Lecture 2 Flashcards
PPT 1 and 2
What happens when a drug binds and gets stuck to a receptor?
A covalent bond is formed; becomes insurmountable
Drugs continuously bind and _____ to the receptor
Release
What does Duration of drug action refer to?
How long the drug will bind to the receptor
What happens when a receptor becomes insurmountable?
A process called desensitization; the cell degrades the receptor shutting down the signaling process. It is a protective mechanism for the cell
What makes a good receptor?
-Increased selectivity: binds to 1 drug or 1 drug type
-Alteration: In order for the downstream effect to occur, the receptor has to be altered after the drug binds.
What makes a bad receptor?
-No alteration: “inert binding sites” No detectable change in function after binding therefore the drug has no effect on the body
- Non-selective: Bind to just any drugs
What is the most important plasma protein?
Albumin
Describe Albumin.
Large and doesn’t cross barriers easily; when bound to drugs the drugs also cannot cross barriers.
What are Drug Carriers?
They are used to get drugs where they need to go
When can a drug cross a barrier?
When it is in its free form it can diffuse into tissue and bind to receptors
What can affect the levels of albumin in the body? What happens to drugs in the body when this happens?
-Malnutrition, liver damage Kidney failure
-The amount of free drug in the CVS will increase d/t not having enough of albumin to bind to. You will see increased effects, increased toxicity and increased negative side effects.
Albumin bound is ______. Receptor bound is ______.
Bad
Good
What drug is highly bound to albumin?
Phenytoin
What drug competes for binding sites with phenytoin? What is the result of this?
-Carbamazepine (another anti-seizure)
-Because of this you will see an increased concentration of free drug of both of these drugs
What are the 3 drug carriers?
Albumin
Alpha-1 glycoprotein
Lipoproteins
What type of drug does Albumin mostly bind to?
Acidic drugs
What type of drug does Alpha-1 glycoproteins mostly bind to?
Basic drugs
What type of drugs does Lipoproteins mostly bind to?
Neutral drugs
What is the definition of drug concentration?
The amount of drug in the plasma
What is the definition of drug dose?
How much I gave the patient (think of how the concentration would differ if you give PO vs IV even though it is the same dose)
What is potency?
Concentration (EC50) or dose (ED50) of a drug required to produce 50% of that drugs maximal effect. The greater the effect at 50% = higher potency
What is maximal efficacy?
It is the most important!
It is the max response a drug can deliver; varies per drug
What does the maximal efficacy depend on?
Drug interaction with the receptor
Although maximal efficacy is most important, what should you take into account?
DRUG TOXICITY
Think: Although this drug has a high maximal efficacy, what toxic side effect will I see at that max response? What dose/concentration will I have to give the patient to see these results? Will the benefits outweigh the risks?
The larger the therapeutic index, the ______ the drug
Safer
What is the Median Effective Dose (ED50)?
Where 50% of the population will see effectiveness of a given dose
What is the Median Toxic Dose (TD50)?
Where 50% of the population will see toxic side effects at a given dose
What is the Median Lethal Dose (LD50)?
It is not used in humans!!
Where 50% of the population will have lethal side effects
What does the therapeutic index do?
Establishes the margin of safety
ED50 vs TD50
Shows effectiveness vs toxicity
In animals, how do you find the therapeutic index?
LD50 / ED50
In humans, how do you find the therapeutic index?
TD50 / ED50
What does a narrow therapeutic index indicate? Give an example
That the dose is more toxic. Need to monitor closely. A very small increase in dose could have negative SE
Digoxin; warfarin; lithium
What does a wide therapeutic index indicate? Give an example
That the drug is safer. Small increases in drugs are less likely to have negative SE.
Ibuprofen; Tylenol; Antihistamines
What has an affect on drug responsiveness?
Polypharmacy (Drug-drug interactions); genetic factors; idiosyncratic (usual drug response with no reason why; maybe genetics); tolerance; tachyphylaxis; chemical antagonist; physiologic antagonism
What is tolerance? Give an example
The response decrease over the course of therapy; needing a higher dose for previous response.
-Morphine
What does tachyphylaxis mean?
Developing a quick tolerance
How does a chemical antagonist attribute to drug responsiveness in a patient?
If a patient is taking another drug that is binding to the same receptor that we need for another drug that we are giving, we will see decreased results.
What factors can cause an alteration in the concentration of a drug in the body?
The rate of absorption, distribution, and clearance can be affected by age, weight, sex, disease state (liver/kidney failure)
How does the endogenous ligand effect drug responsiveness?
The endogenous ligand may be affected by your health. This can cause less or more of the endogenous ligand to bind to receptors that are meant to be bound to a drug we are giving. If it’s less of the endogenous ligand then the effect of the drug will increase. if it’s more, then the effect of the drug will decrease.
How does the function or number of receptors effect drug responsiveness?
The more functional receptors you have, you will see an expected response from the drug.
If you have less receptors or receptors that are not functional;, then you’ll see less of a response of the drug.
How does the alteration of the receptor affect drug responsiveness?
This refers to the downstream response of the receptor. This is the largest and most important cause of variation in drug responsiveness referred to as “post receptor process”; if there is no alteration then there is no downstream effect therefore decreasing drug responsiveness.
What is an example of a drug that has both desired and adverse side effects at the same receptor? Example?
Recemic mixtures
Esketamine and R-ketamine.
A drug needs to be _______ to cross barriers?
Uncharged
Can drugs with small charges cross barriers?
Yes.
Why do drugs need to mostly be uncharged to cross barriers?
The inner cell wall is hydrophobic (uncharged) then the drug should be too so it can cross easily. The uncharged drug can go through the polar head (charged) portion on the cell wall fine.
What is a weak acid?
pH below 7.5
Releases H+ into solution (-)
What is a weak base?
pH above 7.5
Absorbs H+ from solution (+)
What is pKa?
Dissociation constant
What does the Henderson Hasselbach Equation do?
It relates pH to pKa and vice versa
if pH < pKa then
favors protonated form
Has [H+] attached
if pH > pKa then
favors unprotonated form
No [H+] attached - not attached.
Why is protonated vs non protonated important?
Protonated has a harder time crossing barriers
In a weak acid, the pH < pKa…
protonated; uncharged
In a weak acid, the pH > pKa…
unprotonated; charged
In a weak base, the pH < pKa
protonated; charged
In a weak base, the pH > pKa
unprotonated; uncharged
How do you identify a protonated compound vs an unprotonated compound?
In a protonated compound the H attached!!! In unprotonated, the H will be + H+
What is the pH in the stomach?
1.5
Where are most drugs filtered?
In the Kidneys at the glomerulus
What is -MAB
Monoclonal Antibody
It is a protein drug that is produced by clones of a single plasma cell
What is special about -mab drugs?
They bind to a specific antigen/targer/receptor in the body. With increased specificity there is a decrease in adverse effects.
A -mab can also cause cell ____________ by various mechanisms. Example.
Death
In cancer cells it shuts down the growth of a cncer cell and binding to that specific receptor
What are the 2 major functions of -mab?
-Recognize and bind to a specific antigen
-Induce immune response after binding
What variables mediate binding?
Affinity and specificity for a specific receptor
How are -mab made?
- Mice are injected with a diseased cell/virus to make antibodies (immunized with an antigen)
- When specific titer is reached, mice are euthanized and the spleen is removed
- Plasma cells are harvested from the spleen because that’s where the antibody are produced
- Spleen cells are fused with immortal myeloma cells
- New cell is cloned and tested for antibodies
- The cells positive for the antibodies are cloned in vitro
- Cells are harvested
What is a myeloma cell?
A cancer cell that gets fused with a plasma cell to make it immortal
What differentiates the humanized antibody vs the chimeric antibody?
humanized is mostly human with a small amount of mouse and chimeric has a larger portion of mouse
What is the organization that gets the drugs on the market?
Food and Administration (FDA)
About how many new drugs are approved per year?
50-60 drugs
What does the FDA regulate?
-The specific claims you can make about drugs
-The safety and effectiveness of drugs; if not safe, wont approve
-What category a drug should be placed in: OTC or prescription (BTC); herbal or medicine
What does the FDA deem to have to be safe but not effective?
Vitamins
What is phocomelia?
The lack in development of limbs
What is a teratogen?
A drug that crosses the placenta and can cause birth defects
What drug in the 1950s was a teratogen and caused phocomelia?
Thalidomide was introduced for morning sickness
After how many days can you submit an FDA application after denial?
After 60 days a company can resubmit an application for approval
What is Thalidomide used for now?
Multiple myeloma; cannot be pregnant while using
Who was instrumental in the FDA refusal of Thalidomide?
Frances Kathleen Oldman Kelsey, Ph.D., M.D.
Describe the clinical testing process
All human studies; takes about 4 years
1. Phase 1: 20-100 healthy volunteers; just trying to make sure drug is safe
2. Phase 2: 100-200 patients; double blind: 100 placebo vs 100 drug; trying to see if this drug is actually effective in humans.
This is normally where most drug trials end because they arent effective.
3. Phase 3: 1000-6000 patients; If drug worked well, will skip double blind and just give drug to all patients; Market formulation starts here
What does IND mean?
Investigational new drug
What does NDA mean?
New drug application; at the end of Phase 3; Doctors can start to prescribe drug
How long can an NDA take?
1 year
How long does the In vitro studies last?
2 Years
How long does animal studies last?
2 years
What is the definition of a receptor?
Component that interacts with a drug and initiates a chain of events leading to the drug’s observed effects
Receptor affinity determines ________
Dose
What does receptor selectivity refer to?
Somg drugs bind to only 1 receptor while other may bind to multiple receptors.
Specific - 1 drug vs non specific - multiple
What does an allosteric inhibitor do?
Blocks/inactivates receptor although theres nothing bound to the active site
A receptor is a _______
Protein
What does a regulatory protein do?
effects transcription and translation
Where does an endogenous ligand bind?
At the active site
What are orphan receptors?
A receptor that has no known endogenous ligand; this is about half of the receptors in the body.
What is GPCRs?
G-Protein coupled receptors; 7 transmembrane receptor (7TM)
About ______ of all non antibiotic drugs bind to and activate the GPCRs
2/3
What is a Ligand-gated channel?
Opens a channel when something binds to it
Where are enzymes normally located?
Close to a receptor
Describe the cell signaling process
- The neuron releases endogenous ligand or drug in the CVS (1st messenger; signaling molecule)
- Attaches to receptor
- Signaling transduction proteins are activated (2nd messengers)
- These trandsuction proteins activate the effector protein which allows for the modification of cellular metabolism/function/movement. This is where you get the effects of the drug or the endogenous ligand
What is a lag period?
The amount of time it takes for transcription and translation by the proteins; responses can be seen anywhere between 30 minutes to several weeks; not all drugs have a lag period
What does persistence mean?
The effects of a drug last very long so you have to give it less often; Protein degradation pathways vary
Describe the Phosphorylation Cascade
- Drug binds to receptor
- Receptor has conformational change
- Receptor activates Kinase
- Kinase attaches to protein, attaches a phosphate and activates it; Protein 1-PO4 (Protein-kinase)
- That protein 1-PO4 activates another protein; protein 2-PO4
- This process continues until the effector protein is activated
What is the effector protein?
The effector protein is where you’ll see the response of the receptor or the effect of the drug/endogenous ligand. This is where the cell will experience a modification in metabolism, function, or movement
Are intracellular receptors charged or uncharged?
Uncharged
What does the G mean in G-protein?
Guanine triphosphate
What processes deal with multiple signaling?
GPCR and Phosphorylation cascade
About how many GPCR are there?
500 identified; 500 orphans
What are G-proteins made from?
3 amino acids that function together; Trimeric: Alpha beta, gamma
GDP is ____________
GTP is _____________
Inactive
Active
What does Pleiotropy mean?
Several possible downstream effects from a single receptor
Describe a GPCR
A receptor protein motif that crosses the membrane 7 times
What does the beta and gamma amino acids do?
They help with the binding to the receptor (they dont move)
What does the alpha amino acid do?
binds to the GDP/GTP to activate; most important one
Where does the ligand bind to GPCR?
On the receptor somewhere on the outside of the cell on the NH3+ end
Where does the G protein bind to the GPCR?
Somewhere inside the cell on the COO- end
Describe the GPCR process
- ligand binds to NH3+ part of receptor on outside of cell (1st messenger)
- GDP is ALREADY ATTACHED to G-protein at alpha on the COO- end of the receptor on the inside of the cell
- Conformational change activates the alpha; Now alpha can bind to GTP
- GDP is released into cytosol
- The alpha is released into the cytosol and activates an effector protein
- Once the effector protein is activated; the drug unbinds from the receptor
- An inactived alpha with an attached GDP returns to the beta and gamma amino acids to reform a whole G-protein
- Process starts over :)
What is cAMP?
Cyclic AMP and it is considered a second messenger; 2nd messengers are a part of the transcription process which can effect the time it takes to reach the effector protein to see a response.
List Receptor type based on molecular structure
-GPCRs
-Ligand-gated channels
-Ion channels
-Catalytic receptors
-Nuclear receptors
-Transporters
-Enzymes
Describe the cell signaling process
- Endogenous ligand is released from a neuron or an exdogenous ligand is put into the CVS.
- The ligand is the 1st messanger. The lingand binds to the receptor.
- The receptor undergoes a conformational change which activates the signaling tranduction protiens (second messengers such as cAMP)
- The effector protein is activated and eliciets the response of the ligand
Draw a phosphorylation cascade (generic).
Refer to picture
Name 4 transmembrane signaling methods by which drug-receptor interactions exert their effects?
- Intracellular receptors (Nuclear receptor)
- Ion channels
- Catalytic receptors (RTKs)
- GPCRs
Define the structure of GPCRs and RTKs, including their components.
GPCRs
7 transmembrane receptor with an NH3+ beginning and an COO- end. The G protein is a trimeric amino acid that consist of an Alpha, Beta, and Gamma animo acid. The G-protein attaches at the COO- end and and ligand attaches at the NH3+ end. The Beta and Gamma stay attached to the receptor while the Alpha can have either a GDT or GTP attached and attach to an effector protien to cause an effect within the cell.
RTKs (Receptor Tyrosine Kinases)
You have to have 2 monomers (and 2 ligands); the monomers have 3 -Tyr (tyrosines) on them. They dimerize (become 1) and become phosphoriated to activate.
What does Adenylyl cyclase do?
When G-protein attaches to Adenylyl cyclase it cycles ATP into cAMP (Cyclic AMP)
What does cAMP do?
Cyclic AMP is the second messenger; it activates protein-kinase (Protein-PO4) which leads into the phosphorylation cascade
Adenylyl cyclase and Phospholipase are both ________ and __________ proteins
Enzymatic and effector
What does Phospholipase C do?
-Turns into PIP2
-Turns into DAG
-DAG (Diacylglycerol) releases IP3 (Inositol triphosphate)
-IP3 (a second messenger) attaches to a IP3-gates calcium channel on the ER which allows the gate to open and calcium to flood into the cell.
-Calcium flooding out the cell acts as a second messenger and activates a cellular response.
Describe the role of second messengers, and list the most common as described in lecture
The role of the second messenger acts as an enzyme. Once the G-protein attaches to it amplifies the signal of the first messenger (ligand).
Common second messengers:
-IP3
-Ca++
-cAMP
-DAG
What is Calciums role in the cell?
Acts as a second messenger; released from the cell by IP3 binding to the IP3 gated Calcium channel; it is released into the cell and activates various protiens for a cellular response.
Define desensitization and describe the molecular components of desensitization in the GPCR
Desensitization refers a process where cell reduces its responsiveness to a stimulus over time.
-After prolonged stimulus the inside of the receptor becomes phosphorated with 3x -OH.
-Beta Arrestin binds to the -OH which shuts down the signaling of the receptor.
-That receptor is then moved along the cell wall into a clathrin coated pit where the entire receptor,drug, and beta arrestin are swallowed
-1: A Lysosome merges with the compound and degrades it and excretes the drug or 2: covalent bond breaks and recyclin merges with it and recycles the receptor back to the surface of the cell and frees the drug back into the ECF
Differentiate ligand gated and voltage gated ion channels.
A ligand gated channel opens when bound to a specific ligand
A voltage gated ion channel opens and closes in response to changes in membrane potential d/t an action potential
What is the difference between a kinase and a phosphatase?
Tyrosine Kinase add a phosphate to a protein
Tyrosine Phosphatase takes a phosphate from a protein.
What are the 4 catalytic cell receptors?
Tyrosine Kinase
Tyrosine Phosphatase
Serine/Threonine Kinase
Guanylate cyclase (GTP)
Distinguish ionotropic and metabotropic ion channels
Ionotropic channels are more common. A ligand binds to a site, activates it, and opens a channel on same protein/site
Ex) nAch receptor
A metabotropic ion channel is opened by a second messenger from a ligand activated GPCR
Describe the process of Receptor Tyrosine Kinase.
-2 monomers-receptors with intracelluar tyrosine kinase domains and bound by ligands.
-They dimerize (become one) and become phosphoriated (Tyrosine PO4) which activates them
-The active form of the receptor uses 6 ATP molecules
-The receptor then activates the effector protein which has the cellular response/downstream effect
_______ in the cell surface allows the passage of _______
Pores
Ions
Describe the voltaged gated channels at:
Closed
Activated
Inactivated
Deactivated
Closed: M-gate closed; H-gate open
Activated: Both gates open
Inactivated: M-gate opened; H-gate closed
Deactivated: Both gates closed
List the types of ligands that bind to receptors inside the cell
-Steroid hormones
-Thyroid hormones
-Vitamin D
-Retinoic Acid
