Intracellular Vesicular Traffic Flashcards
What type of coated vesicles are involved in endocytosis?
Clathrin coated vesicles
Endocytosis
the taking in of matter by a living cell by invagination of its membrane to form a vacuole
What type of coated vesicle are involved in the movement of vesicles off and onto the trans Golgi?
Clathrin coated vesicles
What type of vesicles mediate movement of Vesicles between the ER and Golgi as well as between Membrane stack within the Golgi?
Non-Clathrin coated vesicles
Coatomer
complex of proteins
COPI
retrograde movement from the medial -> cisternae -> ER
COPII
mediates movement from the ER -> Golgi
Cisternae
flattened membrane disk that makes up the endoplasmic reticulum and Golgi apparatus
What structure does a Clathrin molecule have?
Triskelion
What are the steps to vesicle formation using Clathrin?
Coat assembly and cargo selection, bud formation, vesicle formation, uncoating
What is used to uncoat the clathrin from vesicles?
Chaperones that act as uncoating ATPases
Dynamin
GTPase which helps pinch off vesicles from the membrane
How does Dynamin pinch off vesicles?
Dynamin polymerizes around the neck of the pit and then, binds and hydrolyzes GTP to pinch off a vesicle
What control the coat assembly?
Monomeric GTPases
ARF
GTPases for COPI and Clathrin
Sar1
GTPases for COPII
What is the Result of GTP hydrolysis of the coating of vesicles?
Coat Disassembly
syntaxin (t-SNARE)
Attached to nerve cell plasma membrane
synaptobrevin (v-SNARE)
attached to vesicle
Snap25 (t-SNARE)
SNARE protein
What does NSF do?
Dissociates SNARE proteins after the vesicle has fused to the membrane
Rab protein GTPases
direct vesicles to the right compartment
How many known Rab proteins are there?
30
BiP and clanexin
Chaperone proteins that ensure proper protein folding
How is Transport from the ER to the Golgi mediated?
Vesicular Tubular clusters
How are Vesicular Tubular clusters formed?
NSF dissociates the t-snare/v-snare complex on free vesicles, v-snare from one vesicle binds with the t-snare of another causing the vesicles to attach to one another, vesicles become one through homotypic membrane fusion
How do vesicles move from the ER to the cis Golgi network?
COPII coated vesicles leave the ER and form vesicular tubular clusters, these clusters are moved along microtubules by motor proteins to the cis Golgi network
KDEL
a target peptide sequence in the amino acid structure of a protein which prevents the protein from being secreted from the endoplasmic reticulum (ER)
What happens to proteins with KDEL that end up in the cis-Golgi network?
They are returned to the ER
What may be considered a main regulator of binding?
changes in pH
What are the three section of the Golgi Apparatus?
cis Golgi network, Golgi stack, and the trans Golgi network
What is the Aggregation of proteins with the same function called?
Kin recognition
What is a main difference between proteins from the plasma membrane versus proteins from the ER and Golgi?
ER and Golgi have shorter transmembrane segments
How determination for protein sorting made?
length of transmembrane regions
cis Golgi Network
Sorting - phosphorylation of oligosaccharides on lysosomal proteins
cis cisterna
removal of Man
medial cisterna
removal of Man and addition o GlcNAc
trans cisterna
addition of Gal, addition of NANA
trans Golgi Network
Sorting - sulfation of tyrosines and carbhydrates
Class A Genetic Defect
Accumulation of secreted proteins in the cytosol
Class B Genetic Defect
Accumulation of secreted proteins in the rough ER
Class C Genetic Defect
Accumulation of ER to Golgi transport vesicles
Class D Genetic Defect
Accumulation of secreted proteins in the Golgi
Class E Genetic Defect
Accumulation of secreted proteins in secretory vesicles
Scaffold proteins
from tethers which help keep vesicles and cisternae in place
Lysosomes
an organelle in the cytoplasm of eukaryotic cells containing degradative enzymes enclosed in a membrane
How are lysosomes activated?
by H+ pumps
How are the membranes of lysosomes protected from the acid hydrolases?
the membranes are glycosylated
What is the plant equivalent to a lysosome?
Vacuoles
What are the 3 pathways that deliver materials to lysosomes?
ednocytosis, phagocytosis, autophagy
Phagocytosis
engulf and digest external materials
Autophagy
destroy internal cell structures
Endocytosis
internalize and process membrane-bound materials
What is the purpose of Mannose-6-phosphate?
directs proteins to lysosomes
Pinocytosis
the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane
What happens once the Early Endosome becomes Acidified?
It forms the Late Endosome
Lipid Rafts
subdomains of the plasma membrane that contain high concentrations of cholesterol and glycosphingolipids
Trancytosis
transcellular transport in which various macromolecules are transported across the interior of a cell
What are the steps of receptor mediated endocytosis?
LDL particle binds to LDL receptors on the external surface of the cell, membrane buds into a clathrin coated vesicle containing the LDL inside the cell, the Vesicle becomes uncoated and fuses with the endosome and becomes the early endosome, endosome passes LDL to lysosome, transport vesicle buds off and returns to plasma membrane
How many cholesterol molecules does LDL contain?
1500