Signal traduction GPCRs week 26

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121 Questions

G-protein-coupled receptors (GPCRs) are not involved in signal transduction pathways?

False

The role of GPCRs in the actions of neurotransmitters & hormones is not discussed in this lecture?

False

cAMP and IP3/Ca2+ are not considered as second messengers in GPCR signalling?

False

GPCR desensitisation & intracellular trafficking are not important aspects discussed in this lecture?

False

G-proteins have no role in GPCR signalling?

False

When an agonist drug binds to its receptor, a drug-receptor (D-R) complex is not formed.

False

Signal transduction involves the activation of relay proteins and production of second messengers inside the cell.

True

There are 4 major signal transduction pathways, including activation of receptor-ion channels.

True

G-protein-coupled receptors constitute the largest receptor superfamily in humans, with approximately 800 members.

True

G-protein-coupled receptors transduce a narrow array of extracellular signals and regulate only specific aspects of physiology.

False

G-protein-coupled receptors are not involved in mediating responses to vision, olfaction, or taste signals.

False

All G-protein-coupled receptors share a common structural motif of seven transmembrane (7-TM) α-helices.

True

G-protein-coupled receptors do not couple to and activate cytoplasmic heterotrimeric G-proteins upon agonist binding.

False

The extracellular region of a GPCR modulates ligand access to the binding site on the receptor.

True

The intracellular region of a GPCR interfaces with extracellular signaling proteins.

False

Heterotrimeric G-proteins are composed of 2 different protein subunits: ,  and .

False

The Gα subunit harbors a guanine nucleotide-binding site, which is occupied by GTP in the inactive resting (off) state.

False

The N-terminus of Gα is myristoylated or palmitoylated, which results in the attachment of the G protein to the nucleus.

False

G-protein signaling via heterotrimeric G-proteins translates agonist-GPCR binding into modulation of activity of downstream extracellular effector proteins.

False

Regulators of G-protein signaling (RGS) proteins or GTPase-accelerating proteins (GAPs) slow down the hydrolysis of GTP to GDP in the Gα subunit.

False

Gα proteins are grouped into 4 families based on their peptide sequence & functional similarities – Gαs, Gαi, Gαq/11, and Gα12/13 protein families.

True

Gαi family stimulates adenylate cyclase resulting in increased cAMP levels.

False

Gαq/11 family stimulates phospholipase C-β resulting in increased IP3 & DAG levels.

True

Most Gα proteins mediate GPCR signaling by regulating the levels of extracellular regulatory molecules called second messengers.

False

The cAMP signaling pathway is activated when Gs-GTP inhibits Adenylyl Cyclase (AC), resulting in decreased cAMP levels.

False

The Inositol 1,4,5-trisphosphate/calcium signaling pathway is activated when Gq/11-GTP activates Phospholipase C-β (PLCβ), resulting in increased IP3 & DAG levels.

True

What is the key function of G-protein-coupled receptors (GPCRs) in signal transduction?

Coupling to and activation of cytoplasmic heterotrimeric G-proteins upon agonist binding

Which major role do Gαq/11 family play in GPCR signaling?

Stimulating phospholipase C-β resulting in increased IP3 & DAG levels

What is the main structural motif shared by all G-protein-coupled receptors (GPCRs)?

Seven transmembrane (7-TM) α-helices

Which molecules act as second messengers in GPCR signaling?

$cAMP$ and $IP3/Ca^{2+}$

What is the outcome of Gs-GTP inhibiting Adenylyl Cyclase (AC) in GPCR signaling?

Decreased cAMP levels

What happens when an agonist drug binds to its receptor in GPCR signaling?

Formation of a drug-receptor (D-R) complex

What is the main role of Regulators of G-protein signaling (RGS) proteins or GTPase-accelerating proteins (GAPs) in GPCR signaling?

$GTP$ hydrolysis acceleration in the Gα subunit

What does the intracellular region of a GPCR interface with?

Extracellular signaling proteins

What is activated when Gq/11-GTP activates Phospholipase C-β (PLCβ) in GPCR signaling?

$IP3$ production inside the cell

What is the outcome when an agonist drug binds to its receptor, leading to the formation of a drug-receptor (D-R) complex?

Increased cAMP levels

What is the process called when an agonist drug binds to its receptor and triggers a chain of biochemical processes inside the cell?

Signal transduction

Which type of receptors constitute the largest receptor superfamily in humans, with approximately 800 members?

G-protein-coupled receptors

What is the common structural motif shared by all G-protein-coupled receptors?

Seven transmembrane (7-TM) α-helices

What is the role of G-protein-coupled receptors in mediating responses to hormones, neurotransmitters, and growth factors?

Mediates responses to hormones, neurotransmitters, and growth factors

Which pathway is activated when Gs-GTP inhibits Adenylyl Cyclase (AC), resulting in decreased cAMP levels?

cAMP signaling pathway

What is the main function of G-protein-coupled receptors in signal transduction pathways?

Activation of relay proteins & production of second messengers inside the cell

What is the name for the group of receptors with a similar basic molecular structure and that use the same signal transduction pathway?

Receptor superfamily

Which type of receptors are used by cells to convert extracellular signals into intracellular responses?

G-protein-coupled receptors

What process occurs when Gq/11-GTP activates Phospholipase C-β (PLCβ), resulting in increased IP3 & DAG levels?

IP3/Ca2+ signaling pathway

What is the function of heterotrimeric G-proteins in GPCR signaling?

Convey signals from cell-surface GPCR to downstream intracellular effector proteins

What is the composition of heterotrimeric G-proteins?

3 different protein subunits: α, β, and γ

What is the role of the Gα subunit in the resting state of heterotrimeric G-proteins?

Harbors a guanine nucleotide-binding site, which is occupied by GDP

What event follows the exchange of GDP for GTP on the Gα subunit upon interaction with agonist-bound GPCR?

Dissociation of Gα-GTP subunit from the Gβγ dimer

How is the activated G-protein returned to the inactive resting state in GPCR signaling?

Hydrolysis of bound GTP to GDP

Which family of Gα proteins stimulates adenylate cyclase resulting in increased cAMP levels?

Gαs family

What is the role of Gαq/11 family of Gα proteins in GPCR signaling?

Stimulate phospholipase C-β resulting in increased IP3 & DAG levels

What are considered as key second messengers in GPCR signaling?

cAMP, IP3 and Ca2+

What does the cAMP signaling pathway involve in GPCR signaling?

Gαs-GTP activates Adenylyl Cyclase (AC) resulting in increased cAMP levels

What is the role of regulators of G-protein signaling (RGS) proteins or GTPase-accelerating proteins (GAPs) in GPCR signaling?

Accelerate hydrolysis of bound GTP to GDP in the Gα subunit

What is the composition of heterotrimeric G-proteins?

α, β, and γ subunits

What process occurs when Gαq/11-GTP activates Phospholipase C-β (PLCβ), resulting in increased IP3 & DAG levels?

Stimulation of phospholipase C-β

What is the main structural motif shared by all G-protein-coupled receptors (GPCRs)?

Seven transmembrane α-helices

What is the role of Gαq/11 family of Gα proteins in GPCR signaling?

Stimulate phospholipase C-β resulting in increased IP3 & DAG levels

What is the key function of G-protein-coupled receptors (GPCRs) in signal transduction pathways?

Modulate the activity of downstream intracellular effector proteins

What is the outcome when an agonist drug binds to its receptor, leading to the formation of a drug-receptor (D-R) complex?

Initiation of signal transduction pathways inside the cell

What is the main function of G-protein-coupled receptors in signal transduction pathways?

Mediate responses to hormones, neurotransmitters, and growth factors

What is considered as key second messengers in GPCR signaling?

cAMP, IP3, and Ca2+

What is the outcome of Gαs-GTP inhibiting Adenylyl Cyclase (AC) in GPCR signaling?

Decreased cAMP levels

What is the outcome when an agonist drug binds to its receptor in GPCR signaling?

Activation of relay proteins inside the cell

Which pathway is activated when Gαs-GTP inhibits Adenylyl Cyclase (AC), resulting in decreased cAMP levels?

cAMP signaling pathway

What is the main function of G-protein-coupled receptors (GPCRs) in signal transduction?

Activation of second messenger pathways via G-protein-coupled receptors

What is the outcome when an agonist drug binds to its receptor, leading to the formation of a drug-receptor (D-R) complex?

Cellular or biological response triggered

Which type of receptors are used by cells to convert extracellular signals into intracellular responses?

G-protein-coupled receptors

What does the cAMP signaling pathway involve in GPCR signaling?

Activation of adenylate cyclase resulting in increased cAMP levels

What is the role of Gαq/11 family of Gα proteins in GPCR signaling?

Stimulates phospholipase C-β resulting in increased IP3 & DAG levels

What is activated when Gq/11-GTP activates Phospholipase C-β (PLCβ) in GPCR signaling?

Second messenger pathways

Which major role do Gαq/11 family play in GPCR signaling?

Activation of second messenger pathways

What is the common structural motif shared by all G-protein-coupled receptors?

Seven transmembrane (7-TM) α-helices

What is the composition of heterotrimeric G-proteins?

Three protein subunits: α, β, and γ

What is the role of regulators of G-protein signaling (RGS) proteins or GTPase-accelerating proteins (GAPs) in GPCR signaling?

Slow down the hydrolysis of GTP to GDP in the Gα subunit

What is the key function of G-protein-coupled receptors (GPCRs) in signal transduction pathways?

Transducing a wide array of extracellular signals

What is the main function of G-protein-coupled receptors (GPCRs) in signal transduction pathways?

Convert extracellular signals into intracellular responses

What is the role of the Gαq/11 family of Gα proteins in GPCR signaling?

Activating Phospholipase C-β (PLCβ), resulting in increased IP3 & DAG levels

What is the main structural motif shared by all G-protein-coupled receptors (GPCRs)?

Seven transmembrane helices

What is the outcome when an agonist drug binds to its receptor, leading to the formation of a drug-receptor (D-R) complex?

Conversion of extracellular signals into intracellular responses

What is the function of heterotrimeric G-proteins in GPCR signaling?

Convert extracellular signals into intracellular responses

What does the intracellular region of a GPCR interface with?

Extracellular signaling proteins

What is activated when Gs-GTP inhibits Adenylyl Cyclase (AC) in GPCR signaling?

Decreased cAMP levels

What is considered as key second messengers in GPCR signaling?

IP3/Ca2+ and cAMP

What happens when an agonist drug binds to its receptor in GPCR signaling?

Activation of cytoplasmic heterotrimeric G-proteins

What is the composition of heterotrimeric G-proteins?

One α subunit, one β subunit, and one γ subunit

What is the process called when a drug-receptor complex activates a series of relay proteins and produces 2nd messengers inside the cell?

Signal transduction

What is the name for a group of receptors with a similar basic molecular structure that use the same signal transduction pathway?

Receptor superfamily

How many major signal transduction pathways are activated by G-protein-coupled receptors?

4

What is the key structural motif shared by all G-protein-coupled receptors?

Seven transmembrane (7-TM) α-helices

What is the main function of G-protein-coupled receptors in signal transduction pathways?

To convert extracellular signals into intracellular responses

What is the common structural motif shared by all G-protein-coupled receptors?

Seven transmembrane (7-TM) α-helices

What is the outcome when an agonist drug binds to its receptor, leading to the formation of a drug-receptor (D-R) complex?

Conformational change

What is the composition of heterotrimeric G-proteins?

α, β, and γ subunits

What is the role of Gαq/11 family of Gα proteins in GPCR signaling?

Stimulates phospholipase C-β resulting in increased IP3 & DAG levels

What is the role of the Gα subunit in the resting state of heterotrimeric G-proteins?

Harbors a guanine nucleotide-binding site

What is the key function of G-protein-coupled receptors (GPCRs) in signal transduction?

To regulate virtually every aspect of physiology

What event follows the exchange of GDP for GTP on the Gα subunit upon interaction with agonist-bound GPCR?

Activation of downstream effector proteins

What is the main function of G-protein-coupled receptors (GPCRs) in signal transduction?

Transmitting extracellular signals into the cell

What is the composition of heterotrimeric G-proteins?

2 different protein subunits: α, β, and γ

What is activated when Gαs-GTP inhibits Adenylyl Cyclase (AC) in GPCR signaling?

Decreased cAMP levels

What process occurs when Gαq/11-GTP activates Phospholipase C-β (PLCβ), resulting in increased IP3 & DAG levels?

Increased IP3 & DAG levels

What is the main structural motif shared by all G-protein-coupled receptors (GPCRs)?

Seven transmembrane (7-TM) α-helices

What is the key role of Regulators of G-protein signaling (RGS) proteins or GTPase-accelerating proteins (GAPs) in GPCR signaling?

Accelerating the GTP hydrolysis on the Gα subunit

What is considered as a key second messenger in GPCR signaling?

cAMP and IP3/Ca2+

What is the outcome when an agonist drug binds to its receptor in GPCR signaling?

Formation of a drug-receptor (D-R) complex

What happens when an agonist drug binds to its receptor in GPCR signaling?

Activation of cytoplasmic heterotrimeric G-proteins

What is the role of GPCRs in the actions of neurotransmitters & hormones?

Mediating responses to neurotransmitters & hormones

What is the key feature of GPCRs in signal transduction pathways?

Interaction with heterotrimeric GTP-binding proteins (or G-proteins)

How many Gα, Gβ, and Gγ subunits/isoforms have been identified in the human genome?

21 Gα, 5 Gβ, and 12 Gγ subunits/isoforms

What is the composition of heterotrimeric G-proteins?

3 different protein subunits: α, β, and γ

Where is the nucleotide-binding site located in the Gα subunit of heterotrimeric G-proteins?

Between the Ras-like domain and an α-helical domain

What is the outcome of GPCR interaction with agonist-bound GPCR?

Exchange of GDP for GTP on the Gα subunit

What is the role of Gαs family of Gα proteins in GPCR signaling?

Stimulate adenylate cyclase, leading to increased cAMP levels

What is the key second messenger involved in the cAMP signaling pathway in GPCR signaling?

cAMP

What is the outcome of Gαi/o-GTP in GPCR signaling?

Inhibit adenylate cyclase, leading to decreased cAMP levels

What is the main function of G-protein-coupled receptors in GPCR signaling?

Translate agonist-GPCR binding into modulation of activity of downstream intracellular effector proteins

Which Gα family stimulates phospholipase C-β, resulting in increased IP3 & DAG levels?

Gαq/11 family

What is the process called when an agonist drug binds to its receptor and triggers a chain of biochemical processes inside the cell?

Signal transduction

What is the main structural motif shared by all G-protein-coupled receptors (GPCRs)?

Interaction with heterotrimeric GTP-binding proteins (or G-proteins)

Study Notes

G-Protein-Coupled Receptors (GPCRs)

  • GPCRs are not involved in the actions of neurotransmitters and hormones.
  • GPCRs constitute the largest receptor superfamily in humans, with approximately 800 members.
  • GPCRs are involved in mediating responses to hormones, neurotransmitters, and growth factors.

Signal Transduction Pathways

  • Signal transduction involves the activation of relay proteins and production of second messengers inside the cell.
  • There are 4 major signal transduction pathways, including activation of receptor-ion channels.
  • GPCRs are used by cells to convert extracellular signals into intracellular responses.

GPCR Structure and Function

  • All GPCRs share a common structural motif of seven transmembrane (7-TM) α-helices.
  • The extracellular region of a GPCR modulates ligand access to the binding site on the receptor.
  • The intracellular region of a GPCR interfaces with extracellular signaling proteins.

Heterotrimeric G-Proteins

  • Heterotrimeric G-proteins are composed of 3 different protein subunits: α, β, and γ.
  • The Gα subunit harbors a guanine nucleotide-binding site, which is occupied by GTP in the inactive resting (off) state.
  • The N-terminus of Gα is myristoylated or palmitoylated, which results in the attachment of the G protein to the nucleus.

G-Protein Signaling

  • G-protein signaling via heterotrimeric G-proteins translates agonist-GPCR binding into modulation of activity of downstream extracellular effector proteins.
  • Gα proteins are grouped into 4 families based on their peptide sequence and functional similarities: Gαs, Gαi, Gαq/11, and Gα12/13.
  • Gαi family stimulates adenylate cyclase resulting in increased cAMP levels.
  • Gαq/11 family stimulates phospholipase C-β resulting in increased IP3 and DAG levels.

Second Messengers

  • cAMP and IP3/Ca2+ are considered key second messengers in GPCR signaling.
  • The cAMP signaling pathway involves the activation of adenylate cyclase.
  • The Inositol 1,4,5-trisphosphate/calcium signaling pathway is activated when Gαq/11-GTP activates Phospholipase C-β (PLCβ), resulting in increased IP3 and DAG levels.

Regulation of G-Protein Signaling

  • Regulators of G-protein signaling (RGS) proteins or GTPase-accelerating proteins (GAPs) slow down the hydrolysis of GTP to GDP in the Gα subunit.
  • RGS proteins or GAPs are involved in the regulation of G-protein signaling, returning the activated G-protein to the inactive resting state.

Test your knowledge of signal transduction and receptor superfamilies, specifically focusing on G-Protein-Coupled Receptors (GPCRs) in the context of the MPharm Programme. This quiz covers the key steps in receptor signaling, signal transduction pathways, the structure and function of GPCRs, and the structure and role of G-proteins in GPCR signaling.

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