KANDPAL Q's [Intro: Signal Transduction] & [GPCR, Enzyme Linked Receptors, and Human Cancers] Flashcards
signal transduction
communication bw environment and cell/between 2 cells
T/F signal output depends on extracellular signal molecules, and molecules that respond to signals
TRUE
4 types of signal transduction
- contact-dependnent (development/immune response)
- paracrine (neighboring cells)
- synaptic (specific target)
- endocrine (whole organism)
autocrine signaling:
signals secreted by the cell bind to self to reinforce _____, particularly during _____.
developmental decisions; differentiation
the _____ of the receptors by signal molecules determines the behavior of the cells.
differential occupancy
effect of acetylcholine on a heart muscle cell
decreased rate and force of contraction
effect of acetylcholine on a skeletal muscle cell
contraction
effect of acetylcholine on a salivary gland cell
secretion
acetylcholine receptor on cardiac muscle
G-protein coupled receptor
acetylcholine receptor on skeletal muscle
ligand gated Na+ channel
acetylcholine receptor on salivary gland
G-protein coupled receptor
what is different bw the acetylcholine receptors on the cardiac muscle and on the salivary gland?
intracellular signaling proteins
T/F most signal molecules are hydrophilic
TRUE
what is the physiological consequence of acetylcholine?
smooth muscle relaxation
acetyl choline effects are mediated indirectly by _____ of NO synthase and formation of _____
activation; nitric oxide (NO)
eNOS
NOS in endothelial cells
nNOS
NOS in nerve cells
_____ make iNOS
macrophages
are iNOS inducible?
yes
when are iNOS made?
only in response to infection
phosphodiesterase (PDE)
converts cyclic nucleotide into nucleotide monophosphate
where is PDE3 expressed?
in cardiac cells
where is PDE5 expressed?
in expandable erectile tissue
where is PDE6 expressed?
in retina
inhibition of PDE will lead to _____ of cyclic nucleotides
accumulation
dynamite is an explosion of _____
prone nitroglycerine
name the 6 hydrophobic signals mentioned in class
cortisol estradiol testosterone vitamin D3 thyroxine retinoic acid
nitric oxide, a ____ molecule that readily passes throughout the membrane, mediates a variety of cellular changes that have been targeted by drugs used to treat _____ and _____.
small
angina
erectile dysfunction
what synthesizes NO?
NOS
T/F NOS, which synthesizes NO, also exists as various isoenzymes in tissues
TRUE
soem signals result in a response within seconds to minutes and others take minutes to hours depending on _____ or _____
modification of existing proteins OR synthesis of new proteins
nuclear receptors that recognize steroid hormone have a _____ and a _____
DNA binding domain AND ligand binding domain
G-Protein Coupled Receptor (GPCR) = _____ + _____
Receptor + G-Protein
how many transmembrane domains do GPCR have?
7
what are the ligands for GPCR?
- hormones
- NTs (proteins, peptides, aa derivatives, fatty acids)
- photon
- H+
- Ca2+
what are the 2 similar structures that all GPCRs have?
seven pass & serpentine receptors
N-terminus of GPCR is _____, whereas C-terminus is _____
extracellular; intracellular
what do GPCR bind?
heterotrimeric G-proteins
a G-protein is activated by disassembly of _____, _____, and _____
alpha, beta, gamma
which part of the G-protein is the GTPase?
alpha
_____ alpha of the G-proteinactivates its target proteins
active
_____ bound alpha of G-protein is active
GTP
what controls the activity of alpha subunit of G-protien?
RGS (Regulator of G-protein Signaling) proteins
RGS proteins act as alpha subunit specific ____
GAPs (GTPase Activator Proteins)
heterotrimeric G-proteins are classified into 4 categories based on their _____
downstream effects
Gs
- stimulatory G-protein
- active alpha subunit (GTP bound) activates adenylyl cyclase
Gi
- inhibitory G-protein
- active alpha subunit (GTP bound) inhibits adenylyl cyclase
Gq
modulate phospholipase C (PLC) activity
G12/13
involved in cytoskeleton reorganization and oncogenesis
what does cAMP do?
activates protein kinase A (PKA)
cAMP can also bind to certain channels for their activation. For example, _____, which is a _____ channel
CFTR (cystic fibrosis transmembrane conductance regulator); chloride channel
what are the 2 subunits of PKA?
regulatory subunit and inactive catalytic subunit
cAMP binds to which subunit of PKA?
regulatory subunit
T/F phosphatidylinositol 4,5 bihosphate (PIP2) is found in inner half of plasma membrane
TRUE
what converts PIP2 into IP3?
PLC-beta (phospholipase C-beta)
cholera toxin
it modifies the alpha subunit of Gs-protein. by ADP-ribosylating the GTP bound alpha of the Gs-protein, the alpha remains active. as a consequence, adenylate cyclase is active. cAMP level rise. CFTR remains continuously activated. efflux of Cl- and water into the gut. diarrhea and vomiting
what does pertusis toxin (whooping cough) do?
it modifies GDP-bound alpha subunit of Gi-protein. modified alpha can’t be activated by exchange of GDP for GTP. alpha remains inactive. Gi can’t do its job so adenylate cyclase cannot be inhibited. levels of cAMP remain elevated. CFTR activated.
what is the fastest G-protein mediated responses known in vertebrates?
visual transduction
visual transduction: receptor activation leads to fall in _____ levels
cGMP
cGMP gated _____ channels open in (light/dark?) when cGMP levels are high
Na+; dark
_____ activated rhodopsin activates _____ that in turn activates _____. this results in low cGMP level. Na + channels close. synaptic signaling inhibited as a result.
light; transducer (Gt); cGMP phosphodiesterase