MCM 2-5 Signaling I Flashcards
Ligands bind to receptors via what type of interaction?
what effect can this binding have on the receptor?
ligands bind receptors non-covalently which allows for interaction to be reversible
this binding can induce a conformation change in the receptor which can change its activity or affinity for another molecule
if the ligand binds a receptor on the outside of the cell….
secondary messengers will carry the message through the cell.
These allow for signal relay and subsequent amplification
benefits of secondary messengers?
allow for signal relay and subsequent amplification
amplification of signals allows for
- smaller number of receptors and signal molecules to be needed.
- shorter response time
steps leading up to signal transduction
- ligand receptor binds
- signal is amplified by secondary messenger
- amplification causes the signal to be transduced more quickly
the activation of a single receptor can lead to
the activation of a single receptor can lead to
formation of MANY secondary messenger molecules —> multiple coordinated responses or a single/amplified response.
what will generally cause the signal to be stronger?
greater concentration of signal molecules and greater density of receptors
what factors contribute to the exact reactions observed with individual receptors and their ligands?
signal molecule half life and receptor affinity for ligand
short half life means the molecule may need to be synthesized at a faster rate to adequately interact with receptor
if receptor affinity is low, the ligand again may need to be produced more rapidly for sufficient interaction to occur
signal molecule concentration is controleld by
how fast molecule is produced and degraded
typically degredation rate is constant, but synthesis rate can vary
fast synthesis + fast degredation
strong signal
slow synthesis + fast degredation
weak signal
degredation speed of hormones
hormones are degraded slowly, signal takes a long time to decrease. hormones are long acting signals
if there are more receptors…
there are more spots for ligand to bind and illicit response
if a receptor has a higher affinity than another…
it will take less ligand to bind it
if a cell is being repeatedly exposed, it will show ______
adaptation via desensitizing receptors, degrading receptors, or regulating receptor synthesis
how do nuclear receptors regulate gene expression
nuclear receptors are intracellular receptors that bind steroid hormones
once hormone binds, inhibitor released and the DNA binding domain of the receptor is exposed, allowing for regulation of genes with matching promoter sequences
some genes will require addiitonal parter TF to be activated. Therefor, the partner TF that a cell produces will determine the genes that will be affected by a given signalling pathway.
signals may pass from ________, but ussually come from ________. example?
cell to cell directly (gap), but ussually come from outside of the cell, like in the endocrine system.
describe the signaling molecules and receptors of endocrine system
very low concentration signals, requiring high affinity receptors
describe the signaling molecules and receptors of neurotransmitter systems
very high concentration signals (neurotransmitters), with very low affinity receptors on post-synaptic cells
rank the affinity of receptors in the neurotranmitter, paracrine, and endocrine systems
highest affinity - endocrine
medium affinity - paracrine
lowest affinity - neurotransmitters (due to high levels of NT released)
steroid hormones must be able to…
diffuse across the membrane
affinity
the strength with which a receptor will bind its ligand
half-life
the amount of time it takes for the body to halve the amount of a particular signal molecule in circulation
adaptation
process of changing a cellular response to a signal of constant concentration (like reducing receptor density/affinity)
autocrine
cell secretes signal taken up by receptor on same cell
paracrine
cell secretes signal taken up by neighboring cell
synaptic
signal processing specific to nerve cells and postsynaptic cells. NT secreted by nerve cell, travels across synaptic cleft, taken up by receptors on post-synaptic cell
high concentration signal, low affinity receptor
endocrine
cell secretes signal into blood stream to be distributed systemically.
- very low concentration signal
- very high affinity receptor
ligand gated
membrane protein channel that opens in response to binding a ligand. can be on cytosolic or extracellular side of membrane
primary response gene
genes activated by intracellular signals from a hormone-occupied receptor. hormone turns these genes on
eicosinoid
hydrophobic signal subclass, made by fatty acids that bind surface receptors rather than cytoplasmic proteins
(steroid hormones all work by binding cytoplasmic proteins to be taken into the cell).
Describe the similarities and differences between sensory, paracrine, endocrine, and synaptic signaling.
All involve extracellular molecules binding to cellular receptors. Sensory signals originate outside the organism, endocrine originate in one part of the body and move through the bloodstream to another part, paracrine signals travel within a tissue, and synaptic signals only travel across the synaptic cleft.
Sensitivity of a cell to ligands can be decreased after prolonged exposure. What is this process called, and what mechanisms may be involved?
This process is called adaptation and it may involve changes in gene expression, receptor turnover, or second messenger systems.
Aspirin and other anti-inflammatory drugs block signaling of some members of the ____________ family of signaling molecules. What kind of receptors (cell surface or intracellular) do they bind to?
Aspirin is anti-inflammatory and blocs eicosinoid signaling, which is important in many inflammation responses.
Explain the role of heterodimer formation in steroid hormone signaling and its importance for determining the different responses if different tissues to the same hormone.
Heterodimeric transcription factors formed by nuclear receptors allow different cell types to respond differently to the same steroid hormone, because each cell type can express a different partner to make a different heterodimer and potentially elicit different responses.
