Signal transduction Flashcards
Endocrine, Paracrine, Autocrine definitions
Endocrine: Production of chemical signal by one cell type that acts on cells in a distant tissue.
Paracrine: Production of chemical signal by one cell type that acts on a neighboring cell in the same tissue.
Autocrine: Production of a chemical signal by one cell type that acts on the same cell that released the signaling molecule.
4 Types of receptors
Ligand-gated ion channel proteins (ionotropic receptors)
G protein-coupled receptors
Catalytic receptors
Nuclear receptors
Ligand gated ion channels (Ionotropic Receptors)
Integral membrane proteins
Hybrid receptor/channels
Involved in signaling between electrically excitable cells
Signaling molecule itself controls the opening and closing of ion channels by binding to a site on the receptor.
Examples: Acetylcholine (ACh), serotonin, y-aminobutyric acid (GABA)
G protein-coupled receptors
active when bound to gtp
inactive when bound to gdp
Works through an intermediary to activate / inactivate a separate membrane associated enzyme / channel.
Steps:
1.) Ligand binds
2.) Config change, GTP replaces GDP
3.) GTP makes G protein dissociate from receptor
4.) a and BY subunits dissociate
5.) a-GTP interacts with E1 (adenylyl cyclase / phospholipases). BY subunit activates ion channels
6.) a-catalyzed hydrolysis of GTP to GDP inactivates a and promotes reassembly of trimer.
E1 Enzymes and what they do.
Adenylyl cyclase
Phosphodiesterase
Phospholipases
Adenylyl cyclase: ATP -> cAMP (create cyclic compound)
Phosphodiesterase: cGMP -> GMP (break cyclic compound)
Phospholipases: PIP2 -> DAG + IP3
IP3 reacts with ER receptor, allows Ca2+ release into cytosol.
DAG activates protein kinase C
How is calcium activated/ used inside of a cell?
calmodulin (CaM) One molecule of CaM cooperatively binds 4 calcium ions. Allows to bind to other proteins.
Ca2+-CaM complex binds to / activates CaM kinases. These phosphorylate serine / threonine.
Important CaM kinase = Myosin light chain kinase (MLCK)
3 Major pathways can convert AA into eicosanoids
1st: Cyclooxygenase (COX)-> thromboxanes, prostaglandins, prostacyclins.
2nd: 5-lipoxygenase -> leukotrienes
3rd: epoxygenase
Direct pathway in making arachidonic acid
1.) cleave off c2 of arachidonic acid via PLA2.
Indirect pathway
1.) Phospholipase 2 cleaves off IP3. DAG left. (DAG is the tail for arachidonic acid)
2.) DAG lipase cuts DAG to make arachidonic acid.
Natriuresis
Enhance Na+ excretion into urine.
increased cGMP causes:
- relaxation of vascular smooth muscle to dilate blood vessels
- enhanced sodium excretion in the urine (natriuresis)
Receptor for Nitric Oxide (NO)
soluble guanylyl cyclase (inside the cell)
NO plays important role in control of blood flow / blood pressure.
Receptor Guanylyl Cyclase
GTP -> cGMP
Ligand: ANP. When ANP binds to this, relaxation / natriuresis occurs.
NOS
In vascular endothelial cells
NOS: arginine -> citrulline + NO.
In smooth muscle, NO stimulates soluble guanylyl cyclase, converts GTP to cGMP.
