Cellular Signaling II Flashcards
epinephrine signaling results in
production of glucose-1-phosphate, which can readily be converted to glucose and released into the bloodstream.
Protein kinase A
is activated by cAMP when the latter binds to the regulatory subunits of the enzyme, causing them to be released from the catalytic subunits.
Kinases
enzyme that put phosphates on things
Phosphatases
enzyme that remove phosphates from things.
phosphodiesterase.
breaking down cAMP with an enzyme. Turns off signal. Breakdown of cAMP by phosphodiesterase has the effect of inactivating protein kinase A.
Caffeine
an inhibitor of phosphodiesterase, resulting in an increased concentration of cAMP and thuse production of more glucose.
Receptor tyrosine kinases (RTKs)
membrane proteins involved in signaling. Most of them become active only after binding to a hormone and forming a dimer.
RTKs act by….
phosphorylating tyrosine side chains in target proteins and this is an important step in the signaling process. This phosphorylation starts with “autophosphorylation” in which the tails of the receptor dimer phosphorylate each other.
insulin receptor substrates (IRS-1)
The phosphorylated tyrosines on the insulin receptor are binding targets for proteins known as insulin receptor substrates (IRS-1). The protein contains a common domain, called SH2 that recognizes and binds phosphorylated tyrosines. Many proteins have SH2 domains.
GLUT4
a glucose transport protein that transports glucose into cells.
The insulin signaling pathway
arising from the receptors contains a kinase cascade and results in the movement of a protein known as GLUT4 to the cell surface.
Glucose is treated by the body as….
a poison. Insulin is released to stimulate cells to uptake glucose when glucose concentration is high (as after a meal), thus reducing the blood concentration of glucose. Once inside the cell, glucose is either used or stored as glycogen.
Epinephrine/glucagon signaling
results in production of glucose and protein phosphorylation. Insulin signaling results in activation of an enzyme called phosphoprotein phosphatase that results in protein dephosphorylation.
insulin
results in reduction of glucose concentration.
insulin acts counter to the epinephrine/glucagon signaling system
Epidermal growth factor
a small polypeptide whose action stimulates cells to divide and grow. The EGF receptor that it binds to exists in cell membranes as a monomer. Binding of EGF to the monomeric receptor causes the receptor to dimerize.
