Lecture 12: Endocytosis Flashcards by Tami Ojewole

clathrin

from TGN forward and PM backward

How well did you know this?

Not at all

Perfectly

COPI

golgi stack backward

How well did you know this?

Not at all

Perfectly

COPII

ER forward

How well did you know this?

Not at all

Perfectly

endocytosis critical for maintaining ____

cardiovascular health

How well did you know this?

Not at all

Perfectly

endocytosis (clathrin-dependent transport) hijacked by ___

many viruses for entry in cell

How well did you know this?

Not at all

Perfectly

clathrin was the 1st ___ due to ___

coat protein discovered due to unique structure and number in cell (a lot)

How well did you know this?

Not at all

Perfectly

similarities between COPI and clathrin due to convergent evolution

-triskelia (3 structure)
-similar cage shape

How well did you know this?

Not at all

Perfectly

COPI, COPII, clathrin are ___

similar in size

How well did you know this?

Not at all

Perfectly

method used to determine structure of COPI, COPII, clathrin

X-ray crystal structures

How well did you know this?

Not at all

Perfectly

COPI coats combine ___

features of clathrin + COPII

How well did you know this?

Not at all

Perfectly

COPI and COPII similarities

-similar assembly unit

How well did you know this?

Not at all

Perfectly

clathrin are made of ____ chains that assemble into ___

heavy and light chains
triskelions

How well did you know this?

Not at all

Perfectly

clathrin assembly in cages ___

happens spontaneously

How well did you know this?

Not at all

Perfectly

clathrin ____ membrane into vesicles

deforms

How well did you know this?

Not at all

Perfectly

clathrin interacts with _____

adaptor protein

How well did you know this?

Not at all

Perfectly

uncoating of clathrin vesicles requires ___

energy; driven by ATP hydrolysis (Hsp70 and auxlin)

How well did you know this?

Not at all

Perfectly

Hsp70 is a chaperone that ____

binds to newly syn. proteins and uses ATP (involved in uncoating clathrin vesicles

How well did you know this?

Not at all

Perfectly

clathrin interacts with adaptor protein with ___

its heavy chain

How well did you know this?

Not at all

Perfectly

adaptor proteins that interact with clathrin

-AP-1, AP-2, GGA

How well did you know this?

Not at all

Perfectly

adaptors link ____ to clathrin

cargo

How well did you know this?

Not at all

Perfectly

assembly of clathrin cycle

-adaptor protein binds to cargo/cargo receptor in cytoplasm
-clathrin binds to adaptor protein : forming bud
-clathrin triskeleton forms as vesicles forms + membrane bending and fision proteins form vesicles
-coated vesicle is uncoated with ATP (Hsp70 +auxlin): removal of clathrin + adaptor proteins so vesicle can bind to target membrane

How well did you know this?

Not at all

Perfectly

for clathrin transport< soluble proteins ____

require receptors for connection adaptor proteins

How well did you know this?

Not at all

Perfectly

4 properties of clathrin adaptors (required + optional)

Bind cargo
Bind clathrin
Bind phospholipids (PIP2) (optional)
Bind accesory proteins (optional)

How well did you know this?

Not at all

Perfectly

the use of specific adaptor depends on _____ and ___

intracellualr site
sorting signal

How well did you know this?

Not at all

Perfectly

clathrin transport: TGN to endosome adaptor proteins

-GGA -AP-1

clathrin transport: endosome to TGN adaptor proteins

-AP-1

clathrin transport: PM to endosome adaptor proteins

-AP-2

endocytosis occurs in _____ rich regions of PM

-phosphatidylinositol 4,5-bisphosphate (PIP2)

TGN membrane rich with ___ which acts as velcro

PIP

different phosphoinositides bind to ___

different adaptors

AP-1 are ____ made ______ subunits

heterotetramers made of beta (β),gamma (γ) , mu (µ), lowercase sigma (σ)subunits

subunit size of AP-1 (biggest to smallest)

-beta (β),gamma (γ), -mu (µ), -lowercase sigma (σ)

-beta (β),gamma (γ) subunits of AP-1 are made of ____

ears/appendanges, hinges, trunk

AP-1 has binding sites for ___

clathrin + cargo

cargo binding to AP-1 needs which motifs + which subunits bind?

LL (B) and YXXO (µ)

retrival of M6PR from endsomes to TGN and sorting of M6PR from TGN to endosomes need which adaptor protein in CCVs?

-AP-1

For binding to AP-1, cargo without LL binds to ___

µ subunit via YXXO motif

GGA stands for

(Golgi-localized g-ear-containing ARF-binding protein)

GGA are ____ adaptors that link clathrin to cargo in _____

monomeric modular adaptors that link clathrin to cargo in an ARFdependent (GTPase) manner

GGA are responsible for sorting M6PRs from ___

TGN to endosomes

GGA bind to M6PR with motif ___

DXXLL

GGA requires ___ to bind to cargo

GTP

AP-2 functions at ____

AP-2 is ___ adaptor protein

heterotetramer

subunits of AP-2

α,β2,µ2, σ2

α subunit of AP-2 binds to _____

amphiphysin, EPS15 + others

β2 subunit of AP-2 binds to _____

clathrin (appendages) and di-leuicine (body)

µ2 subunit of AP-2 binds to ___

YXXO motif

amphiphysin, EPS15 + others are ___

accessory proteins that regulate assembly

AP-2 has ___ -binding domains

clathrin,acessory protein,cargo, PIP2

Binding of ____ on membrane induces conformational change in AP2 that ___

PIP2 that exposes cargo binding sites (ap2 locked to ap2 open)

assembly of clathrin coats at PM

-recruitment of nucleating proteins (FCHO1/2) that create membrane curves at domains rich with PIP2 -Intersectin and EPS15 link FCHO protein to AP2 that links to clathrin

FCHO1/2 are ___ proteins that induce ____ at ____

nucleating membrane curvature PM domains rich with PIP2

FCHO1, 2 are _____ proteins that bind to and bend membranes (--- charged)

BAR domain-containing (++++ charged)

FCHO1, 2 then bind scaffold proteins _____that link it to ____

-Eps15 and Intersectin -AP2 complexes

CCVs creation at PM

-recruitment of FCHO, EPS15, intersection >membrane curvature -AP2 recruited and bind to cargo -clahtrin recuited by AP2 -GTPase activity by Dynamin for vesicle scission -auxilin incorporated into triskelion structure and recruit Hsp 70 (ATP hydrolysis)- uncoating

ATP hydrolysis by ___ (with auxilin) drives uncoating of CCVS

Hsp70

auxilin incorporated into ___

structure of clathrin triskelia

dynasore (def.)

small molecule that blocks dynamin function

endocytosis motifs are similar to ____

lysosomal sorting motifs

endocytosis motifs

-tyrosine based (NPXY & YXXO) -dileucine (LL), phsophoserine

clearing LDL from blood serum with endocyotsis

-LDL receptor + ligand binding promotes recruitment of receptor coated pits -vesicles uncoated and forms endosomes -lysosome forms and LDL is broken down -at neutral pH, endosome releases receptor to bind to another LDL particle

Genetic mutations in LDL receptor gene (1/500) _____can lead to increased risk ____

lacking targeting domain (no LL, tyrosine motif) of heart attack due to atherosclerosis

true or false: all ligands are degraded after endocytosis

false

example or ligand that isn't degraded after endocytosis

Ferrotransferrin (ligand + iron) binds to transferrin receptor --> CCV --> uncoating --> low PH release iron from ligand but ligand still bound to receptor) --> ligand (apotransferrin) retained and recycled to surface, ligand released at neutral pH

scission of coated vesicles driven by ___

GTP hydrolysis

Dynamin is a ___

gtp-ase

mutation in or near GTPase domain of dynamin lead to ____

blocking of scission of CCVs from PM

dynamin works at ___

dynamin has mutliple functional domains

-GTPase domain (4 domains together) -PHD domain -PRD domain -GED domain

GTPase domain of dynamin does what?

-hydrolyzes GTP

PHD domain of dynamin does what?

binds to PIP2 (inositiol phospholipids)/acidic phospholipids in PM

PRD domain of dynamin does what?

binds to proteins with SH3 domains like amphiphysin

GED domain of dynamin does what?

has GAP function activates GTPase increase rate of GTP hydrolysis

mutation in GTPase domain of dynamin does what?

decrease endocytosis

mutation in PHD domain of dynamin does what?

decrease endocytosis

mutation in GED domain of dynamin does what?

increase endocytosis

mutation in PRD domain of dynamin does what?

blocks endocytosis

GTPase activity of dynamin in different forms

-very active (2-100 GTP)- rings, collars -increase 100-1000x at necks of coated vesicles, spiral form

GTP hydrolysis results in pitch change of dynamin spirals and promotes ____

scission

amphiphysin is ____

a link between CC PIT and dynamin through AP2

FCHO, AP2, Clathrin, Amphiphysin, dynamin, EPS15, Intersectin interactions

FCHO to Intersectin /EPS15 to AP2 to clathrin AP2 to Amphiphysin to dynamin

domain of Amphiphysin that links to AP-2

CLAP

domain of Amphiphysin that links to dynamin

SH3 domain to PRD domain of dynamin

regulatory view of dynamin

Oligomerization and increased GTPase activity inhibits endocytosis --> GTP bound dynamin controls effectors that mediate vesicle formation

mechanochemical view of dynamin

GTP hydrolysis and conformational change in dynamin are required for endocytosis

Unifying model for dynamin mechanism

originally in regulatory form (tetrametric) (slow GTP hydrolysis) then mechanochemical (spiral) form (fast GTP hydrolysis)

Switch between functional states of dynamin regulated by ____

SH3 domain containing binding partners (ex. amphiphysin) that sense critical events in CCV maturation

______ of dynamin controls rate-limiting step in endocytosis (CCVs formation)

slow form of GTPase (tetramer)

mutation in GTPase domain of dynamin keeps____

dynamin in rate-limit step longer increasing endocytosis

Lecture 12: Endocytosis Flashcards

(90 cards)