Overview of Signaling Flashcards
Intracellular communication facilitates what?
signal transduction
What are the components of signal transduction?
*First messenger (Ligand)
*Receptor
*Amplifier enzymes
*Second messenger
*Amplification cascade (kinases)
Why must cells communicate with their envionments?
to maintain homeostasis (constant internal environment in response to environmental changes)
What ends the signal transduction process?
The effect
What are the types of cellular communication?
- Direct cell-to-cell communication
- Local cell-to-cell communciation
- Long distance cell-to-cell communication
What is direct cell-to-cell communication? How are messages conveyed?
Direct cytoplasmic connection
Via gap junctions
What is local cell-to-cell communication?
Signalling between cells using autocrine or paracrine signalling
What is signal amplification?
A single signal is amplified into many intracellular molecules
What are the different long distance cell-to-cell communication
- neurotransmitters
- neurohormones
- hormones
Explain activation of the signal pathway
- First messenger (Ligand)
- Receptor
- Second messenger
- Amplification cascade (kinases)
- Effect
What are some downstream effects/cell responses
*Structural effects
*Ion changes
*Metabolic effects
*Membrane changes
*Gene expression
*Cell growth (proliferation)
*Programmed cell death (apoptosis)
What is an agonist?
Activates a receptor
What is an antagonist?
Blocks receptor activity
What is a ligand?
primary molecule that activates a receptor
What is the implication of lipophilic ligands?
Direct diffusion into cell
Intracellular binding to receptor (i.e.hormones)
What is the implication of lipophobic ligands?
Transported into cell
Extracellular binding to receptor
Discuss receptors in the cytosol
*hormone binding triggers dissociation of chaperone, heat shock proteins (HSP)
*dimerizationand translocationto the nucleus
*binds to a specific sequence of DNA known as a hormone response element (HRE)
*nuclear receptor DNA complexin turn recruitsother proteins
*transcriptionof downstream DNA into mRNA
*translatedinto protein
*results in a change in cell function.
Discuss receptors in the nucelus
Steroid receptors are dimers of zinc-finger proteins that reside within the nucleus (except for the glucocorticoid receptor which resides in the cytosol until it binds its ligand).
What are the ligands of nucleus receptors
- glucocorticoids (ie. cortisol)
- mineralocorticoids (ie. aldosterone)
- sex hormones (ie. estradiol; progesterone; testosterone)
What are the mechanisms of receptors in the nucleus?
- steroid binds its receptor
- steroid-receptor-complex…
- releases the histone deacetylases(HDACs) and recruits histone acetylases(HATs) relieving chromosome repression;
- binds to a specific DNA sequence (the Steroid Response Element, SRE) in the promoters of genes it will turn on.
What are 4 different types of membrane-bound receptors?
- ligand-gated channels (ligand binding opens or closes the channel)
- receptor-enzyme (ligand binding activates an intracellular enzyme)
- G protein-coupled receptor (ligand binding opens an ion channel or alters enzyme activity)
- Integrin (ligand binding to integrin receptors alters tha cytoskeleton)
