Cell Signaling Pathways: DAG and Gαq Signaling

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Questions and Answers

What is the first stage of cell signalling?

Transduction

Signal amplification

Activation of cellular responses

Reception (correct)

What is the role of kinases in signal transduction?

To inhibit signal transduction

To catalyse multiple reactions each (correct)

To decrease the signal strength

To block receptor activation

Which type of receptors trigger kinase cascades?

Ligand-gated ion channels

Steroid hormone receptors

Tyrosine kinase receptors

G protein coupled receptors (GPCRs) (correct)

What is required for smooth muscle contraction?

Calcium and ATP Signup and view all the answers

Where are smooth muscles found in the body?

Throughout the body, including arteries, veins, bronchi, bladder, and more Signup and view all the answers

What happens to the receptor protein during reception?

It changes shape to transmit information Signup and view all the answers

What is the role of myosin fibres in smooth muscle contraction?

They slide past actin fibres during contraction Signup and view all the answers

What is the last stage of cell signalling?

Activation of cellular responses Signup and view all the answers

What is the result of the activation of Gαq coupled receptors in smooth muscle?

Increased cytoplasmic calcium Signup and view all the answers

What is the role of calmodulin in smooth muscle contraction?

Activating myosin light chain kinase Signup and view all the answers

What is the effect of noradrenaline on the iris radial muscle?

Contraction of the radial muscle, resulting in pupillary dilation Signup and view all the answers

What is the effect of pilocarpine on the iris sphincter smooth muscle?

Contraction of the sphincter muscle, resulting in pupillary constriction Signup and view all the answers

What is the role of IP3 in smooth muscle contraction?

Releasing calcium from the sarcoplasmic reticulum Signup and view all the answers

What is the result of myosin light chain kinase activity in smooth muscle?

Contraction of smooth muscle Signup and view all the answers

What is the role of DAG in smooth muscle contraction?

Activating protein kinase C Signup and view all the answers

What is the effect of tropicamide on the iris sphincter smooth muscle?

Relaxation of the sphincter muscle, resulting in pupillary dilation Signup and view all the answers

What happens to Gαs when GDP dissociates?

It binds to GTP Signup and view all the answers

What is the effect of Gαi-coupled GPCRs on Adenylate cyclase?

It inhibits Adenylate cyclase Signup and view all the answers

What is the result of PKA catalyzing the transfer of phosphate to myosin light chain kinase?

Prevention of phosphorylation of myosin light chain Signup and view all the answers

What is the effect of acetylcholine activation of the M3 muscarinic receptor on bronchial smooth muscle?

Contraction and narrowing of airways Signup and view all the answers

What is the result of nitric oxide binding to soluble guanylyl cyclase in smooth muscle cells?

Conversion of GTP to cGMP Signup and view all the answers

What is the effect of adrenaline activation of the β2-adrenoceptor on bronchial smooth muscle?

Relaxation and widening of airways Signup and view all the answers

What is the role of PKA in smooth muscle relaxation?

Catalyzing the transfer of phosphate to myosin light chain kinase Signup and view all the answers

What is the effect of Gαq-coupled receptor activation on the endothelium cell?

Production of nitric oxide Signup and view all the answers

Study Notes

DAG Signaling

DAG activates enzyme PKC, while IP3 combined with ligand channel in SR, leading to gate open and increasing intracellular calcium.
Increased intracellular calcium combines with calmodulin to form complexes, activating MLCK and phosphorylating myosin light chains, generating ATPase activity and causing muscle contraction.

Gαq Signaling

Activating Gαq-coupled receptors leads to increased cytoplasmic calcium, released by IP3 ligand-gated ion channels on the SR membrane.
Examples: Parasympathetic innervation of the sphincter muscle (M3 muscarinic receptor), sympathetic innervation of the radial muscle (α1-adrenoceptor).

Gαs Signaling

Agonists bind to Gαs-coupled receptors, leading to conformational change, activating adenylate cyclase, and producing cAMP from ATP.
cAMP activates PKA, which leads to muscle relaxation through two mechanisms:
- PKA catalyzes the transfer of phosphate to the phosphatase enzyme, activating dephosphorylation of myosin light chain.
- PKA catalyzes the transfer of phosphate to myosin light chain kinase, preventing phosphorylation of myosin light chain.

Cell Signaling

Three stages of cell signaling: reception, transduction, and activation of cellular responses.
Reception: agonist binds to receptor, transmitting information from extracellular to intracellular environment.
Transduction: agonist-induced conformational change in receptor initiates the process, leading to amplification of the signal through enzyme cascades.

Smooth Muscle

Found in various parts of the body, including arteries, veins, bronchi, bladder, iris, urethra, prostate, skin, uterus, and gastrointestinal tract.
Contraction: actin fibers are pulled and slide past myosin fibers, requiring ATP and calcium.
Relaxation: regulated by Gαs and Gαq signaling pathways, as well as nitric oxide.

Nitric Oxide Signaling

Activation of Gαq-coupled receptor on endothelium cell results in production of nitric oxide (NO).
NO binds to soluble guanylyl cyclase (GC), inducing a conformational change and activating the enzyme, converting GTP to cGMP, leading to smooth muscle relaxation.

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Description

Learn about the signaling pathways of DAG and Gαq, including the activation of enzymes, release of calcium ions, and muscle contraction.