Upload
maria-chiaffarano
View
14.288
Download
0
Embed Size (px)
Citation preview
My Dog is Broken!Maria Chiaffarano and Julia Burton
Signal Transduction Process by which an extracellular signal
molecule activates a membrane receptor that in turn alters intracellular molecules to create a response
Transmembrane receptors span the cell membrane (part of the membrane is inside, part is outside the cell)
A chemical signal binds to the extracellular part of the receptor causing a conformational change in the receptor (shape change)
Signal Transduction (cont) The conformational change in the
receptor also changes the part of the enzyme inside the cell
There is a cascade of signals within the cell once activated
With each step, the signal is amplified, a small signal can lead to a large response
The signal causes a change in the cell
Email 1
Email 1 (cont) Nitric Oxide is the first messenger and binds to the
extracellular domain of the receptor Guanylyl Cyclase is the second messenger inside
the cell. The Nitric Oxide enters the cell and activates the messenger. The input of GTP makes cyclic GMP
GMP and the addition of ATP is an input of energy into the cascade and activates PKG (protein kinase)
Activated PKG activates the Phospho-Proteins which then lowers the amount of Calcium in the blood
Email 1 (cont) The lowering of Calcium desensitizes
the cell to Calcium and increases blood flow
Increased blow flow leads to relaxation The arrows in this diagram become
increasingly larger because cell signals are amplified throughout the cell so that a small signal can trigger a large response
Email 1 (cont) The receptor in this cell is an enzyme-
linked receptor Has two important domains
Intracellular Extracellular
Email 2
Email 2 Ginseng
Ginseng is shown to increase locally produced nitric oxide (NO), all over the body. The mechanism is not completely understood, but the outcome is enhancement of erection in males.
Viagra Muscle relaxation is countered by the activity of
PDE breaking down cGMP. Viagra increases erection by blocking the activity of the PDE; by slowing the break-down of cGMP, erection is enhanced.
Email 2 (cont) Ginseng is known to increase NO2 If Ginseng was used for the dog, the
amount of NO2 would be in greater supply. More NO2 would enter the cell and trigger the cell signal and response
Ginseng would increase blood flow by increasing the signal
Email 2 (cont) Phosphodiesterase (PDE5) is any enzyme that
breaks a phosphodiester bond It functions to remove cGMP once a signaling
molecule, such as nitric oxide, is no longer present
This turns off the function of the signal molecule Viagra inhibits phosphodiesterase so that it does
not get turned off This leads to increased blood flow and relaxation
Email 2 (cont) If neither chemical works, PKG is suspected to be
dysfunctional PKG activates the proteins and the lowering of
calcium; it is activated by the cGMP PKG affects other parts of the “cascade” in the cell
IP3 P Lamban Myosin light chain phosphotase
Email 2 (cont) Inositol trisphosphate receptor (IP3)
Membrane glycoprotein complex that acts as a calcium channel
When activated, it releases calcium into the cytoplasm
If PKG is dysfunctional, too much calcium will be released which would then raise calcium levels and decrease blood flow
Email 2 (cont) Phospholamban (P Lamban)
52-amino acid integral membrane protein that regulates the Ca2+ pump in cardiac muscle and skeletal muscle cells
Cardiac muscle is also smooth muscle (same as the muscle in this case study)
If PKG is dysfunctional, it will not be able to control P Lamban. Therefore, the calcium pumps would not work properly and create a build up of calcium
Email 2 (cont) Myosin-light-chain phosphotase is an
enzyme that catalyzes a chemical reaction It is important for regulating contraction in
smooth muscle It is inhibited by calcium pathways for
maintaining muscle contraction If PKG is not working properly, the myosin
light chain will contain too much calcium and muscle contraction will not function properly