L.6 Vesicle Trafficking, Expcytosis, Ednocytosis

Proteins made in ER targeted to ____ or _____ side via ____

• apical

• Baselateral*

• Golgi

Proteins/molecules made in RER are transported by ____, to _____

• Small membrane vessel

• Cis side of golgi

Type of vesicle ER→Golgi

Transport

Type of vesicle Golgi→plasma membrane

Secretory

Transport of vesicles in ER and Golgi flow in ____, to create a _____

• both directions

• Cycle

Describe motion of ER/Golgi vesicles

• flow from ER to Golgi to final destination with cargo molecules

• from Golgi → ER to return molecules

___are specific to vesticle direction and flow

Protein coating

Which protein on vesicles ER→ cis Golgi

COP II

Which protein on vesicles Cis Golgi→ER

COP I

Which proteins in vesicles trans Golgi→lysosome/membrane

Clathrin

Coats of protein around vessicles function

Coats help target to endpoints

Clathrin composition (components)

3 heavy chain proteins and 3 light chains

Clathrin structure

Polyhedron (lattice that coats vesicle)

Clathrins used for what processes?

• Protein transport

• Endocytosis

Intracellular vessicles can be transported long distances via

Microtubule networks

Example of cell where paehged* vesicle travels long distance

Neuron

How do vesicles move?

• microtubule network allows path

• Protein coat on vesicle use energy to pull along tubules

Vesicles flow in the following dorection(s) (relative to molecules)

• away from nucleus (anterograde)

• Towards nucleus (retrograde)

Vesticles connect microtubule network via

Protein complex

Membrane vesicles contain cargo such as _____ are linked via _____ to microtubule network and the _____ that crawls on the net work (____)

• neuro transmitters

• Protein

• Motor

• Dynein*

Function of dynein

Use energy to move along microtubules and pull vessicles with it

Endocytosis is?

Plasma membrane engulfs outside material; brings inside

Expcytosis is?

Vesicles made inside fuse with membrane and release contents outside

3 types of Endocytosis

1. Phagocytosis (solid particle)

2. Pinocytosis (fluid)

3. Receptor mediated (based on receptors)

Phagocytosis process

• engulf (bactierum) with plasma membrane, form phagosome

• Phagosome merges with lysosome

• Enzymes digest bacterium

Cholesterol in blood found as _____, which binds to _____

• low density lipoprotein (LDL)

• Receptor on liver cell

Receptor mediated Endocytosis (cholesterol) steps

• LDL bonds to receptor on liver

• Puts surrounded LDL, bring inside

• Vesicle loses Clathrin coat, LDL dissociates from receptor

• Receptor recycled to surface

• LDL degraded in lysosome

Cholesterol receptor characteristics

In put, coated with clatherin

What is LDL cholesterol degraded to?

• cholesterol

• AAs

• FAs

Clatherin mediated Endocytosis is used to ____

Recycle and regulated number of other receptors on cell surface

Exocytosis requires what to occur?

Membrane of vesicle to fuse with plasma membrane

Fusion (of membranes) controlled by steps (2)

1. Complementary proteins in vesicle/ target surface of membrane

2. Ca2+, via Ca2+ sensitive protein on vesicles

Ca2+ content of fusion allows for what??

Controlled, quick release of substances

Which is always ready for vesicle fusion?

Membrane

Vesicles fusion steps

• complementary proteins able to line up fus with target by anchoring

• Ca2+ added, release protein

• Trigger vesicle fusion

• Release cargo

Nobel winners regarding this unit

1. Genes control transport of vesicles to different places, mechanisms for moving proteins

2. Proteins coat vesicles and cell membranes, allows to anchor together

3. Ca2+ triggers vesicles fusion

Release of neurotransmitters

• nerve impulse down axon

• At synapse → inside Ca2+ concentration goes up

• Release NT across cleft

• Target is dendrite of neighbour

Exocytosis- what happens with fused membranes?

• membrane proteins endocytosed (clatherin dependant) into endosome

• Vesticles recycled, refilled, cycle restarts

Steps of synaptic membrane recycling

1. Release NT

2. Synaptic vessel membrane absorbed with clatherin pits Endocytosis

3. Endocytosis vesselfus with early endosome

4. New vesicle pinched from endosome and refilled

Release of histamine process

• bind to allergen (to mast cell)

• Trigger Ca2+ release

• Exocytosis of histamine

• Histamine binds to receptors

• Allergic response

Histamine has receptors on what?

• immune system cells

• Smooth muscle cells

• Endothelial cells

What is collagen

• from fibroblasts

• Part of ECM

Collagen production released during?

Scarring

Synthesis of collagen

• made/ processed in ER

• assembled into fibrils in Golgi

• Transport to membrane (final maturation)

• Vesicles fuse at membrane and release

• Fibrils align (form tendon)

High cholesterol rush* for _____

What can cause high levels regardless of of diet?

• cardiovascular disease

• Genetic defects can cause Familial hypercholesterolemia (FH)

Person with high cholesterol, cells make ___+_____, binding receptor to cholesterol. This binding does what? What is the result?

• receptor (LDLR)

• Protein

• Targets receptor to be degraded and not recycled

• Higher cholesterol levels

How does antibody deregulation* lower cholesterol?

• antibody binds to proteins so unable to bind to LDLR receptors

• When LDLR endocytosed, recycled, not degraded

• More receptors on surface proportional to perpendicular* cholesterol

Proteins in vesicle and membrane ____ so it is ready for _____ and will _____

• target vesticle and hold ready (anchor)

• Higher Ca2+

• Release contents