12 Flashcards
Kinesin and Dynein role in Shh pathway in Cilium ?
In cilium-mediated Hedgehog (Shh) signaling..
kinesin transports Gli proteins and Smo toward the ciliary tip for activation,
while dynein moves Gli repressor forms back to the cell body for degradation or repression.
EVc role in Shh signalling?
EVC (Ellis-van Creveld) proteins are positive regulators of Hedgehog (Hh) signaling,
- localized at the EvC zone near the base of the primary cilium
- they facilitate Smoothened (Smo) activation and promote Gli transcription factor signaling.
what does inversin do in primary cilia?
Inversin (INVS) acts as a switch in primary cilia
regulating the balance between canonical (β-catenin) and non-canonical (planar cell polarity) Wnt signaling
- targets disheveled (DVL) for degradation = crucial for left-right axis patterning and ciliopathies.
How does inversin control Dvl levels?
Inversin (like Diego) has Ankyrin & CaM binding sites
- this controls Dvl
what does AHI1 do in Canonical Wnt signaling?
AHI1 (Jouberin) assists b-catenin entry to nucleus
- it has a SH3 domain and WD40 domains
What do WD-40 repeats/domain-containing proteins do?
WD-40 repeat-containing proteins serve as scaffolds for protein-protein interactions, regulating processes like signal transduction, transcription, and cytoskeletal organization.
i.e. B-TrCP, G-proteins, AHI1
what proteins are key to positioning basal bodies?
BBS proteins
What is the location of the Transitional Zone?
region just above basal bodies
What protein regulates cilium length?
TMEM67 (Meckelin) Transmembrane protein regulate cilia length
Negative impact of mTOR signalling at the primary cilia?
-associated with hyper-proliferation of kidney tubular cells
-formation of renal cysts – polycystic kidney disease
Flow and mTORC1 in primary cilla ?
Flow turns off mTORC1 allowing autophagy
what is a product of NPHP disease (nephronophthisis)?
Inversin
Nephronophthisis (NPHP) disrupts Ca²⁺ signaling in primary cilia - HOW?
Defective ciliary proteins (e.g., NPHP1-11 mutations) → Impair mechanosensing in primary cilia.
Abnormal polycystin signaling (PKD1/PKD2 dysfunction) → Reduced Ca²⁺ influx.
Low intracellular Ca²⁺ → Increased cAMP levels
High cAMP → Overactivation of PKA → Disrupted cell proliferation & tubule integrity.
Tubular damage and fibrosis → Progressive cyst formation and kidney failure.
Hippo (Mst1) signalling outcomes?
-kinase cascade
-control of organ size
-restrains cell proliferation when “On”
-promotes apoptosis when “On”
-keeps cells together when “On”
Hippo/Mst1 “ON “pathway (STEPS)
Mst1 (kinase) bind and phosphorylate Sav1 → Forms a scaffold for signaling.
Mst1 phosphorylates Lats1/2-Mob complex → Activates Lats kinase.
Lats phosphorylates YAP/TAZ → Preventing them from entering the nucleus.
TEAD repression → Since YAP/TAZ can’t bind TEAD, transcription of growth-promoting genes is inhibited.
what is 14-3-3 protein and what does it do?
14-3-3 proteins are a family of regulatory adapter proteins that bind phosphorylated target proteins to control signaling pathways, apoptosis, and cell cycle regulation
PDZ-containing proteins ?
PDZ-containing proteins are scaffolding proteins that recognize and bind specific motifs in target proteins,
- cell polarity, synaptic signaling, and membrane trafficking
(e.g, ZO-1, TAZ)
Hippo/Mst1 “OFF “pathway (STEPS)
No Mst1/2 activation: Mst1/2 kinases are not activated.
LATS1/2 are not activated and don’t phosphorylate YAP/TAZ.
YAP/TAZ are not kept in the cytoplasm, so they enter the nucleus.
YAP/TAZ bind to TEAD and promote transcription of growth-related genes.
Result: Increased cell growth, proliferation, and survival.
Sav1 KO results in what?
Cell proliferation
- Sav is a tumor supressor, without it Yap/TAZ are free to transcribe genes
what type of protien is B-TrCP ?
B-TrCP is an E3 ubiquitin ligase.
Function: It plays a critical role in the ubiquitin-proteasome pathway, where it helps tag proteins for degradation.
Phospho-YAP/TAZ is regulated by —- or —– if Hippo is on
14-3-3 , Ub’n
what does DAPI stain?
A-T rich regions
- nuclear localization
what localizes TAZ/YAP to the nucleus ?
- when the Hippo pathway is inactive
- the lack of phosphorylation (inhibiton of LATS1/2) localize them the the nucleus
