Flashcards in 7. signalling Deck (63)
what are rich in potential viral oncogenes?
signalling pathways - drivers of cancers in various settings.
what is the receptor at the top of the signalling cascade that results in cyclin D/E expression called? describe the viral version
vErbB3 lacks the extracellular part and the intracellular part is constituently active
name the central kinase that performs most of its phosphorylation at the membrane. describe the viral version
viral version has alterations meaning that it is permanently attached to the membrane meaning that it is constitutively active
name two viral oncogenic transcription factors that cannot be switched off?
v-fos and c-jun
what is conditioned medium?
this is media that has been exposed to cells and it will contain all their secretions
what is the difference between cell grown in non-cancerous conditioned medium and cells grown in cancerous conditioned medium? and what does this show?
in non-cancerous conditioned medium cells do not proliferate
in cancerous medium, cells proliferate
>cells have secreted something that triggers other cells to enter S phase.
what growth factor was being released from cancer cells?
how are cancer cells that secrete TGFβ
it can act in an autocrine manner
when an antibody that binds a RTK that recognises GF, how does this affect tumour growth?
this stops the volume of tumour increasing
how was EGF signalling first seen?
proteins harvest from salivary glands of new born mice shown to enhance development, premature opening of eyes and eruption of teeth
>after 20 years he isolated EGF
describe structure of EGF
53 amino acids
3 disulphide bridges to help maintain structure
describe the paper that first reported the discovery of EGFR
>total cells lysate of cells that respond to EGF
>purified with high affinity matrixes that bind specific glycosylated proteins
>after lots of fractioning one band was seen on gel - EGFR
what did this EGFR band have the equivalent sequence? and what gave them confidence they had found the humans receptor?
>the fact that they had identified a cellular homologue of this viral oncogene gave them confidence that they had found the human receptor
what antibody is used in an immunoprecipitation to show that when EGFR is activated by EGF it is phosphorylated?
>single TM glycoprotein of 2010 aa
what happens when EGFR is activated on the extracellular side?
activation of EGFR causes conformational changes which result in the exposure of a single stranded beta hairpin dimerization arm that promotes the dimerization to another receptor, to form a homodimer
describe the intracellular portion of EGFR
tyrosine kinas domain followed by regulatory region bearing tyrosines to phosphorylate
what happens on the intracellular side when EGFR has dimerised?
intracellular domains are close enough and in the correct orientation for trans-autophosphorylation to occur
what are phosphor-tyrosines on inside of EGFR able to do?
transduce the signal to the rest of the cascade.
what is the next protein in the pathway after EGFR? and describe its structure
it has three domains that fold independently of one another
what are the three domains of Grb2
1 Sh2 domain - this binds phospho-tyrosines
2 SH3 domains - these binds proline sich sequence and propagate signal downstream
describe the SH2 domain
it is symmetrical
two alpha helixes with some beta strands across the back
name a flexible interaction motif
what gives SH3 domains specificity and can also change its affinity to a certain peptide?
> loop structures coming off the beta barrel
> peptide sequence that SH3 is binding
what does Grb2 bind? and why?
Son of Sevenless
there are two proline rich regions in SOS
what is the EGFR receptor in Drosophila called?
what type of protein is SOS?
where is SOS located? and what implication does this have?
in the cytoplasm
>recruited to the membrane by Grb2
>Ras is a membrane bound protein
what two mutants in Drosophila look similar?
Sevenless and SOS mutants
>EGFR pathway is used in development of eyes
>each bump normally consist of 7 cells
>in mutants they only have 6 and this results in roughened appearance