Signaling #4 Flashcards
What is a plasmid?
A genetic structure in a cell that can replicate independently of the chromosomes.
Plasmids often contain a multiple cloning site where a sequence of DNA, typically a gene, can be inserted.
What does GFP stand for and what is its significance?
Green Fluorescence Protein; it is important for its properties in research as a fluorescent tag.
GFP is used to visualize and track biological processes in real-time.
How does fluorescence resonance energy transfer (FRET) work?
FRET measures intermolecular interactions in G Protein-Coupled Receptors (GPCR) signaling.
It indicates how long a G-protein interacts with ligand-bound GPCR.
What is the relationship between blocking β2 adrenergic receptors and PTSD?
Blocking β2 adrenergic receptors with propranolol can help with PTSD and other disorders.
This approach is based on the receptor’s role in the stress response.
What is cAMP and how does it relate to PKA activation?
cAMP is a signaling molecule that leads to PKA activation.
The generation of cAMP activates PKA, which then phosphorylates target proteins.
What are A-kinase Anchoring Proteins (AKAPs)?
Proteins that localize signaling and regulatory elements to specific regions in the cell.
AKAPs help assemble multiprotein signaling complexes.
What role do AKAPs play in cardiac muscle signaling?
AKAPs create focal points of enzyme activity that transduce intracellular actions of hormones and neurotransmitters.
They control the activity of calcium channels in cardiac muscles.
What is the effect of cholera and pertussis toxins on GPCR signaling?
They disrupt GPCR signaling and are linked to conditions like uncontrolled growth (acromegaly).
Understanding these toxins helps in studying cellular signaling pathways.
How do PKA I and PKA II differ?
PKA I is largely soluble while PKA II is tethered and associated with AKAPs.
They differ in the type of regulatory subunits that associate with catalytic subunits.
What happens to cAMP levels during stimulation of a neuron?
cAMP levels can increase from < 5 x 10^-8 M to ~ 1 x 10^-6 M within 20 seconds.
This rapid change amplifies the signal from a single ligand molecule binding to a GPCR.
What do AKAPs do in terms of signaling pathways?
AKAPs localize signaling events and target complexes to specific locations in the cell.
They act as adaptors to assemble macromolecular complexes.
What is the function of phosphodiesterase (PDE) in cAMP signaling?
PDE degrades cAMP to regulate its levels and activity in signaling pathways.
Basal PDE activity keeps cAMP levels low in the absence of ligand.
How does PKA affect PDE4D3 activity?
PKA phosphorylates PDE4D3, increasing its activity and affinity for mAKAP, leading to reduced local cAMP levels.
This creates a negative feedback loop in cardiac myocytes.
What is the role of CREB in transcription?
CREB is phosphorylated by PKA, increasing its transcriptional activity significantly.
Phosphorylated CREB recruits RNA polymerase II to promote gene transcription.
What is the significance of the KID in CREB?
KID stands for kinase-inducible domain, which binds TORC and promotes CREB dimerization.
This interaction is crucial for the recruitment of transcription machinery.
What does the term ‘scaffolding proteins’ refer to?
Scaffolding proteins, like AKAPs, provide specificity and organization to signaling pathways.
They help assemble signaling complexes and facilitate rapid responses in cells.
How does PKA link cAMP signals to transcription?
PKA activates and phosphorylates CREB, enhancing transcriptional activity by 20-30 times.
This is essential for gene expression in response to cAMP signaling.
What do p300 and CBP relax to promote transcription?
Chromatin structure at gene promoter
They have intrinsic HAT activity and recruit basal transcription machinery.
What sequence do genes regulated by cAMP contain?
CRE (cAMP response element)
This sequence indicates potential regulation by increased cAMP levels.
What critical residue in CREB is phosphorylated for transcriptional activity?
Ser-133
Phosphorylation at this site is essential for CREB’s function in transcription.
What are TORCs in relation to CREB?
Cofactors called Transducers of Regulated CREB
They work with CREB to promote transcription upon entering the nucleus.
Under resting conditions, where does TORC reside?
In the cytoplasm
It enters the nucleus upon dephosphorylation to act with CREB.
What two processes regulate TORC dephosphorylation?
- Ca2+-dependent dephosphorylation mediated by calcineurin
- PKA-dependent inhibition of SIK2
These processes are crucial for TORC’s activity.
What disease is caused by the bacterium Vibrio cholerae?
Cholera
This disease results in intense diarrhea due to fluid leakage in the intestine.
What does cholera toxin do to G proteins?
Irreversibly activates them
This results in a life-threatening loss of water and salts.
What mechanism prevents Gsα from hydrolyzing GTP in cholera?
ADP-ribosylation
This modification keeps Gsα permanently active.
What does pertussis toxin do to Giα?
Catalyzes ADP-ribosylation at a cysteine residue
This blocks the inhibitory pathway and increases cAMP production.
What is a common mechanism by which protein activity is regulated?
ADP-ribosylation
This occurs in both eukaryotes and prokaryotes.
What is the significance of the R201 residue in Gsα?
It is crucial for hydrolyzing GTP to GDP
Mutations here can lead to uncontrolled cell growth.
What condition is associated with mutations in the R201 site of Gsα?
Adenomas
These benign tumors can arise from somatic mutations affecting GTPase activity.
What receptor links to Gs in patients with gigantism or acromegaly?
Growth Hormone Releasing Hormone (GHRH) receptor
Mutations lead to hypersecretion of growth hormone.
What syndrome causes scars on bone tissue and increased function of growth-regulating glands?
McCune-Albright syndrome
20-30% of affected individuals may have acromegaly.
