SIGNAL I & II Flashcards
Where do Neurocrine signals originate?
Nervous system
Where do Endocrine signals originate
Distant sites
Where do Paracrine signals originate
Nearby Cells
Where do Autocrine signals originate
From same cell
Where do Juxtacrine signals originate
From a fixed adjacent structure
What are the 6 categories of Signaling molecules
Proteins and peptides
Amino acids/derivatives
Steroids
Eicosanoids
Gases
Attached ligands
How are cell signals recieved?
By receptors
What is a ligand?
Soluble or external signal
Where are receptors located?
- In the plasma membrane
- Most are these
- Protein, peptide, neurotransmitters
- Cytoplasm and nucleus
- Steroid/retinoid receptors.
TM Receptors: Three domain structure
What is the role of the extracellular domain (Ectodomain)
Ligand binding
What is the Function of the intracellular or cytoplasmic domain?
Contacts signal transduction system
May have intrinsic enzyme activity.
Important Characteristics of Receptors
- Specific: Binding only to their molecule
- Saturable: Only bind so many molecules of the ligand before they cannot bind any more.
- Threshold: Activity exhibits threshold
- Certain number of receptors that must be engaged before a biological response can be seen.
Examples of Endocrine cytokines?
PRL/GH
Leptin
Paracrine Cytokine examples
Interleukins
Interferons
Epo
Receptors and dimerization?
- All receptors are either
- Dimers
- Monomers that dimerize in response to ligand.
Down stream actions of cell signalling?
Cell growth, differentiation, specific tissue funtions
What are two off mechanisms of receptors?
Dephosphorylation
De novo synthesis of pathway inhibitors
Pathway transduction outline of the four players that develop a signaling cascade?
Signal -> Reciever -> Adaptor -> Effector
Important contraints to cell signaling
- Accuracy - specificty both up- and downstream
- Fidelity - Passed without diminution and often requires amplification
- Regulatable - Must have a way to turn it on and off.
Second messenger?
Is a small molecule that is generated in response to or is released in response to a ligand receptor interaction that then is able to activate the rest of the response.
Secondary messengers side functions
- Regulatory factors for other molecules
- Nearly always regulate enzymes and enzyme activators
- Very often regulate kinases and phosphatases.
Mechanism to end signal transduction?
- The signal must be turned OFF to reset cellular sensitivity to this and other signals.
- Systems that do this
- Contitutively active enzymes
- Activated by the signal pathway itself
- Feedback and feed-forward mechanisms.
- Systems that do this
