Topic 8 Flashcards
what are the general componts of a cell signaling pathway?
1) First messenger
2) receptor protein
3) upstream signaling proteins
4) second messengers
5)down stream signaling proteins
6) target proteins
Endocrine vs paracrine vs autocrine
endocrine hormones are produced by secretory glands which pump the hormone into the blood for long distance transport which interact with receptors on tissues
Paracrine small peptides which traval short distances to receptors on nearby cells
Autocrine are also small peptides which travel short distances to activate receptors on the same cell
how does signal amplification by second messengers work
second messengers cause a chain reaction of activation threw activation of down stream enzymes for example A generates second messenger molecules which activate enzyme B and for each activated enzyme B 100 enzyme Cs are activated.
4 classes of Eukaryotic receptors proteins
1) G protein- coupled receptors
2) receptor tyrosine (adaptor proteins)
3) TNF (adaptor proteins death domain)
4)steroids (straight to receptor)
what are G protein coupled receptors involved in
Vision
Taste
Smell
Heterotrimeric G proteins are composed of what
Alpha beta and gamma subunits which aids in signaling in the cAMP and PI pathway
How many Transmembrane helices do G protein coupled receptors have and how are they oriented in the PM
they have 7 and they are oriented with the N terminus on the outside of the cell with the C terminus on the inside
Activation of Heteromeric G protein activation
1) receptor activation, which results in a conformational change in the receptor conformation allowing for GPCR binds the complex
2)The binding to the complex promotes exchange of GDP to GTP
3) this GDP to GTP exchange results in disassociation of the GPCR subunits
4) the disassociation of GPCR results in the regulation of down stream subunits
Shared vs Parallel pathways
A parallel pathway is when two pathways begin at the same time which work to gain the same product
A shared pathway is when to pathways work together to make a final product
Activation of Protein Kinase A by cAMP
1) 4 cAMP molecules bind to the R2C2 complex causing it to disassociate into 2R units and 2PKA units
2) the 2 PKA units are active monomers
how is GPCR signaling terminated
through the recycling of the receptors via endocytic vesicles after ligand binding
Once the GPCR is no longer needed BARK phosphorylates the complex allow B subunits to bind placing GPCR in a endocytic vesicle
Receptor Tyrosine Kinase (RTKs)
seconds majour class of signaling protein which have one transmembrane helix
Growth Factors and RTKs
growth factors Bind to RTK’s which result in cell division
mutations in the Ras proteins can result in cancer due to uncontrolled cell division
what is the structure of insinel and how many moeulces are needed for the pathway to activate
The receptor is a dimer and only one molecule is needed for activation
what does PI-3K signalling lead to in the insulin pathway
Increase in glucose uptake and glycogen synthesis, reducing blood glucsose
