Nuclear Receptors and Glucocorticoid Receptor
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Questions and Answers

Where are nuclear receptors typically located in a cell?

Intracellular

What is the effect of glucocorticoid drugs such as prednisolone?

Anti-inflammatory

What is the difference between an agonist and an antagonist?

Agonists bind to and activate receptors, while antagonists bind to, but do not activate receptors

How do blockers work on ion channels?

<p>By physically plugging the ion channel</p> Signup and view all the answers

What is an example of a substrate analogue inhibitor?

<p>Analgesics like paracetamol, which inhibit cyclooxygenase</p> Signup and view all the answers

What is the function of Gaq protein in G protein-coupled receptors?

<p>Phospholipase C activation, generating inositol trisphosphate and diacylglycerol as second messengers</p> Signup and view all the answers

What is an example of a false substrate for an enzyme?

<p>Anti-cancer drug fluorouracil, which replaces uracil in purine biosynthesis</p> Signup and view all the answers

What is the effect of GPCR activation in airway smooth muscle?

<p>Relaxation</p> Signup and view all the answers

What is an example of a pro-drug?

<p>Ciclesonide, which is converted to the active metabolite in the lung</p> Signup and view all the answers

What is the location of enzyme-linked receptors and what do they respond to?

<p>Membrane-bound, responding to metabolism, growth, and differentiation</p> Signup and view all the answers

What is the function of transporters in cells?

<p>To transport ions and small organic molecules across cell membranes</p> Signup and view all the answers

What is the function of the enzyme tyrosine kinase in insulin receptor signaling?

<p>Phosphorylation of intracellular proteins</p> Signup and view all the answers

What is the role of Gs protein in GPCR signaling?

<p>Stimulatory, activating adenylate cyclase to generate cAMP</p> Signup and view all the answers

What type of receptor is responsible for the action of insulin in reducing blood glucose levels?

<p>Enzyme-linked receptor</p> Signup and view all the answers

What is the time scale of action for enzyme-linked receptors?

<p>Minutes, slow</p> Signup and view all the answers

What is the common feature of GPCRs, enzyme-linked receptors, and nuclear receptors?

<p>Respond to extracellular signals</p> Signup and view all the answers

What is the primary mechanism of signal transduction for G protein-coupled receptors?

<p>Activation of G proteins, which in turn activate downstream effectors, such as adenylate cyclase or phospholipase C, leading to changes in second messenger systems.</p> Signup and view all the answers

What is the primary difference between enzyme-linked receptors and G protein-coupled receptors?

<p>Enzyme-linked receptors have intrinsic enzyme activity, whereas G protein-coupled receptors rely on activation of separate G proteins to initiate signaling.</p> Signup and view all the answers

What is the role of agonists in receptor-ligand interactions?

<p>Agonists bind to receptors, activating them and triggering a response, often mimicking the action of endogenous ligands.</p> Signup and view all the answers

What is the time scale of action for G protein-coupled receptors?

<p>Milliseconds to seconds, depending on the specific receptor and signaling pathway.</p> Signup and view all the answers

What is the primary function of second messenger systems in signal transduction pathways?

<p>To amplify and distribute the signal from the receptor to downstream effectors, often involving activation of protein kinases or other enzymes.</p> Signup and view all the answers

What is the main characteristic feature of ion channel receptors?

<p>Directly regulating ion flow across the plasma membrane, often leading to rapid changes in membrane potential or electrical activity.</p> Signup and view all the answers

What is the role of G proteins in signal transduction pathways?

<p>To act as molecular switches, transmitting signals from activated receptors to downstream effectors, such as adenylate cyclase or phospholipase C.</p> Signup and view all the answers

What is the primary difference between receptors and enzymes as drug targets?

<p>Receptors respond to ligand binding, whereas enzymes are targets for inhibitor or activator molecules that modulate their activity.</p> Signup and view all the answers

What is the key characteristic that distinguishes receptor superfamilies?

<p>How they transduce the signal</p> Signup and view all the answers

What is the role of ACh binding in nicotinic acetylcholine receptors?

<p>ACh binding alters ion channel structure and ions flow into the cell</p> Signup and view all the answers

What is the common feature of ion channel receptors?

<p>Collection of proteins form central pore / channel</p> Signup and view all the answers

What happens to the ion channel when no agonist is present in ion channel receptors?

<p>The ion channel is closed, and no ion flow occurs</p> Signup and view all the answers

What is the primary function of ion channel receptors?

<p>To regulate ion flow into the cell</p> Signup and view all the answers

How do ion channel receptors respond to agonist binding?

<p>The ion channel structure changes, allowing ions to flow into the cell</p> Signup and view all the answers

What is the significance of receptor superfamilies in understanding signal transduction?

<p>Receptors within a superfamily use similar transduction processes and have similar structures</p> Signup and view all the answers

What is the key aspect of signal transduction in ion channel receptors?

<p>Direct ion flow into the cell</p> Signup and view all the answers

Where are ion channel receptors typically located in a cell?

<p>membrane</p> Signup and view all the answers

What is the time scale of action for ion channel receptors?

<p>milliseconds</p> Signup and view all the answers

What type of receptors do hormones and slow neurotransmitters typically bind to?

<p>G protein-coupled receptors</p> Signup and view all the answers

What is the function of the Ga protein subunit in G protein-coupled receptors?

<p>activates adenylate cyclase</p> Signup and view all the answers

What is the purpose of using Pancuronium in anaesthesia?

<p>to produce paralysis</p> Signup and view all the answers

What type of receptors do Salbutamol and muscarinic acetylcholine receptors belong to?

<p>G protein-coupled receptors</p> Signup and view all the answers

What is the role of GDP and GTP in G protein-coupled receptors?

<p>guanosine nucleotide binding proteins</p> Signup and view all the answers

How many transmembrane domains do G protein-coupled receptors typically have?

<p>7</p> Signup and view all the answers

Study Notes

Nuclear Receptors

  • Location: intracellular
  • Effector: gene transcription
  • Respond to: steroid hormones, other factors
  • Time scale of action: hours, very slow
  • Examples: glucocorticoid, other steroid hormones

Glucocorticoid Receptor

  • Responds to cortisol and glucocorticoid drugs like prednisolone, which are effective anti-inflammatory agents

Protein Targets for Drug Action

  • Receptors
    • Agonists bind to and activate receptors
    • Antagonists bind to, but do not activate receptors
  • Ion channels
    • Blockers physically plug the ion channel
    • Modulators bind to accessory sites and modulate channel activity
  • Enzymes
    • Substrate analogues competitively inhibit the enzyme
    • Some drugs act as false substrates for enzymes
    • Pro-drugs must be enzymatically converted to become active
  • Transporters
    • Specific carrier proteins transport ions and small organic molecules across cell membranes

Receptor Superfamilies

  • 4 major types: ion channel receptors, G protein-coupled receptors, enzyme-linked receptors, and nuclear receptors
  • Distinguished based on how they transduce the signal, not on which chemical signals stimulate them or the nature of the change in cell function

Ion Channel Receptors

  • Location: cell membrane
  • Collection of proteins form central pore/channel
  • No agonist, ion channel closed, no ion flow

Enzyme-Linked Receptors

  • Location: membrane
  • Effector: enzyme
  • Respond to: metabolism, growth, differentiation
  • Time scale of action: minutes, slow
  • Examples: insulin receptor, receptors for cytokines, growth factors

Insulin Receptor

  • Insulin binds to receptor, reducing blood glucose levels in diabetes

G Protein-Coupled Receptors

  • Location: membrane
  • Effector: enzyme or channel
  • Respond to: hormones, slow neurotransmitters
  • Time scale of action: seconds, fast
  • Examples: adrenoceptors, muscarinic acetylcholine receptors

G Proteins

  • Intracellular effector systems or 2nd messenger cascades
  • Guanosine nucleotide binding proteins, GTP and GDP
  • Comprise 3 subunits (a, b, g)
  • Main classes of Ga protein: Gas activates adenylate cyclase, Gai inhibits adenylate cyclase

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Description

This quiz covers the characteristics of nuclear receptors, their location, effectors, and response to steroid hormones. It also delves into the glucocorticoid receptor and its response to cortisol and glucocorticoid drugs.

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