Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Lecture, Wednesday, September 21, 2011
Vesicle formation & Fusion PowerPoint : Intracellular Vesicles
Different types of secretory vesicles
Vesicles that go from the ER to the Golgi are CopI secretory vesicles
Vesicles that go from the Golgi to the ER are CopII
Secretory vesicles in cytoplasm are produced from trans Golgi into cytoplasm and
formed to internalize material into cell
Slide#2
A) Exocytosis: export secretory vesicle to outside
a
...
Where does membrane come from?
ii
...
What’s the content?
iv
...
Refer to picture on top of slide#2
i
...
Refer to part B on slide #2
b
...
The membrane originates in plasma membrane
ii
...
PI = not phosphorylated
b
...
PI(3,4)P2 = Phosphorylated at 3rd and 4th carbon
d
...
or PI(3,4)P2  PI(3)P by PI(4)P phosphatase which eliminates
phosphate at position 4
f
...
Destabilizes lipid area & inner leaflets start to fuse
3) Final step of secretory vesicle, PI(4,5)P2 gets converted to PI(4)P function of
phosophatase of membrane lipid for release of vesicle membrane

Slide #17
Vesicle trafficking movement of vesicle from
Donor to target compartment
Donor to target vesicle membranes eventually fuse
1) SNARE’s
2) Rab’s: regulate docking; serve purpose of linking / anchoring Rab proteins
are GTPases
a
...
Rab GDP is a RabGTPase linked to GDP
c
...

Slide 23
How do you create holes in a membrane?
High calcium shock; pokes holes in membrane
High calcium influx when membranes pressed together creates pores for
membranes to fuse with each other
Weakens point of contact and promotes fusion during calcium influx
Slide 27
Lysosome; Key things
pH is very low
all enzymes in lysosome undergo hydrolytic reactions
hydrolases do not function properly unless the pH is low
How do you keep the pH low? V-type proton pump…pumps protons from cytosol to
lysosome; and its an ATPase to convert energy for active transport of H+ to inside
organelle against its concentration gradient; it must be functional to keep the pH
low inside the organelle for lysosome to function
Slide 29:
3 major pathways for degradation
1) phagocytosis: phagosome  lysosome
2) organelles (peroxisome, mitochondria, have a limited life, regenerated every
2 weeks) so they undergo Autophagy a process for aging, aging membrane
triggers Autophagyautophagosomebecomes lysosome
3) early endosome; endocytotic vesicle fusion; gets bigger & bigger; early
endosome accumulates proteins as it gets bigger the pH starts to lower then
gets to lysosome as pH5; late endosome has enzymes but not activated until
they reach pH 5 in lysosome; early endosomelate endosome lysosome
Slide#30
Sometimes late endosome fuses with lysosome to form endolysosome
lysosome to become final product

Slide#31
Autophagosome membranes formed around aging organelles
Digested amino acids; glucose; monomers of carbohydrates leave lysosome as
small units through different channel proteins and return to cytosol
Slide #32
Where do hydrolases of lysosome come from? Transgolgi; leaves as secretory
vesicle & goes directly to lysosome
...
2 types
i
...
Caveoli
Slide #4
1
...
Refer to drawing in class of antibody, antibody structure and epitope
3
...
The structure of an antibody is like a structure of a “Y”
5
...
Fab: binds bacteria; antibody has valency of 2 meaning 2 binding sites
but only capable of binding 1 because the binding sites are too close
together and there is physical interference
6
...
Fc: receptor on macrophage has a receptor specific to the Fc region of
the antibody and the recognition triggers……formation of pseudopods
that will surround the bacteria until it is completely enclosed
7
...
Fc binds receptor results in polymerization of actin,
2
...
that signal is the conversion of PI(4,5)P2 by PI3-Kinase to PI(3,4,5)P3
4
...
senescence: cell dies of old age
b
...
the ligand is outside bound to the receptor on the plasma membrane
Slide #10
1) Example: endothelial cells; very important layer of cells that are along blood
vessels; they internalize LDL (low density lipoprotein)
2) LDL: you have a vesicle; you have a protein that goes in and out of cell
membrane and on outside (dots are cholesterol molecules) and holds
different kind of cholesterol molecules inside
3) Inside the cholesterol is esterified meaning it has a little Fatty Acid tail
4) The cholesterol in the membrane is unesterified
5) LDL = Low Density Lipoprotein
6) 500 phospholipid molecules;
a
...
inside of that is 1500 esterified cholesterols
slide #11
what happens when you have Endocytosis?
1) Part A: Endothelial cell has receptor for LDL protein
a
...
Formation with a lot of LDL
2) Part B: Disease defective receptors cause people to have low cholesterol
a
...
So low cholesterol disease causes leaky membranes which means
these people have a higher risk of cancer
c
...
Dr
...

Slide#5
The signal that trigger the polymerization is the PI-3 Kinase
...
2% of membrane is internalized
b
...
Where do they go?
i
...
Lining of endothelial cell; blood vessel
b
...
Formed at lipid rafts
d
...
By internalization with caveolin the proteins are not destroyed by the
low pH of endosome so activity of protein is maintained
f
...
Internalization (refer to drawing in class of apical, basal, basal
lateral & tight junction with caveosome)

ii
...
Transcytosis: All caveosomes undergo transcytosis whereas
some Clatherin coated vesicles undergo transcytosis
g
...
an example is LDL: (understand how LDL triggers Endocytosis prev
...
Key: hydrolytic enzymes (in lysosome) really degrade
integrity of LDL destroying the proteins & the most
important outcome is the
i
...
Conversion of esterified cholesterol to
unesterified cholesterol
8) Then Cholesterol free to leave lysosome for whatever use that
is required
9) All free cholesterol is unesterified when it comes out of
lysosome
10)Channel proteins in lysosome allow amino acids and
monomeric carbohydrates to go through
11)The cell can sense cholesterol concentration and over
abundance of cholesterol stops in situ biosynthesis of
cholesterol ( triggers the body’s production of cholesterol to
stop)
Slide #14
body’s location of the endosome…usually close to the plasma membrane so when
the secretory vesicle is internalized they don’t have far to go because they fuse with
endosome at 1st stage

The late endosome and lysosome are located near the nucleus & Golgi (further away
from plasma membrane)
Refer to drawing in class of cell with apical and basal side…
...

Ubiquitin binds, invagination of endosome membrane occurs, this forms vesicles,
the vesicle internalizes some cytosolic fluid; ubiquitin, and the receptor bound to
the cargo this complex becomes a vesicle within the endosome and is called multi
vesicular bodies…
...
The lysosome chews up the receptor, ligand,
and ubiquitin…
...


Slide #21
Clatherin coated intestinal cells on epithelial side
The cell has an Fc receptor on basal side that attaches itself to the FC region on
Antibody on mom’s antibody and that triggers regulated Endocytosis where
secretory vesicles are formed, decoated, and then fused with endosome, then
endosome(one pathway) can be budded again to form another endosome and
budding process moves closer to other end of cell and eventually there is a secretory
vesicle budded from this endosome, closer to this membrane producing a secretory
vesicle that will eventually fuse with the basal membrane releasing the antibody to
the other side; this is an example of transcytosis, the transfer is intact, the antibody
makes it’s way to baby’s bloodstream…
...
All caveoli are transcytosed
Slide #34
What happens with a synapse? (another example of exocytosis)
1)Constitutive secretory pathway meaning vesicles are continuously formed
Transgolgi form secretory vesicles that migrate to the plasma membrane via
cytoskeleton which has a network of micromotor proteins where it moves vesicles
to the plasma membrane where it will fuse and release soluble protein out of cell
this process is continuously happening
...
The signal is a hormone and the signal moves via signal
transduction pathway which causes the secretory vesicle to move along
cytoskeleton vial the help of motor proteins until the secretory vesicle fuses with
the plasma membrane and exports the hormones out of cell, they will not move to
the plasma membrane and fuse unless there is an external signal (hormone)…
...

Slide 47: Exocytosis of Synaptic vesicle this example is only in neural cells that
produce neurotransmitters in neural vesicles

Case study for exocytosis and Endocytosis and how it recruits neurotransmitter and
packages it for release to the synapse
Synaptic vesicles release neurotransmitter from one side to another by secretory
vesicle and neurotransmitter that can be recycled back to the axonal terminal;
unique packaging only neural cells that produce neurotransmitter; neural cell and
Transgolgi produce a synaptic vesicle; not much is exocytosed outside; you have
exocytosis followed by Endocytosis; vesicle returns to cell with a neurotransmitter
and it is concentrated through this type of translocation, then eventually exocytosed
again
So in summary…secretory vesicle without neurotransmitter produced 1st; vesicle
has to be returned to cell empty where it is packed with neurotransmitter by you or
the same type of vesicle can be produced by the endosome where it is also devoid of
neurotransmitter; packaging of secretory vesicle with neurotransmitter (i
...

Achetylcholine, beta-gamma buteric acid, adreniline)



---