Signaling #6 Flashcards
What are the beta gamma subunits of the Gi trimeric G-protein associated with?
Regulating channel activity using inward rectifying potassium channels (GIRKs)
The beta gamma subunits can modulate various ion channels and signaling pathways.
How can photons of light affect GPCRs in rod cells?
Activate the G transducin linked GPCRs to help us see in dim light
This mechanism is crucial for vision under low light conditions.
What is Optogenetics?
A technique to excite or inhibit neurons with opsins
Optogenetics has potential therapeutic applications in various pathologies.
What signaling pathways are associated with Gq-linked GPCRs?
Phospholipase C (PLC) signaling and PIP2 signaling pathways
These pathways are integral in various cellular processes.
What does IP3 receptor activity regulate?
Calcium release from intracellular stores
This is important for various cellular functions, including muscle contraction and neurotransmitter release.
What role does calmodulin play in calcium signaling?
Decoding transient rises in calcium concentrations
Calmodulin acts as a multipurpose switch protein in various signaling pathways.
What are the two signaling molecules generated by the cleavage of PIP2?
Diacylglycerol (DAG) and inositol tri phosphate (IP3)
These molecules are crucial for downstream signaling events.
Which G-protein activates Phospholipase C beta (PLCβ)?
Gq
Gq is involved in many signaling pathways that regulate cellular responses.
What activates protein kinase C (PKC)?
Interaction with DAG and calcium
PKC is involved in cell growth and differentiation signaling pathways.
What happens to IP3 after it is generated?
It diffuses through the cytosol and opens channels in the ER, releasing Ca++ into the cytosol
This is a key step in calcium signaling pathways.
What is the effect of high cytosolic Ca++ on IP3 receptors?
Inhibitory
High levels of calcium can inhibit the activity of IP3 receptors, demonstrating a feedback mechanism.
What is the resting concentration of calcium in the cytosol?
50-100 nM
This low concentration is critical for maintaining cellular homeostasis.
What are the primary agonists for IP3 receptors?
Ca2+ and IP3
Both molecules are essential for the activation of IP3 receptors.
What is the role of calcium in the activation of calmodulin?
Calcium binding induces a conformational change in calmodulin
This change exposes hydrophobic residues that interact with target proteins.
What enzymes can be activated by CaM (calmodulin)?
Kinases, nitric oxide synthase, adenylyl cyclases, phosphodiesterases, ion channels
These enzymes play various roles in cellular signaling and function.
What is the function of nitric oxide (NO) in muscle relaxation?
Stimulates a cGMP-dependent protein kinase (PKG)
PKG activates myosin light chain phosphatase, leading to smooth muscle relaxation.
Fill in the blank: Phospholipase C (PLC) is activated by the G-protein ______.
Gq
PLC plays a crucial role in various signaling pathways linked to GPCRs.
True or False: The binding of Ca2+ to IP3 receptors is stimulatory at all concentrations.
False
The effect of Ca2+ is bimodal, being stimulatory at low levels and inhibitory at high concentrations.
What does NO stimulate in the smooth muscle relaxation process?
cGMP-dependent protein kinase (PKG)
PKG activates myosin light chain phosphatase.
What is the role of myosin light chain phosphatase?
Dephosphorylates myosin light chains
This action leads to smooth muscle relaxation.
What regulates the enzyme NOS?
ca++/calmodulin
NOS stands for Nitric Oxide Synthase.
What is the half-life of NO?
~20-30 seconds
What type of receptor is the NO receptor?
Guanylyl cyclase
Fill in the blank: NO activates _______ which leads to muscle relaxation.
myosin light chain phosphatase
True or False: NO has a long half-life in the body.
False
What enzyme does PKG activate?
Myosin light chain phosphatase
How does the activation of myosin light chain phosphatase affect smooth muscle?
Leads to relaxation
