Lecture 6: Cell Signaling - Exam 5 Flashcards
(29 cards)
What is endosomal recyling?
Recycle cellular components for reuse at the plasma membrane (energy efficiency). Rab11 is apart of this endosomal recycling.
What is the most studied form of endocytosis?
Clathrin-Mediated Endocytosis
General signaling: How signals are transduced between inducer and responder. 4 ways & examples here.
1) In the head: normal induction of lens by optic vesicle. Normal. Have eye cells and eye receptors present.
2) In the head: optic vesicle cannot induce ectoderm that is not competent. We cut eye cells out and put them in a different place. Does not work, nothing happens. Tells us no eye receptor here.
3) Optic vesicle is removed; no lens is induced.
4) Tissue other than optic vesicle is implanted ; no induction occurs. No specific receptor here for this tissue.
The case of “Two heads are better than one”
In 1920, Proscholdt was intrigued by the observation that cells of the dorsal blastopore lip (DBL) are the first to show sign of differentiating in the salamander gastrula, so she set out to understand how the embryonic axes get organized. She transplanted DBL cells from one side of one embryo to the opposite side of another embryo.
The dorsal organizer
Induces ventral belly to become dorsal neural and muscle cells.
Organizes host and donor tissue into a secondary embryo with clear anterior-posterior and dorsal-ventral axis.
With the dorsal blastopore lip (DBL) transplant, what was the result?
Siamese twins. Two DBLs and two opposing heads were produced.
Which is not an aspect of morphogenetic signaling?
a. a concentration gradient of some factor
b. cell proliferation
c. changes in gene expression
These are all an aspect of morphogenetic signaling
The DBL is the only ___________ tissue in the early gastrula. It is capable of…?
self-determined ; it is capable of organizing the cells around it.
Dorsal lip cells became known as the organizer
What are the two components of every inductive interaction?
- The inducer AKA the tissue that produces the signal (or signals) that changes the cellular behavior of the other tissue. These cells are mostly secreting proteins (ligands) that influence the transcription of genes in surrounding cells.
- The responder is the cell or tissue being induced. THIS CELL MUST HAVE THE RECEPTOR FOR THE LIGAND AND THE ABILITY TO RESPOND TO THE SIGNAL = COMPETENCE
What are the scaffolding proteins in the Wnt pathway?
APC and Axin
Scaffolding means it is a structural protein that brings other things to places.
What is GSK3 in the Wnt pathway?
An active kinase.
It phosphorylates B catenin.
With no Wnt, is there transcription?
No
Wnt loss of function in frog: Wnt is required for posterior development. Discuss at least two ways that you think scientists could have caused these phenotypes.
Could add a phosphatase to dephosphorylate B-catenin.
Mutations in APC or in the complex (or in GSK3) to not have B catenin phosphorylated and then this would cause cancer because we would have overexpression.
Antibody staining tells you..?
Where and when a protein exists in a cell or EC matrix.
Describe an overview of delta notch signaling.
Very ancient: present in sponges.
A simple way to make some cells in a sheet of cells different from the others and form boundaries.
Often used to make binary decisions between cells.
Describe the mechanism of notch signaling.
Notch serves as a receptor for direct cell-cell signaling by transmembrane proteins (e.g. Delta) on neighboring cells.
The binding of Delta leads to proteolytic cleavage of Notch by y-secretase.
This releases the Notch intracellular domain, which translocates to the nucleus and interacts with the CSL transcription factor to induce gene expression.
Delta-Notch signaling. There are different ways it can work. What are two ways?
Lateral inhibition and induction.
Lateral inhibition : Two cells send similar signals, randomly one cell starts to send a stronger signal, the receiving cells adopts a different fate.
Induction: One cell induces another cell to change fate = often a binary fate decision.
However, in each case only adjacent cells will receive the signal.
Before notch signaling is activated, what acts as a transcriptional repressor?
CSL transcription factor. HDAC is bound to it CSL.
Does the cell have a skeleton?
Yes!
The components are very highly organized and reside in well defined regions of the cell.
What are the cytoskeleton functions?
-Lends architecture and support
-Provides framework for: positioning of membranous vesicles, compartments and even organelles, directing movement of materials, and cell polarity.
-Provides machinery for movement of cell
-Plays an important role in cell division
What is the cytoskeleton?
Polymer network of filamentous, proteinaceous structures
These are the components of the cytoskeleton:
-microfilaments (actin)
-microtubules (alpha and beta-tubulin)
-intermediate fibers (~70 proteins in humans: keratin, desmin, neurofilaments, lamins).
What compartment of the cytoskeleton is the smallest?
Actin (7-9nm)
(microtubules are 25 nm)
(intermediate filaments are 10nm)
What are the methods for study of the cytoskeleton?
Microscopy:
-Fluorescence
-Video
-Electron
Drugs, mutations, KO and KD in model animals/plants
What are some dynamic features of the cytoskeletal elements?
-Capable of collapse and reorganization
-Capable of stable limited “fixed” structure
-Regulated by sensing intracellular and extracellular signals
