Quiz #1 (9/30-10/5)

Question 1

Pharmacology

Answer 1

The science concerned with studying the action of chemicals/drugs in biological systems

Question 2

Pharmacodynamics

Answer 2

effect of drugs on the body. Involves the relationship of the drug concentration at the site of action over time and the mechanism of action and magnitude of effect. Defined by Receptor binding, Signaling mechanism, Agonist & Antagonist, Dose-response curve and Physiological effect.

Question 3

Pharmacokinetics

Answer 3

effect of the body on drugs. Involves the relationship of the drug dose and the drug concentration at the site of action over time. Defined by ADME

Question 4

Drug and it’s MW

Answer 4

any substance by virtue of its chemical properties, that brings about a change in a biological system. Or more practically, any substance approved by the FDA for the treatment or prevention of disease. Include inorganic ions, small peptides, proteins, nucleic acids, lipids, carbohydrates, etc…

Large range of molecular weight (100-1000). If the drug is too small it may have insufficient selectivity for target sites, but if it is too large it may have poor absorption and distribution in the body.

Question 5

Receptors

Answer 5

specific molecules that drugs interact with to bring about a functional change in a biological system. Only receptors with selective drug-binding properties are of clinical value. Most are altered or modified when bound by a drug molecule and binding of the drug initiates a signaling mechanism that leads to the observed effect

Question 6

Acetylcholine receptor

Answer 6

located at the neuromuscular junction. Contains 5 subunits of which ACh binds to two alpha-subunits stimulating a small conformation change that opens a channel allowing the influx of Na+ and thus muscle contraction.

Question 7

Receptor Types

Answer 7

1. Proteins: most common. Bind hormones or neurotransmitters, are ion channels and/or transport proteins, or enzymes.
2. Nucleic Acid: DNA (target of many anticancer drugs) and RNA

3 Membrane lipids

4. “Nonreceptor” drugs are drugs that don’t bind a receptor but still have an effect on the body. Examples include antacids which chemically neutralize stomach acid or the class of osmotic diuretics which directly increase osmolarity of the nephron which draws water from the blood to the lumen.

Question 8

Receptor Signaling Methods

Answer 8

1. nuclear receptors: include steroid hormones, estrogen, thyroid hormone and vitamin D. These are intracellular receptors so the drug has to be able to cross the cellular membrane in order to bind to the target
2. Kinase-linked receptors: include growth factors and cytokines. Tyrosine kinase or JAK-STAT are the two kinase linked receptor classes
3. Ion channels: include acetylcholine and glutamate. The receptor and effector are on the same molecule
4. GPCRs: include histamines, opioids and serotonin.

Question 9

Effectors

Answer 9

molecules that translate the drug-binding event into a change in cellular activity.

most often are enzymes. Examples are protein kinase, adenylyl cyclase, phosphodiesterase, phospholipase.

Can be part of the receptor. Examples: insulin receptor contains a tyrosine kinase and the nicotinic acetylcholine receptor is an ion channel that functions as the effector.

Question 10

Drug-Receptor Interactions

Answer 10

Properties: multiple sites of interaction between the drug and the receptor, short range of interactions, specific interactions between chemical groups on drug and receptor

At least 3 points of contact are required between the drug and receptor to maintain stereochemistry/see a difference in isomer activity.

Question 11

Communication via circulating hormones

Answer 11

hormones or neurotransmitters are produced from hormone-producing cells as precursors and are then processed and stored for secretion.

Secretion and degradation of hormones is regulated

Hormone/neurotransmitter then binds to a receptor on the target tissue mediating a biochemical and physiological change in the target cell. Cell surface receptors are “pharmacological windows of opportunities” because we can use them to regulate specific types of cellular physiology.

Question 12

General receptor couplings

Answer 12

1. two messenger system
2. ion channel coupled receptor
3. steroid hormone receptors
4. receptor kinase/phosphotase or other enzymatic activity

Question 13

Ion channel coupled receptor

Answer 13

fast response rate. The receptor can be coupled to an ion channel or can be an ion channel, and activation of the receptor leads to changes in ion flux across the membrane. Example is the nicotinic acetylcholine receptor at the neuromuscular junction (ligand-gated).

Question 14

Steroid hormone receptors

Answer 14

hormone must cross the cell membrane to interact with an intracellular receptor to regulate gene transcription through interaction with a specific response element in the promoter of the gene.

Question 15

Receptor kinase/phosphatase or other enzymatic activity receptor

Answer 15

Example is signaling through the MAP kinases which can include hormones, which affect proliferation, differentiation and survival of cells.

Question 16

General mechanism of two messenger systems

Answer 16

an extracellular messenger (hormone or neurotransmitter) interacts with a cell-surface receptor to influence the function of the cell without actually entering the cell. The actions of the primary messenger are mediated through the second messenger whose concentration varies (increase or decrease) in response to receptor activation.

Question 17

Regulatory advantages of two messenger systems

Answer 17

1. A primary messenger can influence the cell from outside without entering the cell. (Expands the chemistry of the receptor agonist/antagonist to include charged molecules.)
2. Intracellular second messengers are generally small molecules and diffuse rapidly to target molecules. They are rapidly synthesized and degraded resulting in fast response times and signal termination. cAMP is an example
3. The primary signal can be amplified. Example is through downstream kinase cascades.
4. There can be multiple inputs into a common secondary messenger.
5. The complexity of the system generates many control points, allowing cross-talk between different signal transduction systems

Question 18

Common second messengers

Answer 18

1. cAMP: first second messenger described. Role in autonomic, CNS and endocrine.
2. cGMP: important for vision and smooth muscle contraction
3. Calcium: universal second messenger (prokaryotic and eukaryotic cells) important in autonomic and CNS.
4. Phosphoinositide breakdown products, including IP3 and DAG
5. Arachidonic acid derived from lipids
6. NO (nitric oxide) which can diffuse across cellular membranes and effect neighboring cells.

Question 19

cAMP structure

Answer 19

small neucleotide synthesized from ATP, Mg 2+ is a cofactor and adenylyl cyclase catalyzes the reaction
discovered because it stimulated glycogen breakdown in liver and skeletal muscle (through adrenaline as a first messenger)

Question 20

Physiological processes controlled by cAMP (11)

Answer 20

1. stimulates glycogenolysis (breakdown of glycogen), inhibits glyconeogenesis (synthesis of glycogen), stimulates lipolysis (breakdown of triglycerides
2. release of hormones and neurotransmitters: in general increases in presynaptic cAMP 3. enhances neurotransmitter release.
3. muscle contractility: stimulates heart muscle through primary messenger of adrenaline. smooth muscle
4. steroidogenesis
5. ion channel function: example is AMPA glutamate receptors which is cAMP-dependent protein kinase regulated
6. cell proliferation: cAMP generally is anti-proliferative for most animal cells.
7. cellular differentiation: for cells to differentiate they must stop dividing. Because cAMP is anti-proliferative it stimulates differentiation.
8. gene transcription: through CRE (cAMP response element) which is a sequence found in the promoters of some genes that allows cAMP to increase transcription of specific genes.
9. memory formation: especially in long-term memory which is completely dependent on cAMP
10. melatonin synthesis in the pineal: from serotonin which is regulated by cAMP
    neurotransmitter release

Question 21

Synthesis and degradation of cAMP

Answer 21

ATP –> cAMP catalyzed through adenylate cyclase and releases a PPi

cAMP –> 5’-AMP hydrolysis through cAMP phosphodiesterase.

cGMP is synthesized from GTP catalyzed by guanylyl cyclases and breakdown through hydrolysis by cGMP phosphodiesterase

Question 22

changes in concentrations of cAMP

Answer 22

local and transient. Prolonged increases in cAMP are toxic. The shape and duration of the transients encode specific information.

olfactory sensory neurons: generates cAMP oscillations which may encode specific information used by animals for olfactory responses

need mechanisms to rapidly reduce second messenger concentrations

Question 23

xanthines and methylxanthines

Answer 23

include Xanthine, Theobromine, caffeine, theophylline.

Increase cAMP in brain through inhibition of PDE’s to increase cognition and long-term memory

Also stimulate a class of adenosine receptors that are coupled to stimulation of adenylyl cyclase, therefore there are two mechanisms by which they increase cAMP

Question 24

Viagra

Answer 24

initially developed as a cardiovascular drug for hypertension
inhibits PDE 5 which prevents breakdown of cGMP.
cGMP then acts to cause vascular smooth muscle relaxation, increased blood flow to the penis and penile erection

Question 25

cAMP signal transduction system

Answer 25

1. agonist binds to either a stimulant or inhibiting receptor located in the plasma membrane. Agonists can include peptide hormones, catacholamines, muscarinic agonists and neurotransmitters.
2. binding to the receptor activates adenylate cyclase to form cAMP
3. cAMP activates cAMP-dependent protein kinase which catalyzes phosphorylation of specific proteins, generally this is PKA

Question 26

PKA

Answer 26

1. some protein kinases: cAMP-dependent/PKA, cGMP-dependent/PKG, receptor tyrosine kinases and the Calcium-activated: myosin light chain kinases in smooth muscle and skeletal muscle, phosphorylase kinase (also regulated by cAMP), calmodulin-dependent kinases, protein kinase C (PKC)regulated by DAG and Ca
2. PKA contains two regulatory subunits and two catalytic subunits.
3. Binds four cAMP molecules to release the two active catalytic subunits
4. PKA phosphorylates its substrates and changes their activity.

Question 27

regulation of cAMP signal transduction system

Answer 27

phosphatases: catalyze the dephosphorylation of protein substrates reversing the actions of PKA. These phosphatases are regulated
agonists: decreasing levels of agonists decreases system
PDE: decreases level of the second messenger, cAMP

Question 28

cAMP in glycogenolysis stimulation and glycogen synthesis inhibition

Answer 28

1. primary messenger is epinephrine or glucagon which acts to form cAMP.
2. cAMP activates the conversion from inactive protein kinase to active protein kinase
   active protein kinase has two main activities
   with the addition of ATP it catalyzes the reaction of active glycogen synthase to inactive glycogen synthase
3. with the addition of ATP it catalyzes the reaction of inactive phosphorylase kinase to active
4. active phosphorylase kinase with the addition of ATP catalyzes inactive phosphorylase b to the active form which catalyzes breakdown of glycogen to glucose
5. Pros: cascade leads to rapid amplification of the signal to generate glucose during the “fight or flight”

Question 29

cAMP and lipolysis

Answer 29

1. primary messenger are hormones and/or catecholamines to stimulate adenylyl cyclase in fat cells to produce cAMP
2. cAMP activates PKA which phosphorylates and activates the enzyme lipase.
   lipase catalyzes the breakdown of triglycerides to free fatty acids and glycerol.
3. methyl xanthenes including caffeine can stimulate lipolysis by inhibiting PDEs and activating AC.
4. Beta-adrenergic antagonists (propranolol) block adrenaline activation of fat adenylyl cyclase but not activation by peptide hormones like glucagon.

Question 30

Leptin sensitivity

Answer 30

1. genetic linkage between type 3 adenylyl cyclase and obesity. Gene is AC3 which is the type 3 adenylyl cyclase. Knockout mice for AC3 are obese, and obesity seems to be due to leptin insensitivity
2. Normal Mechanism: when you start becoming fat, white adipose begins secreting the hormone leptin which interacts with receptors in the hypothalamus to form alpha-MSH. Alpha-MSH interacts with MC4R stimulating AC3 to produce cAMP. cAMP eventually leads to suppressed appetite and decreased food consumption.
3. When AC3 is defective leptin signaling does not produce cAMP and appetite suppression and decreased food intake does not occur.

Question 31

cAMP and NT

Answer 31

some neurotransmitter receptors regulate cAMP. Examples include beta and alpha adrenergic receptors, dopamine, serotonin, muscarinic and histamine

cAMP produced has several neuromodulatory effects including ion channel activity (through PKA), increases in neurotransmitter release and increases in transcription

Question 32

cAMP and the heart contraction cycle

Answer 32

catecholamines such as epinephrine and norepinephrine bind to beta-adrenergic receptors in the myocardium that are coupled to AC activation.

heart rate shows a cyclical oscillation of cAP that parallels the contraction cycle. May be that cAMP controls a role in regulation of the cycle

Question 33

cAMP and olfaction

Answer 33

odorant binds to some receptor in the olfactory epithelium that is coupled to stimulation of AC3.

activation of AC increases cAMP levels which act to open cation ion channels specific for Sodium.

Process is also run with cGMP

Question 34

cAMP and transcription

Answer 34

1. intracellular cAMP activates PKA which phosphorylates CREB (CRE binding protein) which is a transcription factor
2. phosphorylation of CREB activates the transcription factor, which can now interact with the CRE DNA sequence (cAMP response element) to stimulate transcription of specific genes.
3. CREB transcription is required for memory formation

Question 35

cAMP and human disease

Answer 35

dysfunction of cAMP signal transduction systems cause the following diseases
some tumors, including specific types of pituitary tumors

Question 36

cAMP and psoriasis

Answer 36

psoriasis which is characterized by rapid proliferation of skin due to abnormal cAMP levels. cAMP is anti-proliferative

Question 37

cAMP and pseudohypoparathyroidism

Answer 37

genetic endocrine disease, due to a defect in hormone coupling mechanisms which impairs the ability to couple receptors to AC

Question 38

cAMP and bacterial toxins

Answer 38

including E. coli strains, Anthrax, Pertussis make toxins that increase cAMP levels
depression, evidence

Question 39

cAMP and Grave’s Disease

Answer 39

1. Autoimmune disease in which the patient makes antibodies that activate the TSH receptor in the thyroid. The TSH receptor is coupled to AC and produces cAMP stimulating the release of thyroid hormone
2. Increased thyroid hormone causes increased thyroid cell growth (goiter formation).
3. antibodies recognize many different regions on extracellular surface receptor

Question 40

Intracellular free calcium

Answer 40

1. intracellular calcium controls secretion, metabolism, muscle contraction, cell shape, growth, proliferation, cell survival, synaptic plasticity in the CNS and transcription
2. In unstimulated cells [Ca2+] is 0.1 uM and outside cells is 1000 uM.
3. Increases in intracellular calcium are transient and prolonged increases can be toxic

Question 41

Mechanisms to increase intracellular Ca

Answer 41

1. Can either be voltage-sensitive (neurons and heart) or
2. NMDA glutamate activated which are ligand and voltage gated where the ligand is glutamate.
3. Phospholipase C coupled receptors: causes release of Ca2+ into the cell from the endoplasmic reticulum. Agonists bind the receptor and activate PLC. PLC catalyzes the formation of IP3 and diacylglycerol from PIP2. IP3 binds to an IP3 receptor in the ER to release Ca into the cytoplasm.

Question 42

Intracellular calcium actions

Answer 42

Calcium can act to regulate PKC or calmodulin. Calmodulin regulates enzymes and non-enzymatic proteins. Calmodulin has 4 calcium binding sites and when calcium binds to calmodulin it has enhanced affinity for its target protein through exposure of a hydrophobic domain on calmodulin.

Question 43

PLA2/arachidonic acid pathway

Answer 43

1. agonists stimulate receptors that can be subclasses of serotonin and dopamine.
2. activation of the receptor activates phospholipase A2 through GPCR
   PLA2 leads to the formation of the second messenger, arachidonic acid.
3. AA is a precursor for many compounds including prostaglandins1

Question 44

general properties of AC

Answer 44

1. catalyzes the formation of cAMP from ATP. Is generally saturated with substrate (ATP) and is controlled by regulation of its turnover number.
2. Each adenylyl cyclase is unique in regulatory properties and tissue and subcellular distribution
3. Structure: AC contains 12 transmembrane spanning domains (anchoring, voltage sensitivity? or maybe ion channels?) with two large cytoplasmic loops (catalytic subunits)
4. Multiple receptors can couple to a single catalytic subunit of an AC
5. Receptor subunits and catalytic subunits are separate proteins on an AC and are encoded by distinct genes.

Question 45

Regulatory mechanisms of AC (8)

Answer 45

1. Calcium stimulation mediated through calmodulin. Examples are AC1 and AC8. Required for memory consolidation
2. Calcium inhibition of AC3 mediated through CaM kinase II phosphorylation of AC3. Detection of odor.
3. Stimulation by Gs-coupled receptors. Example is beta-adrenergic receptors in the heart and respiratory smooth muscle
4. Inhibition by Gi-coupled receptors. Example is muscarinic receptors and alpha-2 adrenergic receptors
5. Stimulation or inhibition by the beta/gamma complex of G-coupling proteins. Examples are AC2 and AC4 (both are stimulated)
6. Stimulation by protein kinase C.
7. Inhibition by PKA. example is AC5. example of feedback inhibition because as cAMP increases it activates PKA which in turn feedback inhibits the AC
8. Hormone regulation is through tissue specificity. ACs in different tissues are coupled to different receptors. Example is in the heart beta-adrenergic and glucagon receptors are coupled to stimulation of AC whereas muscarine receptors are coupled to inhibition of AC.

Question 46

agonist dose response curves

Answer 46

1. example with glucagon and AC activity. binding of agonists (glucagon) to their receptors correlates quantitatively with stimulation of AC
2. Example with beta-adrenergic agonist: interactions of agonist with their receptors are very specific and have high affinity. May vary between isoforms of a drug.
3. Binding of the drug is necessary but not sufficient for receptor stimulation of ACs. An example is that beta-adrenergic antagonists bind to beta-adrenergic receptors with high affinity but do not stimulate the enzyme

Question 47

stimulation of AC by Gs

Answer 47

Stimulation of AC by Gs-coupled or Gi-coupled receptors requires three proteins: receptor (Rs or Ri), guanylyl nucleotide coupling protein (Gs or Gi) and the catalytic subunit of AC (C)

Question 48

Activation of Gs or Gi

Answer 48

both are activated with GTP is bound to them. and both have intrinsic GTPase activity which catalyzes the formation of GTP to GDP making the protein inactive. Effectively, HR (hormone receptor complexes) are guanylyl nucleotide exchange factors (GEF) because the catalyze the exchange of GTP for GDP bound to G coupling proteins. When Gs is activated it stimulates AC and when Gi is activated it inhibits AC.

Question 49

structure of Gs or Gi

Answer 49

heterotrimeric G proteins with 3 subunits: alpha, beta and gamma. Beta and gamma subunits function as a complex. Gs-alpha and Gi-alpha are the subunits that bind GTP and have intrinsic GTPase activity. The beta/gamma complex inhibits the activity of either Gs-alpha or Gi-alpha.

when Gs is activated it stimulates AC and the beta/gamma subunit that dissociated will inhibit the activity of the Gi subunit.

when Gi is activated it inhibits AC and the dissociated beta/gamma subunit inhibits the activity of the Gs subunit.

Question 50

Cholera toxin

Answer 50

cholera toxin catalyzes the ADP ribosylation of the Gs-alpha subunit which inactivates the GTPase activity. The result is overproduction of cAMP and associated diarrhea

Question 51

Pertussis toxin

Answer 51

the pertussis toxin invades animal cells and grow’s in the host’s lungs. It catalyzes the ADP-ribosylation of Gi thereby inhibiting its activity. Inhibition of Gi results in increased AC and cAMP. Bordetella pertussis also makes a small highly active adenylyl cyclase which invades human cells and increases cAMP

Question 52

anthrax toxin

Answer 52

the pathogen makes several toxins that invade animal cells including a soluble adenylyl cyclase called edema factor that invades cells and elevates cAMP levels.

Question 53

Vibrio vulnificus biotype 3 toxin

Answer 53

gram negative pathogen that causes severe food-borne and wound infections including tissue necrosis, septicemia, organ failure and death all within 48 hours of exposure. Creates an invasive adenylyl cyclase that raises levels of cAMP.

Question 54

Pseudohypoparathyroidism

Answer 54

rare endocrine disease that results in mental retardation, stunted growth and defects in the endocrine system

Patients are unresponsive to parathyroid hormone and other hormones that normally couple to AC stimulation, resulting in very low levels of cAMP in their urine (healthy individuals will show measurable levels).

Have a mutated Gs

Question 55

Pituitary and thyroid tumors

Answer 55

Mechanism: GHRH couples to its receptor activating Gs and thus AC to form cAMP. cAMP promotes the release of GH
In pituitary tumors, Gs is mutated to lower GTPase activity of Gs and cAMP levels are increased resulting in excessive release of GH. Excessive GH results in uncontrolled growth of the pituitary

Question 56

Transducer and cGMP

Answer 56

cGMP opens with sodium channels in rod cells to open them. When cGMP is lowered through PDE the sodium channels close resulting in hyperpolarization of rod cells and signaling.

Transducin also has intrinsic GTPase activity which shuts off the signal and a beta/gamma subunit which binds the alpha subunit and inhibits it when GDP is bound to the alpha subunit.

Primary signal is light, the receptor is rhodopsin, the G protein is transducin, the effector system is a cGMP phosphodiesterase and the second messenger is cGMP.