Common Signalling Pathways Flashcards
What is cell signalling?
Communication between cells to govern basic cell activities and actions
What happens in signal transduction?
cells convert one kind of signal or stimuli into another
What are the 3 types of INTERCELLULAR SIGNALLING
- Autocrine signalling
- Paracrine signalling
- Endocrine signalling
List the different molecular signalling pathways
- morphogens
- notch/delta
- transcription factors
- receptor tyrosine kinases (RTKs)
What are the two proteins needed for intercellular communication?
- gap junctions (connexon)
- cell adhesion molecules (cadherin, immunoglobin super family)
The anterior, posterior and anteroposterior axes of the embryo does what?
They determine the correct locations for things like the limbs and nervous system patterning
What does excessive retinoic acid lead to
Because retinoic acid posteriorizes the body, when there’s excess, structures have a more posterior nature
A more anteriorized body structure is caused by what?
- insufficient retinoic acid
- Defects in retinal aldehyde dehydrogenase (produces retinoic acid)
Retinoic acid receptors are _________ and they __________ when activated. Their main targets are ______
- Transcription factors
- Regulate downstream gene expression
- Hox genes
Explain the metabolic production of Retionic acid
Dietary vitamin A (retinol) is oxidized by retinol dehydrogenase which creates retinal. Retinal is oxidized by retinal aldehyde dehydrogenase creating the bio active form of ATRA (All Trans Retinoic Acid) all which cellular binding proteins are controlling their concentration.
Retinoic acid can be actively degraded into inactive metabolites by an enzyme (CYP26)
What are the members of the TGF-ß superfamily and their function
- TGF-ß, BMPs, activin and nodal.
- Contribute to dorsoventral patterning, cell fate decisions and formation of specific organs
What are morphogens?
- diffusible molecules that say where a cell is generated in the body and where they go till they get to their destination
- they can be expressed in opposing gradients (dorsal ventral etc)
Name examples of morphogens
- Retinoic acid
- Transforming Growth Factor ß(TGF-ß)
- Sonic Hedgehog (patterns the ventral neural tube)
- Wnt proteins
- Bone Morphogenic Proteins (BMPs)
The Wnt-secreted glycoproteins are vertebrate orthologs of _______
- The Drosophila gene Wingless
What do Wnt proteins do?
- The control apoptosis, cell migration & cell fate specification
Explain the Wnt/ß-catenin pathway when Wnt is present
- Wnt binds to Fzd (its receptor) with coreceptor LRP5/6
- Active Fzd phosphonylates DVL which is activated
- Active DVL binds to a complex to phosphorylate GSK3
- GSK3 with phosphor is inactive and cannot phosphorylate ß-catenin
- ß-catenin goes to nucleus and activates target genes with TCF (transcription factor)
Explain the Wnt/ß-catenin pathway when Wnt is absent
- No Wnt to activate Fzd (cell surface receptor)
- No Fzd to phosphorylate DVL
- Inactive DVL cannot bind to protein complex
- GSK3 (a kinase) is active, (not phosphorylated) and it phosphorylates ß-catenin marking it for degradation
- No ß-catenin available to activate target genes