G Protein Coupled Receptors (GPCRs)
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Questions and Answers

What is the main mechanism by which a drug or hormone signal is transmitted into the cell via GPCRs?

G Protein

How many transmembrane helices do all GPCRs have in common?

7

What distinguishes Family A GPCRs from Family B GPCRs in terms of their structure?

Family A do not typically have an extracellular domain, while Family B GPCRs do.

What is the study of how individual genetic differences can influence how drugs work through receptors called?

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

What must be done to study GPCRs, considering their microenvironment and structure?

<p>Purify them using detergents to solubilize them</p> Signup and view all the answers

Where is the orthosteric binding pocket located in the Beta 2 Adrenergic Receptor?

<p>⅓ of the way into the transmembrane helix (extracellular half of the receptor)</p> Signup and view all the answers

What is the main role of Beta 2 Adrenergic receptors in heart failure?

<p>Involved in heart failure</p> Signup and view all the answers

How does Propranolol act on Beta 2 Adrenergic receptors?

<p>Blocks the Beta 2 Adrenergic receptor</p> Signup and view all the answers

Explain the concept of GPCR cross reactivity.

<p>Similar orthosteric location in the receptor</p> Signup and view all the answers

What is drug repositioning/repurposing in the context of GPCRs?

<p>Using existing drugs to treat different disease states</p> Signup and view all the answers

Describe the role of glycosylation in proteins.

<p>Adding sugars onto the protein to protect it</p> Signup and view all the answers

What are the three subunits that make up a G protein?

<p>Alpha, beta, gamma</p> Signup and view all the answers

What percentage of disease states concerning membrane proteins are accounted for by mutations in the conserved amino acids?

<p>87%</p> Signup and view all the answers

What is the role of cholesterol in GPCR function?

<p>Specific cholesterol binding site on the external surface of the receptor</p> Signup and view all the answers

How do mutations in a conserved Tryptophan affect GPCRs?

<p>Responsible for various conditions like dementia and certain cancers</p> Signup and view all the answers

Explain the concept of allosteric regulation in GPCRs.

<p>Modulating receptor function by binding to sites other than the orthosteric pocket</p> Signup and view all the answers

Study Notes

G Protein-Coupled Receptors (GPCRs)

  • GPCRs are a collective term for membrane proteins that share a common mechanism of signaling
  • They have a common structure, with 7 transmembrane helices
  • Approximately 800 different GPCRs exist in humans, divided into classes (e.g., Family A and Family B)
  • Family A GPCRs typically lack an extracellular domain, whereas Family B GPCRs have an extracellular domain

Function and Mechanism

  • A drug or hormone binds to a GPCR, and the signal is transmitted into the cell via a G Protein
  • The signal is transmitted through a mechanical conformational shape change in the receptor
  • This allows recruitment of a G protein at the intracellular side, which is composed of 3 subunits (alpha, beta, and gamma)

Microenvironment and Post-Translational Modifications

  • The microenvironment of GPCRs influences their function (e.g., lipids surrounding the receptor and interacting proteins)
  • Glycosylation (addition of sugars) and disulfide bonds (between cysteine amino acids) are important for GPCR structure and function

Orthosteric Binding Site and Conformational Change

  • The orthosteric binding site is the main binding site for the ligand, located in the transmembrane helix
  • The binding of a ligand induces a conformational change, allowing recruitment of the G protein

Disease and Mutations

  • Mutations to conserved amino acids in the center of the receptor account for 87% of disease states concerning membrane proteins
  • Mutations can either stop signal transmission, increase sensitivity, or cause constitutive activity

Cholesterol Binding and Allosteric Regulation

  • All GPCRs have a specific cholesterol binding site located on the external surface of the receptor
  • Cholesterol binding is necessary for GPCR function; without it, receptors may activate spontaneously or not operate at all
  • Allosteric regulation of GPCRs by cholesterol modulates the function of the orthosteric pocket

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Description

Explore the world of G Protein Coupled Receptors, a group of membrane proteins sharing a common signaling mechanism. Learn about how drugs and hormones bind to GPCRs to transmit signals into cells via G Proteins, and understand the common structural features of GPCRs with 7 transmembrane helices.

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