8.2 Flashcards
Signal Transduction Pathways - II
Some receptors are activated by extremely low concentrations of ligands:
(10-9 – 10-11 M).
ligands can also be called:
Growth factors (EGF): but also include hormones (e.g. insulin)
Is the response time of ligands fast or slow?
The response time is usually slow (hours) since they alter gene expression
The response of ligands / EGF involves :
Phosphorylation of a downstream target or of the receptor
some receptors are activated by extremely low concentrations of ligands: many such receptors are:
Tyrosine kinases
RTKs usually have a ___ membrane spanning domain in contrast to G- protein-coupled receptors which have __.
RTKs usually have a single membrane spanning domain in contrast to G- protein-coupled receptors which have 7.
RTKS: ligand binding often induces:
aggregation of the receptors, followed by autophosphorylation (one receptor phosphorylates tyrosine residues of a neighboring receptor).
Ras:
Small GTP binding protein. When bound to GDP it is inactive, when bound to GTP it is active
GRB2:
An SH2 domain-containing protein (binds to phosphotyrosine residues). Mediates attachment of Sos to the activated EGF receptor
SOS:
Nucleotide exchange factor for Ras, activates the GTPase.
Many targets of MAP kinase are:
Transcription factors
Many targets of MAP kinase are:
Transcription factors
Many targets of MAP kinase are transcription factors. The Ras-Raf MAP kinase pathway can activate
~160 genes
Any targets of MAP kinase are transcription factors. The Ras- Raf MAP kinase pathway can activate ~160 genes called
Early response genes
Many targets of MAP kinase are transcription factors.The Ras- Raf MAP kinase pathway can activate ~160 genes called early response genes (needed for the cell to enter and progress through the cell cycle). The result of this signaling pathway is called:
Cell proliferation, differentiation and survival.
The Ras-Raf MAP Kinase pathway:
