Download 3.D.4 Changes in Signal Transduction Pathways

Signal Transduction, continued
Transduction and response
When signal transduction is blocked or
defective, the effects are usually
harmful to the cell.
Example: Cholera
Some bacteria
excrete exotoxins
that interfere with
signal transduction
pathways. The
bacteria that causes
cholera is an
intestinal parasite.
Cholera toxin modifies a G-protein so that its attached
GTP cannot be hydrolyzed back into GDP.
This results in prolonged activation of intestinal cells,
which increases water efflux into the intestine.
Example:
Type II Diabetes
Mellitus can
result from
reduced kinase
activity in the
RTK activated by
insulin.
Example: Nerve agents destroy an enzyme that
degrades the neurotransmitter acetylcholine.
The buildup of acetylcholine leads to muscle
failure and ultimately results in respiratory
failure. Sarin gas, as well as some insecticides,
are nerve agents.
Example: In the autoimmune disease
Myasthenia gravis, acetylcholine receptors
are damaged by antibodies, resulting in
loss of muscle coordination.
Signal Transduction:
Transduction and Response
Transduction
• Needed to continue the message to the inside
of the cell
• Domino effect
• Original signaling molecule is NOT passed
along
• Very often, proteins change shape due to
phosphorylation
Second messengers are also often used.
Second Messengers
• Small, NON-PROTEIN, water-soluble molecules
or ions
• Most common: cAMP and calcium ions
– You will do more work with these on your own.
Your Job:
• WebQuest (cAMP, problems w/ pathways)
• Response- notes