Slow Response Pathways Flashcards
Why are some cellular responses to signals slow, while others are fast?
The slow responses involve gene expression
What are 4 common components of slow response pathways?
- Formation of a ligand/receptor complex
- Kinase activation
- Activation and/or translocation of a transcription factor
- Nuclear phosphatases to shut off the transcription factors
What type of receptors do long term pathways use?
Tyrosine kinase receptors
What are the similarities and differences between RTKs and cytokine receptors?
They both cross the membrane once and have an extracellular ligand binding domain. RTKs are Y kinases themselves, while cytokines receptors are only associated with Y kinases
What is typically a signalling molecule for an RTK receptor?
A growth factor
What are the typical cell responses for a long term pathway?
Cell growth, proliferation, survival, differentiation
What happens to RTKs when the ligand binds?
They dimerize with another nearby receptor and cross phosphorylate each other in the Y rich areas
Why do RTKs cross-phosphorylate each other?
Phosphorylated tyrosines are really attractive to proteins with SH2, SH3, or PTB domains, so they get recruited to the membrane
Is every RTK activated exactly the same?
No, some form homodimers, some are heterodimers, some are already dimerized, some require multiple ligands to bind
Why does an RTK need to recruit other proteins to activate a signalling pathway?
Its stuck in the membrane, so other things need to come to it for the receptor to phosphorylate them and activate them
What is a kinase cascade?
Sequential activation of kinases, where each one phosphorylates and activates the next one
How does activation of a MAPK pathway result in cell division?
Results in the expression of hundreds of early response genes that the cell needs before it enters S phase. A lot of these are transcription factors that will activate genes needed a little later
How similar are the Ras/MAPK pathways, the p38 pathways, and the JNK pathways?
Quite similar in terms of structure and sequence, but different enough that chemicals inhibit only 1
