Epithelium: Cytoskeleton Flashcards
In the intestinal microvilli…Identify
What type of epithelia is present
left to right
Line 1
Line 2
Ciliated Columnar
Brush border
Goblet Cell
Intestine
Identify (left to right)
Line 1
Line 2
LIne 3
LIne 4
Bottom third
Left to right
Line 1
Line 2
Cap
Intestinal microvillus
Actin Bundle
Glycocalyx
Actinf ilament rootlets
Terminal Web
Microvilli and sterocillia have what type of core?
F-Actin
where are microvili found?
In the small intestine-brushborder (columnar)
and the kidney-nephron (cuboidal)
Microvilli serve what purpose?
to increase the absorbative surface
What protien is seen inside the cap of microvilli?
Formin(caps the barbed end)
promotes the enlongation of unbranched f-actin
How wide is f-actin?
7um
What are the actin cross linking protiens found in microvilli?
Villin
fimbrin
both stablize the actin bundle
What are the membrane linking protiens found in microvilil?
myson I and Calmodulin
What purpose does Glycocalyx serve and where is it found?
It is a plasma memebrane coat of enzymes which breakdown protien and carbohydrates during absorbtion (small intestine)
The terminal web is seen at the base of …
and what does it consist of?
Microvilli
it consist of IF and spectrin
What are the affects of cytochalsins on F-actin?
Where is it found
bind to fast growing end (+) (caps it)
prevent addition of G-actin
Found in Fungi (alkoloids)
What are the effects of Phalloidin on F-actin?
It binds to actin filaments preventing their depolarization
foudn in mushrooms (alkoloid)
What are the effects of Latroneulins on F-actin?
Binds to G actin and induces F -actin depolarization
In microfilements Polymerzation is dependant on what?
ATP
Occurs at (+) barbed end
Profilin is a…
ADP-ATP Exchanger seen at the barbed end
promotes the transfer of actin monomers from thymosin to the barbed end of the actin filament
regulates filament assembly
Gelsolin…
Severing/capping protien
binds to the newly formed plus end
Blocks further polymerization
Cofilin
Actin depolymzerzation factor
stimulates the dissasocation of ADP bound B actin
What is treadmilling?
Steps of Treadmilling
The balence between polymerization and depolymerization of F-actin
Pointed ends grow less rapidly then the barbed ends
Steps
- Thymosin (sequesters G actin into reserve pool)
- Profilin binds to G-actin (goes from ADP to ATP)
- GTP-Actin binds to the barbed end (+)
- Once attached ATP hydrolyized to ADP-actin
- Cofillin (stimulates the disassocation of GDP-Actin from pointed end (-).
WASP is seen where?
What does it do?
In F-actin
it is a branching protien (activates ATP for branching)
Works with Arp 2/3(actin related protien) to branch
WAS is due to a defect in
WASP
low latelet count
immunodeficiency
respiratory infections
F-Actin
Made out of..
Depend on what for assembly?
Moter protiens
State
G-actin
ATP-dependant
Double helical and BRanching
Treadmilling
Myosin Va/vIia (muscle contraction)
Actin filaments (microfilaments) are involved in ..
cell motility…and cargo stransport
Microtubles are involved in…
cell motility and cargo transport
intermediate filaments provide
mechanical strength
skin support
stability
Direct immunoflorescence
Adv
Disadv
adv: direct attachment of de to primary antibody
faster
disadv
less senstiive then indirect
Indirect immunofluorescence
Adv: uses two antibodies (more specfic)
Disadv: complex..time consuming
Limitations of Immunofluorescence Microscropy
- photobleaching
- limited to fixed cells/tissues (dead)
If uses Green fluorescent protien (jelly fish) can use of live
Identify type of cytoskelteon from left to right
Intermediat fil (10)
Microtubles (25)
Actinfilament bundle (7)
Where are intermediate filaments found?
throughout the cytoplasm
surround the nucleus
extending out to the cell peripherty
anchored to cell junctions (SPOT desmosomes)-connect to adjacent epithelial cells
Anchored to hemidesmosomes-connect epithelial cell to ECM
nuclear lamina
How are intermediate filaments formed?
1Monomer
- dimer (parallel arangment)
- tetramer (antiparallel arrangment +side by side)
- protofilament (tetramers align end to end)
- protofibril (protofilaments align side by side)
- intermeidate filaments (8 protofibrils wind up_
What does phosphorylation do to Intermediate filaments?
diassemble
What does dephosphorylation do to IF?
promote assembly
Classification of IF
I/II
III
IV
V
IV
I/II- epithelial cells..keratins
III- mesenchymal derived cells
vimentin (fibroblast, smooth muscle, WBC)
Desmin ( muscle cells)
IV- Neurofilaments
V-Nuclear Lamins (A,B,C)
found in eukaryotic cells/ part of nucleus
VI- nestin (neurons)
embroynic development of stem cells
Epidermolysis Bullosa Simples (EBS)…
defect in keratin
cant form strong IF
weak
blisters after minor trauma
Excessive Keratinzation
skin becomes cracked for fragmented
Keratin provides…to epithelial cells
mechanical strength
Nuclear Lamina is associated to…
inner nuclear membrane
What are the only organelles surround by a double membrane?
Mitocondria and Nucleus
Nuclear Lamina contains
Lamins (type V IF)
Lamins..
are connected to the inner and outer membranes of the nuclear envelope by several protiens
Lamins are divided into Type A and Type B lamins
describe
Type A: lamin A and C (derived from single gene LMNA)
Type B: Lamin B encoded by two genes LMNB1 AND LMNB2
LAMINS ARE EXPOSED TO CHROMATIN IN THE INNER MEMBRANE
Structural alterations of Lamins …
impact integrity of the nucleus
nuclear fragility
decrease of gene expression
eventual nuclear destruction
Laminopathies
Progeria (premature aging) LMNA gene
repture of the nuclear envelope and release of chromatin
Emery-Drifuss Muscular Dystrophy Emerin deficiency
Greenberg skeletal dysplasia LBR defc
Microtubules are composed of
tublin dimers which polymerize in the presence of GTP
Microtubules main function
cell division …and cargo transport
Describe the structure of microtubules
long and hollow tubues of protiens
beta tublin is exposed at the the (+) end faster gorwing end
alpha tublin is exposed at the (-) end sower growing end
dynamically unstable: rapidly assemble in one site and disassemble in another site
results from
hydrolysis of GTP-tublin dimers , releeased of hydrolyzed phosophate and subsequen release of GDP-tublin subunits
Microtubules grow out from
Centrosomes
Microtubule motor protiens
Kinesin (anterograde)
dynein (retrograde)
Microtubules can form transient and permenant structures..
transient: miotic spindle
cytoplasmic MTs diassemble and then reassemble to form the mitotic sspindle( separates chromsomes equally into two daughter cells)
Permenant
Axoneme of cilia (9+2)
Flagella sperm
Microtubule associated protiens (MAPs)
facilitate assembly and prevent diassembly
Centrosome
Function as microtubule orangizing center
minus ends of hte microtubules are anchored
Types of microtubless (3)
kinetochore
Polar
Astrial (radiating)
Mitotic Center (centrosome)
Microtuble organizing center
centrioles (2)
Radiating microtubules/ astrial (extend outward to cell periphery)
Mitotic apparatus
centrosome (mitotic center)
+
spindle
Mitotic spndle
kinetechore microtubules (assembles on centromere)
+
Polar microtubules (overlap with one another in the center of the cell..not attached to chromosomes)
repsonsible for separation of daughter chromosomes
Centrosome
MT organizing center
Main protien (gamma tubulin)
Minus ends of MT anchored to centrosome
plus end grows away
Consist of
2 Centrioles (perpendicular orientation to one another)
(9+0)
surrounded by amorphous pericentriolar material
centriole generates basal bodies(forms cilia and flagella)
Vocabulary
Kinetochore
complex of protiens assembled on centromeric DNA during mitosis and meisosic
(dot on centromere)
the asembly of the kinetechore depends ont he presence of centromeric DNA Sequences
Vocabulary
Centromere
chromosomal site where the kinetochore assembles
narrow chromatin region on metaphase chromosomes
primary constiriction
Antimitotic Drugs
Colchicine
TOXIC NOT USED IN TREATMENT OF TUMORS
used for gout
forms a complex with tubulin dimers and copolmerizes into the microtubule lattic
Antimitotic Drugs
Vinblastine
binds to the plus end of ictrotubles to suppress MT dyamics
Treat: lymphomas (lymph and spleen tumors)
Antimitotic Drugs
Paclitaxel/ Taxol
binds on inside of microtubule prevents its depolymerization
Treats: breat and ovarian cancer
Microtubule arrangement
Cilia
Basal Body
Cilia - (9+2) axoneme
Basal Body (9+0) same as centrioles
How are basal bodies attached to the cytoplasm?
Through straited rootlets
Moter Protiens Microtubules
Dynein
Dynein/dynactin
move chromosomes along kinetochore microtubules as microtubules shorten at hte kinetochore byt he loss of GDP-tubulin
Bardet-Biedil syndrome (BBS)
defective intraciliary and intraflagellar transport of axonemal protien
issue with dynein and kinesin
Clincial Correlates
age related retinal dystrophy
obesitiy
polydactyly (extra fingers)
renal malfucntion
reproductive tract abnormalities
learning disabilities
Cilia
protect the surface of epithelia from pathrogens (resp tract)
motile
mobilization of cells (oviduct-egg transport/ efferent ductules of epiddymis-sperm transport)
Primary Cilium
immotile
speicalized antenna_collects info from ECM to trigger cell signaling
modified primary cillia ( kinocilium-ear,haircells/ phtoreceptor cells-retina)
(Dsykinesia)
Defects in primary cilia formation
Left-right axis malformation
Situs inversus-heart on right side intestinal malrotation
this is because primary cilia generate a direction flow gradient of regulartory molecules (morphogens) to dictate correct organ development during embryogenesis
Function of hte inner sheath and radio spokes
stablization of axonemal bending
Issue with axonal transport
kartenger syndrome
movement
cilia vs. flagella
cillia-power stroke
flagella-sinsoidal movement
Myosin I
(unconventional myosin)foudn in all cell types
one head domain and a tail
single light chain
interacts with actin filaments and contains ATPase
transports vesicle of organelles
smaller then myosin II
dont form dimers
Myosin II
(conventional myosin)
Present in muscle and non musucle cells
identical molecules
ATPase containing head domain longg rodlike tail
Muscle contraction
Myosin V
(unconventional)
double head with ATPase
RAb27a
vesicle receptor
