12.1 Signal Transduction IV Flashcards
What are the 4 well studied signaling pathways that involve degradation or regulated proteolysis?
- Notch/Delta
- Wnt/beta-catenin
- Hedgehog
- NFk-B
Delta signaling is an example of a ______ signaling event.
Contact-dependent where a cell tells its neighbors what to do.
Notch is a _____, whereas Delta is a ________.
Receptor
Ligand
How does the Notch/Delta pathway apply in nerve cell development of drosophila?
When an epithelium cell begins to develop as a neural cell, it inhibits neighbor cells. Nerve cells express Delta signal on the surface that binds Notch receptors on adjacent cells and prevents them from also becoming a neuron. In this way, the correct proportion of neural and epithelial cells are maintained.
Notch receptor gets modified in ____ places but ____ are dependent on delta signaling.
3
2
The cleaved tail fragment of Notch enters the _____ where it activates a ________.
Nucleus
Transcription factor and regulates gene expression.
T/F
Notch is recycled after proteolysis.
F
Unlike most receptors, Notch cannot be recycled. Once it is activate by proteolysis, it cannot be rejoined to inactive form.
What happens without the Wnt signal?
B-catenin is phosphorylated by a degradation complex and it is then targeted for proteolytic degradation by protein degradation and recycling in cells. This means there is no transcription of Wnt target genes
What happens when Wnt signals are present?
Stabilizes the transcription enhancer B-catenin. B-catenin accumulates and migrates to the nucleus where it then displaces Groucho. Transcription of Wnt target genes occurs.
Wnt signaling is involved in a large number of ___________ events. Give one example.
Developmental events.
Regulating the orientation and distribution of epithelial hair forming cells in drosophila.
Mutations in what pathway alter the hair pattern in drosophila?
Wnt signaling pathway. Mutations cause randomly oriented bristles leading to the appearance of being frizzled or disheveled
What happens without the hedgehog signal?
Ci protein (cubitus interruptus) is targeted for degradation. Functions as a repressor: However, it is only a partial degradation and results in a small negative regulator of gene expression being produced. The negative regulator enters the nucleus and inhibits the production of hedgehog regulated genes.
What are the 3 transmembrane proteins associated with the Hedgehog signaling pathway?
iHog
Patched
Smoothened
What does NFkB do?
Latent regulator of gene expression…..it is always around in the cell waiting for activation. Enhances antibody production by B cells.
What happens with NFkB in the absence of an activating signal?
NFkB is bound to an inhibitor called IkB (inhibitor of NFkB)
What are the receptors in the Wnt/B-catenin pathway?
LRP and Frizzled
What are the receptors in the Hedgehog signaling pathway?
iHog and patched
What is the signaling ligand in the Hedgehog pathway?
Hedge
Smoothened is present on _________ membrane.
Intracellular vesicle membranes rather than the plasma membrane.
Binding of hedgehog ________ repressor activity of patched.
Deactivates
What signaling pathway is used by inflammation and stress signals and receptors?
NFk-B signaling system
