Lec 2.10 Cell communication Flashcards
What is Signal Transduction?
Cell to Cell communication. Extracellular signaling molecules bind to specific receptors in target cells to initiate a chain of events.
What 2 major types of responses do external signals induce?
Fast and slow response
What happens in the fast response?
Change in activity or function of enzymes or proteins in cell
What happens in the slow response?
change in amounts of proteins by change in expression of genes.
What happens if you interrupt the signal transduction pathway for Leptin?
Over eating. Dont know youre full.
What are the 5 types of signaling?
Endocrine, Paracrine, synpatic, Autocrine, direct cell
What is endocrine signaling?
Long distance signaling. Long lasting.
What is paracrine signaling?
Acts locally at cells nearby. Short lived.
What is synaptic signaling?
Acts locally at cells nearby. Short lived.
What is an ex of synaptic signaling?
Neurotransmitters
What autocrine signaling?
Cells response to signals that they themselves released or cells that are the same type as them have released.
What is an ex of autocrine signaling?
Growth factors in cancer cells
What is direct cell signaling?
Another way of signaling.
What are two ex of direct cell signaling?
Immune cells. Presenting cells to T cells.
What are the two types of receptors?
Cells surface receptors, Intracellular receptors
Why cant most ligands or hormones get into a cell?
They are hydrophilic or large
What are the 3 parts of the G-protein-coupled receptors?
- Extracellular domain. 2. Transmembrane domain. 3. Cytoplasmic domain.
What does the extraceullular domain do in the G-protein-coupled receptors?
binds to ligand
What does the transmembrane domain do in the G-protein-coupled receptors?
anchors receptor
What does the cytoplasmic domain do in the G-protein-coupled receptors?
associates with G-protein
What are the G-proteins composed up of?
3 subunits. Alpha, Beta, gamma.
What do heterotrimeric G proteins do?
Regulate target enzymes
What are the 6 steps to signaling by Trimeric G-proteins?
- Inactive. 2. Activation of receptor by ligand binding. 3.Activated receptor binds to G-protein (acts as GEF). 4. G alpha releases GDP and binds GTP, and dissociates from G beta gamma. 5. G alpha binds and activated adenylyl cyclase. 6. G alpha hydrolyses GTP to GDP, dissociates from adenylyl cyclase and binds G beta gamma (inactive).
What is Adenylyl cyclase? What does it generate?
Effector protein. Generates cAMP.
What does cAMP do?
Goes on to interact with its target proteins to cause a biological response.
What disease deals with G proteins?
Cholera.
What does Cholera do to G proteins?
Modifies G protein by keeping the G alpha in the GTP active form forever. Thus making pathway always active. Causing diarrhea.
What does cAMP activate?
PKA
What results in an Active PKA?
Binding of 2 cAMP molecules.
What can PKA do?
Regulate proteins by adding phosphate group.
What does adding a phosphate group to a protein do (PKA)?
Adds two negative charges that change conformation of protein
What are 4 things that PKA can also do?
- Phosphate group can form part of structure that other proteins recognize. 2. Activation/inactivation of enzymatic target proteins. 3 Alteration of intracellular localization of target proteins. 4. Change abundance of target proteins
What can induce activation of PKA?
Epinephrine
Name and describe the 4 types of cell signaling.
- endocrine signaling: Long distance signaling. Long lasting. 2. Paracrine signaling: Acts locally at cells nearby. Short lived. 3. Synaptic signaling: Acts locally at cells nearby. Short lived. 4. Direct cell signaling: Immune cells. Presenting cells to T cells.
Describe the steps from binding of a ligand to a G protein coupled receptor to production of a 2nd messenger to induce an effector response.
- Inactive. 2. Activation of receptor by ligand binding. 3.Activated receptor binds to G-protein (acts as GEF). 4. G alpha releases GDP and binds GTP, and dissociates from G beta gamma. 5. G alpha binds and activated adenylyl cyclase. 6. G alpha hydrolyses GTP to GDP, dissociates from adenylyl cyclase and binds G beta gamma (inactive).
How do cyclic AMP and PKA work to bring about a response?
- Regulate proteins by adding phosphate group. 1. Phosphate group can form part of structure that other proteins recognize. 2. Activation/inactivation of enzymatic target proteins. 3 Alteration of intracellular localization of target proteins. 4. Change abundance of target proteins
Name and describe 3 ways to stop a signal in a signal transduction pathway
- Receptor sequestration: endosome invagination of memebrane. 2. Receptor destruction: endosomes + lysosomes. 3. Removal of signaling molecule: phospohodiesterases will remove cAMP.
