Bio Lecture 10 - Vesicular Transport

secretory, secreted, lumen

The endoplasmic reticulum is the site of synthesis of proteins of the '____________' pathway. This includes membrane proteins that will eventually either remain in the ER or be targeted to the Golgi, or endosomes, or lysosomes or the plasma membrane. It also includes proteins that are _____________ out of the cell, or reside in the ___________ of the ER, or Golgi, or endosomes or lysosomes.

endoplasmic reticulum

The _____________ ________________ is the entry point for proteins destined for a variety of locations.

sequential, budding, fusion, topologically equivalent

Transport between ____________ membrane bound compartments involved the formation of a transport vesicle by __________, following by __________ with the correct target membrane. During this process, both the membrane topology of the lipid bilayer is preserved, as is the topology of membrane proteins. Therefore, the lumen of the ER, Golgi and endosomes are __________________ _______________ to outside the cell.

coated, coats

____________ vesicles transport cargo from the donor to target organelles. Vesicle ________ differ depending on the transport step they are mediating.

clathrin, selection, adaptins, clathrin, adaptins, dynamin, shedding

Formation of __________-coated vesicles involves (1) the ___________ of cargo to be transported by transport receptors, (2) binding of __________ to the cytosolic tails the cargo receptor proteins, (3) binding of ___________ to ___________ to start formation of a vesicle, (4) pinching off of the vesicle by ___________, and (5) subsequent ___________ of the membrane coat.

recognition markers

Transport vesicles need to have ____________ _________ on them so that they fuse with the correct target membrane.

shape

Coating proteins help to ______ the membranes into vesicles.

clathrin, COPI, COPII

The three types of coats we mention are ____________, ________ ___, and ________ ___.

GTP, sheds

Dynamin uses _____ to pinch of vesicles. After doing so, the free vesicle ________ its adaptin and clathrin.

Rabs, SNAREs

Two major types of recognition markers are involved, ______ and _________.

dynein

ER to Golgi transport vesicles move toward the minus ends of microtubules as they contain __________.

kinesin

Golgi to plasma membrane vesicles move toward plus ends of microtubules as they contain _________.

tethering, hydrolyzed, specific

The active Rab binds to ___________ factors on the target membrane, which docks the vesicle there. During this process, the GTP is ____________, and the Rab protein is recycled for another round of bringing in vesicles. There are many Rab proteins; each one is __________ for a vesicular transport step.

Rabs

______ are small GTP-binding proteins ('molecular switches') that in their active GTP-bound state are associated with the transport vesicle.

v-SNARE, t-SNARE, specific

Transport vesicles also carry a transmembrane protein called a ___-________. This protein binds to a membrane protein on the target membrane called a ___-__________. There are many of these proteins, each __________ for each transport step.

Rab, tethering, SNARES

_____ proteins, _____________ proteins, and ___________ direct transport vesicles.

1.5

The two bilayers must come within ____ nm of each other to allow membrane fusion in SNARES.

unfavorable

Water must be displaced from hydrophilic head groups in membrane fusion, despite the fact that it is energetically ______________.

ATP

After membrane fusion, SNARES are pried apart in a reaction that requires ____.

synthesis, golgi, delivery

The secretory pathway involves _________ of proteins in the ER, their transport and processing in the _______ apparatus, and then sorting and __________ to their final destination.

oligosaccharide, asparagine, N linked glycosylation, cytosol

During synthesis of proteins on the ER, a large __________________ is transferred from a lipid-oligosaccharide donor to particular _____________ side chains. This is called ___-___________ ________________. These protein-linked oligosaccharides never reside in the ___________.

cis golgi network, stacked, cisternae, cis, medial, trans, trans golgi network

Vesicles leaving the ER are targeted to the Golgi apparatus. The first stop is the _____. The next stop consists of a set of __________ membranes (like pita breads) called ____________, each with distinct functions and through which secretory proteins are transported . The compartments are called ___-, _________- and _____-Golgi, and the final compartment after these three cisternae is the _____-________ ___________(TGN).

modified, TGN (trans golgi network)

The Golgi has two functions. First, the oligosaccharide side chains are sequentially _____________ as the proteins pass through the Golgi. Second, at the _____ they are sorted and transported in vesicles to their next compartment - such as the endosome on the way to the lysosome, or the plasma membrane.

cisternal maturation, vesicle transport

Two models for protein movement through the Golgi were presented. Most traffic appears to move according to the ____________ ____________ model, but there is evidence for some movement according to the _________ ____________ model as well.

constitutive, regulated

There are two vesicular routes from the TGN that result in exocytosis at the plasma membrane. The '______________' pathway delivers vesicles to the plasma membrane and is not regulated. Cargo whose release needs to be regulated - for example release of insulin following a hormonal signal - is first packaged into storage secretory vesicles and then released from the cell when the appropriate hormonal signal is received. This is called '____________' secretion.

hydrolytic

Lysosomes contain many different ____________ enzymes to break down all macromolecules, including proteins, carbohydrates, nucleic acids and lipids.

Lysosomal

___________________ sorting requires a particular oligosaccharide modification.

Plasma Membrane

___________ ________________ sorting does not require a signal; it is the default pathway.

N linked glycosylation, modified

Lysosomal enzymes are synthesized and subject to ___-_________ _______________ in the ER, transported to the Golgi apparatus where their oligosaccharides chains are __________ to identify them as enzymes destined for the lysosome.

endocytic

The ____________ pathway involves taking up material from outside the cell. This cargo is first delivered to the early endosome.

Low density lipoprotein, receptor-mediated endocytic, receptor, vesicle, endosome, acidic, dissociate, surface, lysosome,

Work on the uptake of LDL (____ _____________ ________________, a particle containing protein, phospholipids and derivatized cholesterol and a major carrier of blood cholesterol) first established the _________-____________ ______________ (RME) pathway. This RME pathway involves: (a) binding of LDL to the surface LDL ____________; (b) internalization of the receptor-LDL complex from a coated pit into a coated ___________; (c) delivery of the receptor-LDL complex to the early ______________; (d) under the mildly _________ conditions of the early endosome, the LDL and LDL receptor ____________; (e) return of the LDL receptor to the cell ___________; (f) movement of the free LDL from the early endosome to the late endosome, and then to the ____________; (g) in the lysosome, the protein parts of LDL are degraded and the cholesterol released for use in membrane biosynthesis.

bind, take it up

Mutations in the LDL receptor cause hypercholesterolemia by receptors that cannot ________ to LDL. Or, receptors that can, but they cannot ______ __ __.

Hypercholesterolemia

Too much LDL in the bloodstream causes a disease known as

CopII

Coating that takes vesicles from ER to Golgi.

CopI

Coating that takes vesicles from Golgi to ER.

Clathrin

Coating that takes vesicles from Golgi to peroxisome/lysosome

light, heavy, fidget spinner, cage

Clathrin is made of three _______ chains (inner) and three _______ chains (outer). It looks like a __________ __________. These molecules adhere to one another in a way that makes a circular _________, and thus a vesicle.

cisternal maturation, vesicular tubular cluster, vesicle transport, cisterna

The ____________ __________ model has a ___________ __________ ________ that migrates itself as a cisterna through the golgi. The ___________ ____________ model simply has the CGN, the cisternae, and the TGN in which vesicles bud from one ____________ to the next.

GTPase

Rab is a ________.

rab, markers

Each organelle and each type of transport vesicle carries a unique combination of ____ proteins, which serve as molecular __________ for each membrane type.

asparagines, ER

Many proteins are glycosylated on ______________ in the ___.

dolichol, oligosaccharyl transferase, serine, threonine

Each oligosaccharide chain is transferred as an intact unit to the asparagine from a lipid called __________, catalyzed by the enzyme ______________ ______________. Asparagines that are glycosylated are always present in the tripeptide sequences asparagine-X-_________ or asparagine-X-_____________, where X can be almost any amino acid.

ER, golgi

The ___ is what attaches the oligosaccharide to asparagine residues while the ______ modifies it accordingly.

glucose, mannose, N acetylglucosamine

Oligosaccharides attached to asparagine residues can be made of _____________, ______________, and ___-_______________________