White - Cell Communication 1 Flashcards
Signal Transduction
Cell-to-cell communication; must traverse from outside the cell to inside the cell; important in the development of an organism and for coordination of metabolism; absolutely required for multicellular organisms
Fast Response
Change in activity or function of enzymes or proteins in the cell
Slow Response
Change in amounts of proteins by change in expression of genes
Signal Transduction Process
Ligand binds to high affinity receptor, which produces intracellular signal proteins to interact with effector proteins; these effector proteins can alter metabolism, alter gene expression, or alter the shape and/or movement of the cell
Endocrine Signaling
Long distance signaling; signal goes to blood stream and travels to distant target cells; long lasting because it takes time to go through the circulatory system to find a target cell
Paracrine Signaling
Acts locally and affects nearby cells; short lived signals
Synaptic Signaling
Acts locally and affects nearby cells; short lived signals (specifically neurotransmitters)
Autocrine Signaling
Cells respond to signals that they themselves release or release to cells of the same type; cell secretes signal that feeds back and binds to a receptor on its own surface (growth factors); causes cells to grow, divide, and mature
Direct Cell Signaling
Immune cells; Antigen presenting cells to T-cells
Signals (Ligands)
Typically secreted by exocytosis and can stay near or far
Receptors
Bind specifically to signal molecules with high affinity (signals are produced in low levels)
Effectors
Targets of receptors inside cells: alter activity of many different proteins and generate 2nd messengers (small diffusible molecules like cAMP and Ca2+)
Nitric Oxide signaling is an example of what kind of signaling?
Paracrine signaling
Cell Surface Receptors
External domain binds ligand, transmembrane domain anchors receptor, cytoplasmic domain initiates signal by change in conformation
Intracellular Receptors
Steroid receptor can have receptor in cytosol (estrogen); alters gene expression in nucleus
G Protein Coupled Receptors
Part of 2nd messenger system; has 3 parts (Extracellular domain, transmembrane domain, cytoplasmic domain); 7 transmembrane domains
Extracellular Domain of GPCR
Binds to ligand
Transmembrane Domain of GPCR
Anchors receptor
Cytoplasmic Domain of GPCR
Associates with G-protein
G-Proteins
Heterotrimeric proteins composed of 3 subunits (alpha, beta, gamma); impacts effector; also called guanine nucleotide-binding proteins
GPCR Activity/Process
GPCR–> Trimeric G protein–> Effector enzyme–> 2nd messenger–> Targets of 2nd messenger–> Biological response
Steps in G-Protein Relaying Signals
- Ligand binds to receptor
- Conformational change occurs in receptor
- Receptor binds to G protein
- Receptor acts as a Guanidine Exchange Factor (GEF)
- Confirmation of G-alpha protein is changed such that it kicks out GDP and GTP binds to it
- G-alpha now becomes active and can bind to effector molecule and activate effector molecule
- Effector molecule in this case is adenylyl cyclase which catalyzes formation of cAMP
How do you stop the G protein from relaying signals?
Hydrolyze GTP to GDP which returns G-alpha to inactive step to be recycled through process again
What does adenylyl cyclase do?
Generates cAMP which goes on to interact with it’s target proteins to cause a biological response
