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what are the secretory membrane system?
golgi apparatus, endoplasmic reticulum, plasma membrane
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where does the secretory membrane system transport on?
microtubles and actin filaments
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what are the signal sequences in secretory membrane system?
FedEx system; vesicular tubular carriers
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what are the sugar systems in glycosylation?
- 2 N-acetylglucosamine
- 9 mannose
- 3 glucose
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what is the calnexin cycle?
correction pathway, sends protein out of translocon when protein is incorrectly folded
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what are the regulatory proteins that transport material from ER to Golgi?
Rab, Arf, Sar
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what is cholesterol?
leaflet in bilayer facing extracellular space
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how do we measure the movement of protein in Golgi
- transform cells with secretion protein with GFP tag (cells with a temp-sensitive mutation ER export process express FFP viral membrane protein fusion
- cells are at the restrictive temp in the start, causing accumulation of protein in ER
- when temp is lowered, trasnport can be followed
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what is the function of the Golgi?
processing and sorting functions, modifications of core sugar group originated in ER, where proteins get proteolytically processed
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where are sphingolipids made?
in Golgi (cis to trans)
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how are the sugar groups of proteins modified in Golgi?
- cis: phosphorylation of oligosaccharides on lysosomal proteins, removal of Man
- medial: removal of Man, addition of GlcNAc
- trans: addition of GaI, addition of NANA
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what are the two models that explain vesicular transport?
vesicular transport model and cis maturation model (lipids movies)
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what are the proteins made in the ER?
cholesterol and phospholipid (rafts); as cells mature, they get thicker.
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What is the role of lipid gradients along the secretory pathway?
transmembrane proteins sort to appropriate thickness of membrane; differences make PM less permeable and ER deformable for protein insertion; Golgi mix is perfect for sorting
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which lipids move forward and which lipids have retrograde
- forward flow of cholesterol, sphingolipids and phospholipids
- some selective retrograde flow of sphingolipids and phospholipids
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what is the role of coats in vesicular transport?
- formed from cytosolic proteins
- help pinch off vesicle
- select cargo for target
- coats recognize cytosolic tails of integral proteins in donor membrane
- phospholipids play role in creating domains
- motor proteins
- Arf GTPase switches
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what are the protein machinery for vesicular traffic?
- specialized coats
- tethering factors
- fusion proteins
- identities of organelles
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why are there different coat types?
control sorting and delivery routes
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what is the role of COPII?
from ER to Golgi with help of Sar1
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what is the role of COPI?
from TGN to ER Arf1
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what is the role of Clathrin?
- also Arf1; from TGN to endosomes, lysosomes
- endocytosis and from endosomes to lysosomes
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what are Arf GTPases?
- small GTP binding protein; binds to anchoring protein to form one of the coats
- associate with membranes via covalently bound myristol group to C-terminus
- regulate by GAP (hydrolyzes GTP/release from membrane/ inactivates) and GEFs (exchange GTP for GDP, recruits to membrane and activates)
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what is the function of GTP binding protein, Sar?
- COPII associated with Sar, Sar-GTP binds ER membrane
- recruits other coat subunits of COPII
- must disassemble before fusing twith target membrane to Sar-GDP
- releases other COPII subunits
- ER to Golgi
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What are the function of Sec?
- genetic secretion mutants; using coatomer to rip off vesicle from ER
- GTP to GDP releasing coatomer and releasing vessicles
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what is the role of small GTP binding Arf1?
- associated with COPI
- must be hydrolyzed before coat dissambled
- golgi to ER an din between Golgi stacks
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what are the components of membrane coats from transport of vesicle to and from ER?
cargo, cargo receptor, adaptin, clarthrin coat, coatomers (protein links cargo through transmembrane)
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how does ER proteins know to return to ER?
KDEL sequence recognized by KDEL receptor, binds to adaptin for COI trigger assesmbly of COPI, returning it back to ER
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what is the purpose of snare
transmembrane SNARE proteins in vesicles (v-SNAREs) interact specifically with target SNAREs (t-SNAREs) for forward movement of vesicles
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what is SNARE regulated by?
Rabs, GTP binding protein; coats are removed prior to fusion; interact with specific Rabs
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describe the Rab GTPase cycle
- switches that control interactions between transport carriers and docking complexes
- c-terminal geranylgeranyl
- also recruit motors
- large family about 70
- role of GDI
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what does fusion require?
- lipid bilayers are within 1.5nm of each other
- water is removed between the two membranes
- SNARE complex disassembles after fusion
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what does botox prevent?
secretion at the neuromuscular junction by destroying protein that mediates the t-SNARE/v-SNARE interactions
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what are the pathways from TGN?
- Constitutive pathway to plasma membrane (partition into lipid domains richer in cholesterol and sphingolipids
- motors on MT and actin
- endosome/lysosome pathway (large and diverse group, hydrolytic enzymes in lysosome (pH)
- secretory granule pathway
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where does AP3 coated vesicles go?
to late endosome
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where does AP1 clathrin coated vesicles go?
to endosome, lysosome
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what is the function of mannose 6 phosphate
M6P receptors put it in vesicles with AP3 trafficked to lysosome
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