Cell Biology - Vesicular Transport

Endomembrane system

Vesicular transport is a mechanism for trafficking of macromolecules (especially protiens) in the _____ ______ of a cell

Donor or target

All endomembrane organelles and the plasma membrane are potential _____ or _______ compartments for vesicular transport

anterograde transport

Movement through endomembrane components

ER -> Golgi (cis,medial,trans) -> destination

Describe the flow of anterograde movement

Retrograde transport

Reverse movement of vesicles from the Golgi back to the ER

Vacuole, early endosome, constitutive secretory vesicle, and specialized secretory granule

Final destinations of anterograde transport

constitutive secretory vesicle and specialized secretory granule

What two post-Golgi destinations can lead to exocytosis (constitutive or regulated)

Constitutive secretory vesicle

Which post-Golgi pathway is unable to use retrograde transport

Specialized secretory granule

Which post-Golgi destination requires a + stimulus/ signal for exocytosis to occur

signal

Constitutive exocytosis does not require a ______ while regulated does require a signal (Constitutive secretory vesicle v specialized secretory granule (+ signal))

Newly synthesized endolysosomal or vacuolar proteins and newly synthesized units of bilayer lipids

What kind of materials are transported from the ER to the Golgi to Endosome/ Lysosome/ Vacuoles during anterograde transport

Endocytosis -> early endosome > recycling endosome -> exocytosis

The recycling pathway follows what order

Early endosome

Main sorting station for many materials entering the cell; determines whether materials should be recycled or sent for degredation

Late endosome/ MVB ; Recycling endosome

If a early endosome determines the materials need to be degraded it is transferred to the _________ while if it needs to be recycled it is sent to the _____

Physical formation of vesicle and cargo enrichment at the donor compartment; Vesicle fission from the donor compartment; directional motor protein drives the movement of the vesicle along microtubules; vesicle docking and fusion with the correct target. compartment; Cargo unloading into the target compartment and generation of retrograde vesicle as needed

What are the basic steps for transport within the endomembrane system

Coat proteins, membrane shaping and fission proteins, and cargo receptors

The process of the physical formation of vesicles and cargo enrichment and vesicle fission from the donor compartment primarily involves what molecular machinery

Vesicle Rabs and associated Rab effectors and the network of microtubule tracks

The directional motor protein-driven movement of vesicles along microtubules involves what molecular machinery

Rabs and associated Rab effectors on both vesicle and target compartments (especially SNAREs)

Vesicle docking and fusion with the correct target component involves what molecular machinery

Vesicle coats

_____ ______ physically interact with specific cargo receptors to aid in loading of soluble cargo as well with TM cargo proteins

Membrane-shaping and fission-triggering

Coat proteins recruit ______ and ______ proteins

Donor membrane

Coat proteins dissociated off the vesicle once freed from the ____ _____

Cytosolic

Different endomembrane compartments will feature different coated domains on the ____ side of their membranes

Coat proteins

____ ____ associated onto the cytosolic membrane surface and trigger recruitment of the molecular machinery needed for vesicle formation and appropriate cargo enrichment

cargo receptors

The _______ ______ binds to soluble cargo within the lumen or EC space

Rabs

Small G proteins with a dynaomic lipid anchor; acts as a molecular switch involved in coordinating vesiclar transport

GDP-bound ; GDI

In a Rabs inactive (_____ _____) bound state, the lipid anchor is conformationally hidden within the interior of the Rab structure or bound up by a seperate regylatory protein (____)

GDP

Inactive Rab is bound to

GTP

Active Rab is bound to

GDI

Protein which keeps Rab inactive

Rab-GEF

Protein which facilitates the exchange of GDP -> GTP for Rab to active the protein

Organelle or vesicular

Once active, Rab is able to use its lipid anchor to attach to the cytosolic surface of an _____ or ______ membrane

Rab effectors

Proteins recruited by activated Rab which facilitate functions for vesicular transport such as vesicle movement, tethering, and membrane fusion

Rab-GAP

Once Rab has performed its function, it returns to its inactive state (GTP -> GDP) by which protein

Rab domain

Anchored Rabs recruit Rab effector protiens to form a ______ _____ on the membrane

Tethering proteins

Important category of Rab effectors; mediates an initial relatively non-specific interaction between vesicle and organelle (or organelle and organelle)

SNAREs

Long TM proteins which interact in highly specific ways to trigger membrane fusion

SNAREs

A vesicle/ organelle or organelle/organelle can only match together if a correct mollecular match is first made between the _______ on each membrane

match

The inital tethering helps bring the SNAREs into close proximity but fusion only proceeds if the SNAREs _____

Vesicle coat proteins

Clatherin and COP I/II are what kind of proteins (within the donor compartment)

Adaptor protein

Protein which helps connect cargo proteins to the vesicle-coat machinery during vesicular transport; selects cargo and helps package it into transport vesicles

Membrane-shaping

Coat and adaptor proteins also recruit ______ to the cytosolic face

Membrane shaping proteins

Proteins that help bend and curve cellular membranes to facilitate the formation of transport vesicles during budding

Membrane fission protein

Dynamin is what kind of protein

Dynamin

GTPase protein responsible for pinching off budding vesicles from cellular membranes during fission

v-SNARE and t-SNARE

In order to facilitate vesicle fusion to a target membrane during a vesicular transport, a ________ must bind to a matching ______

t-SNARE

Target membrane SNARE

v-SNARE

Vesicle membrane SNARE

Kinesin

Motor protein that uses energy from ATP hydrolysis to transport vesicles, organelles, and other cellular cargo along microtubules (anterograde)

+

Kinesin moves in what gradient along a microtubule

Centrosome; cell periphery

Kinesin generally moves away from the _____ and towards the ___ ____

Dynein

Motor protein powered by ATP hydrolysis that transports vesicles, organelles, and other cellular cargo along microtubules (retrograde)

Guanine NT; Rab-GTP

A vesicle-specific Rab will be activated by ________ _____ exchange (triggered by Rab-GEF), to expose a lipid anchor that allows ________ to dock onto the cytosolic face of the vesicle

Rab effectors

Once Rab-GTP has docked onto the membrane, it will recruit and stabilize additional ___ _____ into a Rab domain

Retrograde or retrieval vesicle

Cargo receptors, and any escapees will be packaged into ____ or _____ ____ for return to the origal donor compartment following fusion of the vesicle into target location

After fusion, vesicle Rab will be inactivated by GTP hydrolsyis by ______ _____ and dissociated into the free cytolic Rab-GDP pool