets, spreading the signal quickly.
• Signal amplification: One activated receptor can produce many second messenger molecules, making the signal stronger and faster.
• Single messenger in multiple pathways: The same second messenger can be used by different signals, allowing communication between pathways (called crosstalk), which helps the cell coordinate complex responses.
Want me to explain this with an example?
Explain how these proteins in signal transduction help regulate it :
Guanine nucleotide-exchange factor (GEF)
GTpase
Kinases
Phosphatases
Here’s a simple breakdown of those proteins involved in signal transduction:
• Guanine nucleotide-exchange factor (GEF): Helps activate G proteins by swapping GDP for GTP, turning the G protein “on.”
• GTPase activating protein (GAP): Speeds up the G protein’s GTP to GDP hydrolysis, turning the G protein “off.”
• Kinases: Enzymes that add phosphate groups (phosphorylation) to proteins, often activating or changing their function.
• Phosphatases: Enzymes that remove phosphate groups (dephosphorylation), often turning proteins off or resetting them.
Together, these proteins control the activation and deactivation of signals inside the cell to make sure the message is passed accurately and stopped when needed.
Explain how epinephrine and cholera toxin works in signal transduction
Epinephrine (Adrenaline) Action
• Epinephrine binds to G protein-coupled receptors (GPCRs) on target cells.
• This activates the Gs protein, which activates adenylyl cyclase.
• Adenylyl cyclase converts ATP to cAMP (a second messenger).
• cAMP activates protein kinase A (PKA).
• PKA phosphorylates target proteins to produce effects like increased heart rate, glycogen breakdown (energy release), etc. Or Phosphorylation of cellular proteins by PKA causes the cellular response to epinephrine.
Cholera Toxin Action
• Cholera toxin modifies the Gs alpha subunit of the G protein.
• It locks Gs in its active form by preventing GTP hydrolysis (can’t turn off).
• This causes continuous activation of adenylyl cyclase → lots of cAMP.
• High cAMP causes excessive secretion of water and ions in intestinal cells → severe diarrhea.
Great question! Here’s why high cAMP causes excessive water loss, like in cholera:
1. In intestinal cells, there are chloride (Cl⁻) channels controlled by cAMP (specifically the CFTR channel).
2. When cAMP levels rise too much, these Cl⁻ channels stay open continuously.
3. Chloride ions flood into the intestinal lumen (the gut).
4. Sodium (Na⁺) follows chloride to balance the charge.
5. Water follows salt by osmosis into the gut lumen.
6. This leads to massive water secretion into the intestines, causing diarrhea and dehydration.
So, high cAMP keeps ion channels open too long, pulling water out of the body into the intestines.
How is cAMP signal degraded
Exactly! Here’s how cAMP degradation works:
• After cAMP carries the signal inside the cell, it needs to be turned off to stop the signal.
• This is done by an enzyme called cyclic nucleotide phosphodiesterase (PDE).
• PDE breaks down cAMP into AMP (adenosine monophosphate), which is inactive.
• By degrading cAMP, PDE helps reset the signaling pathway so the cell can respond properly to new signals.
So, phosphodiesterases control the intensity and duration of cAMP signaling by breaking down cAMP. The same goes for cGMP—they have specific PDEs to degrade it too.
Want me to explain how PDE inhibitors (like some drugs) affect this process?
State the types of secondary messengers (cyclic nucleotides, calcium ions, Inositol 1,4,5-triphosphate (IP3) , Diacylglycerol (DAG) ) and how they’re segraded
- Cyclic Nucleotides
• cAMP (cyclic adenosine monophosphate)
• Produced by: Adenylyl cyclase
• Degraded by: Phosphodiesterase (PDE) enzymes, which convert cAMP → AMP (inactive)
• cGMP (cyclic guanosine monophosphate)
• Produced by: Guanylyl cyclase
• Degraded by: Phosphodiesterase (PDE) enzymes, which convert cGMP → GMP (inactive) - Calcium ions (Ca²⁺)
• Released from intracellular stores or through channels.
• Removed by:
• Calcium pumps (ATP-driven) that move Ca²⁺ back into the endoplasmic reticulum or out of the cell.
• Calcium-binding proteins that buffer free Ca²⁺ levels. - Inositol 1,4,5-triphosphate (IP3)
• Produced by: Phospholipase C (PLC) acting on PIP2
• Function: Releases Ca²⁺ from intracellular stores.
• Degraded by:
• Dephosphorylation by specific phosphatases into inactive forms. - Diacylglycerol (DAG)
• Produced alongside IP3 by PLC.
• Functions by activating Protein Kinase C (PKC).
• Degraded by:
• Conversion into phosphatidic acid via DAG kinase.
• Further metabolism by lipases.
Examples of enzymes affected by calcium
EXAMPLES OF EZYMES
AFFECTED BY Ca2+
Adenylyl cyclase
Ca?+-dependent protein kinases
Ca?+-Mg?+ ATPase
Ca?+-phospholipid-dependent protein kinase
Cyclic nucleotide phosphodiesterase
Some cytoskeletal proteins
Some ion channels (eg, L-type calcium channels)
Nitric oxide synthase
Phosphorylase kinase
Phosphoprotein phosphatase 2B
Some receptors (eg, NMDA-type glutamate receptor)
