Lecture 8: Cell Signaling Flashcards
What are the three main steps of Cell Signaling?
Reception
Transduction
Response
Why do cells communicate?
Cells need to respond as a cell and as part of a whole tissue, reacting to signals from other cells and the environment, which can be chemical or other forms like light, taste, and smell.
What are the features of local signaling?
Local signaling involves signals acting on nearby target cells, such as paracrine signaling (e.g., growth factors like fibroblast growth factor) and synaptic signaling (e.g., neurotransmitters like acetylcholine).
What are examples of local signaling?
- growth factors such as fibroblast growth factor – FGF1 (paracrine)
- Neurotransmitters such as acetylcholine – ACh (synaptic)
- Can act on the signaling cell (autocrine)
What is long distance signaling?
Long-distance signaling occurs when hormones secreted from endocrine cells travel via the circulatory system to act on target cells, such as insulin secreted from pancreatic beta cells.
What are the 3 steps to cell signaling?
Reception
Transduction
Response
What are the names for the Signaling Molecule?
Ligand
First Messenger
Primary Messenger
What is Reception?
Signaling protein (otherwise called primary messenger or ligand) binds to a receptor protein causing a change in shape of the receptor protein
What is Transduction?
The altered receptor protein activates another protein (eg G-protein). The activated protein may cause a relay of changes causing other proteins to be activated.
Each activated protein causes a series of changes - often via phosphorylation.
What is Response?
All activated proteins cause a certain function or functions to occur in the cell
What is a TARGET receptor?
It’s the receptor with the complementary shape to the shape of the ligand - structure determines function
Is the type of cell receptors specific to the type of the cell?
No, there may be different receptor molecules on the cell surface membrane of one cell type at different points in time
What are the two types of receptors?
Intracellular and membrane-bound/cell surface receptors
What are intracellular receptors?
Primary messenger is generally hydrophobic and small - lipid soluble.
What are membrane bound / cell surface receptors?
Primary messenger is generally hydrophilic and/or large
examples include GPCR (G protein coupled receptor) and ligand-gated ion channels
What is a GPCR?
Transmembrane Proteins
Pass the Plasma Membrane seven times
Hundreds of different GPCRs exist
Many different ligands
G-protein coupled receptors are transmembrane proteins that pass through the membrane 7 times.
Its extracellular portion has ligand binding site and its inner portion has loops that interact with G proteins.
It is the target for 1/3 of all modern drugs
Where does specificity come from?
Specificity comes from the 3D molecular shape of the proteins involved, where only target receptors interact with specific signals (ligands) to activate signal transduction pathways.
Where are water-soluble molecule receptors found?
Receptors for water-soluble molecules are membrane-bound
What are examples of water-soluble molecule receptors?
G Protein Coupled Receptors, Receptor Tyrosine Kinases, and ligand-gated ion channels.
Why are water-soluble molecule receptors where they are?
Because the molecules cannot transverse the plasma membrane
Where are lipid-soluble molecule receptors found?
Receptors for lipid-soluble molecules are not membrane-bound and can be found in the cytoplasm or inside the nucleus
What are examples of lipid-soluble molecule receptors?
Receptors for hormones like testosterone and estrogen.
What are G-protein coupled receptors (GPCRs)?
GPCRs are transmembrane proteins that pass through the plasma membrane seven times, with hundreds of different GPCRs existing for diverse functions, including development and sensory reception.
What are G Proteins?
G proteins are molecular switches which are usually inactive when GDP is bound and then become switched on or active when bound to GTP (guanosine triphosphate)
