G Protein Coupled Receptors (GPCRs)

Question 1

What is the significance of G Protein-Coupled Receptors (GPCRs) in drug targeting?

Answer 1

GPCRs are significant because approximately 50% of drug targets are GPCRs, highlighting their importance in pharmacology and therapeutic interventions.

Question 2

How many types of GPCRs are there?

Answer 2

There are over 1000 types of GPCRs, each specific to certain ligands and signalling pathways.

Question 3

What role do GPCRs play in cellular signalling?

Answer 3

GPCRs respond to hormones, neurotransmitters, and lipids by detecting extracellular signals and inducing cellular responses through a second messenger system.

Question 4

Describe the structure of GPCRs.

Answer 4

GPCRs have a structure characterized by 7 transmembrane domains and a heterotrimeric G protein complex composed of alpha, beta, and gamma subunits.

Question 5

How do GPCRs transduce signals from extracellular to intracellular effects?

Answer 5

GPCRs bind specific ligands at their N terminal, which activates intracellular signalling pathways, leading to various cellular responses.

Question 6

What is an example of a GPCR and its function?

Answer 6

An example is adrenoreceptors, which respond to adrenaline and noradrenaline, producing different physiological effects in the body based on the receptor subtype and tissue expression.

Question 7

What determines the signalling response of G proteins?

Answer 7

The composition of the heterotrimer (the specific types of alpha, beta, and gamma subunits) determines the signalling response, with over 20 types of alpha subunits including G alpha s, G alpha i, and G alpha q.

Question 8

What are IP3 and DAG, and what role do they play in GPCR signalling?

Answer 8

IP3 (inositol trisphosphate) and DAG (diacylglycerol) are second messengers produced following GPCR activation, and they play critical roles in propagating the signal within the cell.

Question 9

What is the importance of ligand specificity in GPCR function?

Answer 9

Ligand specificity is crucial because different GPCRs respond to different ligands, which can lead to varied effects depending on the receptor type and its location in the body.

Question 10

What happens when a GPCR is activated?

Answer 10

Upon activation, GPCRs undergo a conformational change that allows them to activate associated G proteins, which then initiate a signalling cascade inside the cell.

Question 11

How can the same ligand produce different effects in the body?

Answer 11

The same ligand can produce different effects depending on the type of GPCR it binds to and the specific tissues where those receptors are expressed.

Question 12

What is the role of G alpha subunits in GPCR signalling?

Answer 12

G alpha subunits play a key role in determining the downstream signalling pathways activated by GPCRs, influencing cellular responses such as enzyme activation or inhibition.

Question 13

What types of extracellular signals can GPCRs detect?

Answer 13

GPCRs can detect various extracellular signals, including hormones, neurotransmitters, and lipids.

Question 14

What is the function of the heterotrimeric G protein complex associated with GPCRs?

Answer 14

The heterotrimeric G protein complex transmits signals from the activated GPCR to intracellular effectors, mediating the cellular response.

Question 15

What occurs at the N terminal of GPCRs?

Answer 15

The N terminal of GPCRs is where specific ligands bind, triggering the receptor’s activation and subsequent intracellular signalling.

Question 16

How do different GPCRs contribute to pharmacological diversity?

Answer 16

Different GPCRs can activate various signalling pathways and produce distinct cellular responses, allowing for a wide range of pharmacological effects from the same ligand.

Question 17

What are the major types of G alpha subunits and their functions?

Answer 17

The major types of G alpha subunits include G alpha s (stimulatory), G alpha i (inhibitory), and G alpha q (activates phospholipase C), each influencing different downstream signalling pathways.

Question 18

What is the role of second messengers in GPCR signalling?

Answer 18

Second messengers, like IP3 and DAG, amplify the signal initiated by GPCR activation and facilitate communication within the cell, leading to various physiological responses.

Question 19

Why is understanding GPCR signalling important in drug development?

Answer 19

Understanding GPCR signalling is crucial for drug development because many therapeutic agents target these receptors to modulate their activity and achieve desired therapeutic effects.

Question 20

How can the expression pattern of GPCRs affect drug response?

Answer 20

The expression pattern of GPCRs in different tissues can affect how a drug interacts with the receptor and the resulting physiological effects, leading to variability in drug efficacy and side effects.

Question 21

What types of pharmacological agents can target GPCRs?

Answer 21

Various pharmacological agents, including agonists, antagonists, and allosteric modulators, can target GPCRs to either activate or inhibit their signalling pathways.

Question 22

How do GPCRs participate in sensory perception?

Answer 22

GPCRs are involved in sensory perception processes such as smell and taste, where specific ligands (odorants and tastants) activate the receptors to initiate sensory signals.

Question 23

What mechanisms can lead to desensitization of GPCRs?

Answer 23

Desensitization of GPCRs can occur through phosphorylation, internalization, or recruitment of regulatory proteins, reducing the receptor’s responsiveness to its ligand over time.

Question 24

Can GPCRs interact with multiple signalling pathways?

Answer 24

Yes, GPCRs can interact with multiple signalling pathways, which allows for complex regulation of cellular functions and diverse physiological effects.