Cell Signaling I (Sept. 11 - Simmons) Flashcards
What two components are necessary to transduce a signal?
- Signaling molecule
2. Corresponding receptor
What are the types of signaling 5 general types of signaling
- Autocrine
- Paracrine
- Contact dependent
- Synaptic
- Endocrine
Describe autocine signaling
Cell secretes its own signaling factors that effects itself
Describe paracrine signaling
Cell secretes signaling molecules that affect cells with receptors only in local area
What is contact dependent signaling?
When a cell usually containing a signaling molecule in its plasma membrane docks/contacts another cell with the receptor and causes the signal to be transduced
Describe synaptic signaling
Usually at the end of axons (affecting other nerves or a target cell). Signaling molecules must diffuse into space and cross a junction in order to bind the receptor. (Neurotransmitters)
What is endocrine signaling?
Systemic signaling - usually occurs when hormones are secreted into bloodstream on a diffuse level. Slow to effect but prolonged. Affects target cells downstream
How is it that cells do not universally respond to signaling molecules the same way?
Each cell contains or may lack specific receptor domains for each signaling molecules ensuring specific responses to different molecules
Describe how cells can use multiple signaling molecules to decide what to do?
Different signaling molecules and their combinations dictates to a cell whether they should grow, divide, differentiate, or undergo apoptosis.
(additive signal transduction)
True/False: A signaling molecule may have different effects depending on the target cell
True. Acetylcholine works in different ways to produce different responses in different tissues. Multiple receptors exist for each signal
Signaling molecules which are found floating throughout the bloodstream are usually ______ and cannot _______ the cell
- hydrophilic
2. enter
Hydrophobic signaling molecules have to have this when in the blood stream…
What is a carrier protein
What is the most common type of hormone that affects nuclear receptors
Steroid hormones
How do steroid hormones work to elicit an effect in cells?
- Diffusion into cell
- Binding to steroid receptor (transcription factors)
- Activation of said transcription factor
- Induction of primary-response proteins
What are the differences between primary-reponse and secondary-response proteins?
Primary response proteins may either repress primary receptors or go on to turn secondary response genes.
Secondary response proteins are created from primary response protein signals. (referred to as delayed response to hormones)
Nuclear receptor superfamilies all have this motif in common
DNA binding domain
Nuclear signaling receptors usually have a _______ protein at C-terminus and a _______ binding domain.
- inhibitory
2. ligand
Describe what happens when a ligand binds to a nuclear receptor
-Inhibitory protein released
-Recruitment of coactivator protein
(binds transcription activating domain and ligand)
-Binding to DNA of receptor
-expression of target genes
What are the two classes of cell-surface receptors?
- Ion-coupled channels
- Enzyme-coupled receptors
How do enzyme-coupled receptors work?
Signaling molecule- in form of a dimer binds to receptors
Causes association of transmembrane receptors and either
1. Activation of their catalytic domains
OR
2. Activation of associated protein
G-protein-coupled receptors are a major part of _____ interaction. Over _____% of them bind to these receptors.
- Drug/medicine
2. 50%
Describe the critical structure of G-protein receptors
- 7 transmembrane passes
- Receptor N- terminal domain (usually found glycosylated)
- C terminal loops form phosphorylation and activation domains in cytosol
- Membrane passes arranged in a circular bundle
The three components of the G-protein are:
- alpha subunit
- beta subunit
- gamma subunit
Which subunit binds GTP? What does GTP do?
Alpha subunit - GTP activates G-protein
