Cytoskeleton (4-6) Flashcards
highly dynamic and play
comparably diverse and important roles in the cell
Microtubules
Microtubules are polymers of the protein ?
tubulin
heterodimer formed from two closely related globular proteins called α-tubulin
and β-tubulin
tubulin
two tubulin proteins are
found only in this heterodimer
α-tubulin
and β-tubulin
has a binding site for
one molecule of GTP
α-tubulin and β-tubulin
Tubulin is found in all ____ cells
eukaryotic cells
give rise to a paralytic eye-movement disorder due to loss of ocular nerve function
mutations in human β-tubulin gene
mutations in a particular human β-tubulin gene
give rise to a
paralytic eye-movement
hollow cylindrical structure built from 13
parallel protofilaments
microtubule
microtubule is built from
13 parallel protofilaments
Each 13 parallel protofilaments of microtubule, composed of a?
αβ-tubulin heterodimers stacked head to tail and then folded into a
tube
along the longitudinal axis of microtubule
protein-protein contact
forms an interface with the “bottom” of the α-tubulin
molecule in the adjacent heterodimer
“top” of β-tubulin molecule
the main lateral contacts
α–α and β–β
the addition and loss of subunit occurs almost
exclusively at the
end
The subunits in each protofilament in a microtubule all point in the same?
direction
the subunits in each protofilament in a
microtubule all point in the same direction
structural polarity
exposed at the minus end
α-tubulins
exposed at the plus end
β-tubulins
influenced by the binding
and hydrolysis of GTP
microtubules dynamics
microtubules dynamics is influenced by the
binding and hydrolysis of GTP
occurs only within β-tubulin
GTP hydrolysis
bound GTP
“T form”
bound GDP
“D form”
two different types of microtubule structures
T form
D form
____- ____ tends to polymerize and ____-____ to
depolymerize
GTP tubulin
GDP-tubulin
whether the tubulin subunits at the very end of a microtubule are in the T or the D form depends on
the relative rates of
GTP hydrolysis and tubulin
addition
If the rate of subunit addition is high, the tip of the polymer remains
in the _ form
T form
tip of the polymer remains
in the T form forms a
GTP cap
an end might grow for a certain length of time in a _ form, but then suddenly change to the _ form and
begin to shrink rapidly
T
D
rapid interconversion between a growing
and shrinking state
dynamic instability
growth to shrinkage
catastrophe
shrinkage to growth
rescue
produce straight
protofilaments that make strong and regular lateral contacts with one another
tubulins subunits with GTP bound to the
β-monomer
tubulins subunits with GTP bound to the β-monomer produce?
straight protofilaments
associated with subtle conformational change in
the protein
hydrolysis of GTP to GDP
subtle conformational change in the protein, makes the protofilaments?
curved
constrain the curvature of the protofilaments, the ends appear straight
GTP cap
terminal subunits have hydrolyzed
constrains is removed, spring apart
2 polymer drugs that inhibit the microtubule functions
polymer-stabilizing and polymer destabilizing drugs
interact with tubulin subunits and lead to
microtubule depolymerization
colchicine and nocodazole
binds to and stabilized
microtubules
Taxol
Taxol binds to and stabilizes microtubules, causing a net increase in
tubulin polymerization
used to treat cancers of
the breast and lungs
Taxol
Microtubule drugs that preferentially kill dividing cells
microtubule-depolymerizing and
polymerizing drugs
______ ___ _____ _____ required for spontaneous nucleation of
microtubules is very high
concentration of tubulin subunits
smaller amounts, involved in the nucleation of microtubule growth
γ-tubulin
Microtubules are generally
nucleated from a specific intracellular location known as a
microtubule-organizing center (MTOC)
two accessory proteins bind directly to the γ-tubulin, along with several other proteins
that help create a spiral ring of γ-tubulin
molecules, which serves as a template
that creates a microtubule with 13
protofilaments
γ-tubulin ring complex
two accessory proteins bind directly to the
γ-tubulin, along with several other proteins
accessory proteins bind directly to the γ-tubulin, along with several other proteins that help create a
spiral ring of γ-tubulin
molecules
spiral ring of γ-tubulin
molecules, which serves as a
template
that creates a microtubule with 13
protofilaments
well-defined MTOC, which is located near the nucleus
centrosome
well-defined MTOC called the centrosome,
which is located near the nucleus and from which ______are nucleated at their minus ends, so the plus ends point outward and continuously grow and
shrink
microtubules
embedded in the centrosome; a pair
of cylindrical structures arranged at right angles
in an L-shaped configuration; barrel shape with
striking ninefold symmetry
centrioles
centrioles, a pair of cylindrical structures arranged at
right angles
in an L-shaped configuration
centrioles are embedded in the
centrosome
where microtubule nucleation takes place
pericentriolar material
MTOC embedded in
the nuclear envelope found in budding
yeast, fungi, and diatoms
spindle pole body
no centrioles in
fungi or plants
all these cells use this to nucleate their microtubules
γ-tubulin
with dynamic plus ends pointing outward toward the cell periphery and stable minus ends collected near the nucleus
aster-like configuration
aster-like configuration of microtubules is robust,
with dynamic plus ends pointing
outward toward the cell periphery and stable
minus ends collected near the nucleus
has the ability
to find the center of the cell established
a general coordinate systems
microtubule cytoskeleton
microtubule cytoskeleton has the ability
to find the center of the cell established
a general coordinate systems, which is then used to
position many organelles within the cell
exhibit much higher polymerization rate, a greater catastrophe frequency, and extended pauses in microtubule
growth
microtubules in cell
microtubules in cell exhibit?
- much higher polymerization rate,
- a greater catastrophe frequency, and
- extended pauses in microtubule growth
modulate filament dynamics and
organization
microtubule-binding proteins
proteins that bind to microtubules
microtubule-associated proteins (MAPs)
can stabilize microtubules against disassembly
microtubule-associated proteins (MAPs)
mediate interactions with other cell components – prominent in neurons,
axons and dendrites that extend from the
cell body
MAPs
MAPs are prominent in
neurons, axons and dendrites that extend from the cell body
MAPs have at least __ ___that binds to the
microtubule surface and another that projects outward.
one domain
long projecting domain; form bundles of stable microtubules that are
widely spaced
MAP2
shorter projecting domain, form bundles of more closely packed
microtubules
tau
are targets of several protein kinases
MAPs
influence stability and dynamics
proteins that bind the ends of microtubule
rate at which a microtubule switches from growing to a shrinking state
frequency of catastrophe
rate at which a microtubule switches from shrinking to
growing state
frequency of rescues
bind to
microtubule ends and appear to pry
protofilaments apart
catastrophe factors (kinesin-13)
protects microtubule
minus ends from the effects of
catastrophe factors
Nezha / Patronin
enriched at microtubule plus
ends; binds free tubulin subunits and
delivers them to the plus end; promoting
microtubule polymerization and
simultaneously counteracting catastrophe
factor activity
XMAP215
stabilized by association with
a capping protein or the centrosome;
depolymerization sites
minus ends
explore and probe the entire
cell space
plus ends
accumulate at these active ends (+) and
appear to rocket around the cells as
passengers at the ends of rapidly growing
microtubules; dissociating from the ends
when microtubules shrink
plus-end tracking proteins (+TIPs)
behave as +TIPs and act to modulate the growth and
shrinkage of microtubule
kinesin-related catastrophe factors and
XMAP215
control microtubule positionin
kinesin-related catastrophe factors and
XMAP215
(Other +TIPs)
small dimeric proteins; attach to the
plus end; allow the cell to harness the
energy of polymerization; used for
positioning the spindle, chromosomes, or
organelles
EB1
unpolymerized tubulin subunits to
maintain a pool of active subunits
cell sequester
binds to two tubulin
heterodimers and prevents their addition to the
ends of microtubules; decrease the effective
concentration of tubulin subunits
stathmin (Op18)
inhibits its binding to
tubulin
stathmin phosphorylation
“sword”; made up for two subunits,
smaller ones hydrolyze ATP performs the actual
severing, larger on directs katanin to the
centrosome
katanin
microtubules also use _____ proteins to
transport cargo and perform a variety of
other functions
motor proteins
two types of motor proteins
kinesins and dyneins
kinesin-1 is alsi called
conventional kinesin
carriers membrane-enclosed organelles away from the cell body toward the axon terminal by walking toward the plus end of microtubule
kinesin-1 (“conventional kinesin”)
Kinesin-1 is similar to
myosin II in having two heavy chains per active motor
is the common element of myosin and kinesin
motor domain
How many distinct families in kinesin superfamily
14
Most of fourteen distinct families in the kinesin superfamily have the?
motor domain at the N-terminus of the heavy chain and walk toward the plus end of the microtubule.
uses the ATP hydrolysis to depolymerize microtubule ends
motor domain
has a central motor domain and does not walk at all, but uses the
energy of ATP hydrolysis to depolymerize microtubule ends
kinesin-13
have a binding site in the tail for another microtubule
Most kinesins
instead of the rocking of a lever arm, small movements at the nucleotide-binding site regulate the docking and undocking of the motor head domain to a long linker region.
kinesin-1
docking and undocking of the motor head
domain to a long linker region acts to throw the
second head forward to a binding site 8 nm closer to the microtubule plus end,
closely coordinated, so that this cycle of linker
docking and undocking allows the two-headed motor to move in a hand-over-hand (or head-over-head) stepwise manner
nucleotide-hydrolysis cycles
allows the two-headed motor to move in a hand-over-hand stepwise manner
cycle of linker docking and undocking
family of minus-end directed microtubule motors unrelated to the kinesins
dyneins
dyneins are composed of
one, two, or three heavy chains (that include
the motor domain) and a large and variable number of associated intermediate,
light-intermediate, and light chains
two major branches of dynein family
cytoplasmic dyneins (first branch)
Axonemal dyneins (second branch)
homodimers of two heavy chains
cytoplasmic dyneins
used for organelle and mRNA trafficking, for positioning the centrosome and nucleus during cell migration, and for construction of the microtubule
spindle
cytoplasmic dynein I
have cilia and is used to transport material from the tip to the base
of the cilia
Cytoplasmic dynein 2
highly specialized for the rapid and efficient sliding movements of microtubules that drive the beating of cilia and flagella
axonemal dyneins (ciliary dyneins)
the largest of the known molecular motors,
Dyneins
follows the general rule of coupling nucleotide
hydrolysis to microtubule binding and unbinding as well as to a force-generating
conformational change
dynein motor
major function of cytoskeletal motors in interphase cells
transport and positioning of membrane-enclosed organelles
Kinesin was originally identified as the
protein responsible for fast anterograde axonal transport
movements toward the cell’s periphery
antegrade axonal transport
identified as the motor responsible for
transport in the opposite direction, retrograde axonal transport
Cytoplasmic dynein
movement towards the cell center
retrograde axonal transport
require the action of minus-end directed cytoplasmic dynein
centripetal movements toward the cell center
centripetal movements toward the cell center require the action of
minus-end directed cytoplasmic dynein
require plus-end directed kinesin motors
centrifugal movements toward the periphery
centrifugal movements toward the periphery require
plus-end directed kinesin motors
tubules aligns with microtubules and extends almost to the edge of the cell
ER
near cell center
Golgi apparatus
large protein complex associated to
cytoplasmic dynein to translocate organelles
effectively
dynactin
dynactin is large protein complex associated to
cytoplasmic dynein
short, actin-like filament that forms the actin-related Arp1
dynactin complex
dynactin is actin-like filament that forms actin-related
Arp1
Have been linked to neurological diseases
defects in microtubule-based transport
cells fail to migrate
to the cerebral cortex of the developing brain
smooth brain (lissencephaly)
a dynein-binding protein required for nuclear migration in several species
Lis1
resulting in nuclear-migration
defects where nuclei migrating neurons fail to attach to dynein
absence of Lis1
regulate the activity of motor proteins = ?
changes in the positioning of its membrane-enclosed organelles or whole-cell
movements.
contain large pigment
granules that can alter their location in response to neuronal or hormonal stimulation
fish melanocytes
assembly depends on reorganization of
the interphase array of microtubules to
form bipolar array of microtubules
mitotic spindle
mitotic spindle assembly depends on
reorganization of the interphase array of microtubules
neuronal cytoskeleton
- dendrites
- axons
receive signals; mixed
polarities of microtubules
dendrites
transmit signals; minus end
pointing back toward the cell body, the
plus end pointing toward the axon
terminals
axons
are filled with bundles of microtubules
axon and dendrites
are highly specialized
and efficient motility structures built from
microtubules and dynein
cilia and flagella
cilia and flagella are built from
microtubules and dynein
hairlike cell appendages that have a bundle of microtubules at their core
cilia and flagella
found on sperm and many
protozoa
flagella
By flagella’s undulating motion, they enable
the cells to which they are attached to ?
swim through liquid media
beat with a whiplike motion that
resembles the breaststroke in swimming
cilia
The movement of a cilium or a flagellum is produced by the bending of its
core, which is called the
axoneme
composed of microtubules and their
associated proteins, arranged in a
distinctive and regular pattern
axoneme
axoneme is composed of?
microtubules and their associated proteins
arranged in a ring around a pair of single
microtubules
nine special doublet microtubules
form bridges
between the neighboring doublet
microtubules around the circumference
of the axoneme
axonemal dynein
hereditary defects in axonemal dynein
causes?
primary ciliary dyskinesia or
Kartagener’s syndrome
primary ciliary dyskinesia or Kartagener’s syndrome is characterized by
sinus inversus
due to disruption of fluid
flow in the embryo; male sterility due to
immotile sperm; high susceptibility to lung
infections due to paralyzed cilia
sinus inversus
sinus inversus is due to
disruption of fluid
flow in the embryo; male sterility due to
immotile sperm; high susceptibility to lung
infections due to paralyzed cilia
bacterial flagella
flagellin
nonmotile counterpart of cilia and flagella
primary cilium
can be viewed as specialized cellular compartment or organelles
Primary cilia
Primary cilia shares
structural features with
motile cilia
nine groups of fused fused
triplet microtubules arranged in a
cartwheel
centriole
are found on the surface of almost all cell types, where they sense
and respond to the exterior environment
Primary cilia
in the nasal epithelium
odorant reception and signal amplification
converting light to neural signal
rod and cone cells of retina
forms a cytoplasmic filament
intermediate filament
prominent in the cytoplasm of cells that are subject to mechanical stress
intermediate filament
intermediate filament are enerally not found in animals that have
rigid exoskeletons
elongated proteins with a conserved central α-helical domain containing 40 or so heptad repeat motifs that form an extended coiled-coil structure with another monomer
all intermediate filament family members
all intermediate filament family members are elongated proteins with a conserved central?
α-helical domain
associates in an antiparallel fashion to
form a staggered tetramer
a pair of parallel dimers
a pair of parallel dimers associates in an antiparallel fashion to
form a
staggered tetramer
do not
contain a binding site for a nucleotide
intermediate filament
do not contain a binding site for a
nucleotide; two ends are ____ ___
the same
pack together laterally to
form the filament, which includes eight
parallel protofilaments made up of
tetramers
tetramers
tetramers pack together laterally to
form the filament, which includes
eight
parallel protofilaments made up of
tetramers
Each individual intermediate filament therefore has a cross section of
32 individual α-helical coils
ropelike character; easily bent, but
are extremely difficult to break and
can be stretched
intermediate filaments
the most diverse intermediate
filament family
keratins
Every keratin filament is made up of an equal mixture of
type I (acidic) and type II (neutral/basic) keratin proteins
type I (acidic) and type II (neutral/basic) keratin proteins form a
heterodimer
can survive even the death of their cells
Cross-linked keratin networks
held together by disulfide bonds
clinically useful in the diagnosis of epithelial
cancers (carcinomas)
diversity in keratins
may produce multiple
types of keratins, and these copolymerize
into a single network
a single epithelial cell
cell-cell contact
desmosomes
cell-matrix contact
hemidesmosomes
defective keratins in the basal cell
layer of the epidermis
epidermolysis bullosa complex
epidermolysis bullosa complex, in which the ____ ____, in response to even very slight mechanical stress, which ruptures the basal
cells
skin blisters
Other types of blistering diseases
disorders of the mouth, esophageal
lining, cornea of the eye
typified by cell rupture as a
consequence of mechanical trauma
and a disorganization or clumping of
the keratin filament cytoskeleton
epidermolysis bullosa complex
found in high
concentrations along axons
neurofilaments
Three types of neurofilament proteins coassemble in vivo, forming heteropolymers
NF-L, NF-M, NF-H
NF-L, NF-M, and NF-H coassemble in vivo forming
heteropolymers
new neurofilament subunits are incorporated all along the axon in a dynamic process that
involves the addition of subunits along the filament length as well as the ends during?
axonal growth
seems to directly control axonal
diameter, which in turn influences how
fast electrical signals travel down the
axon
level of neurofilament gene expression
neurodegenerative disease associated with an accumulation and abnormal assembly
of neurofilaments in motor neuron cell bodies and in the axon
amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease)
third family of intermediate filaments
vimentin-like filaments
expressed in skeletal, cardiac,
and smooth muscle, where it forms a
scaffold around the Z disc of the
sarcomere
Desmin
Desmin is expressed in
skeletal, cardiac, and smooth muscle
Desmin is expressed in skeletal, cardiac, and smooth muscle, where it forms a scaffold around the
Z disc of the sarcomere
muscle-cell abnormalities (misaligned muscle fibers)
mice lacking desmin
In humans, mutations in desmin are associated with various forms of
muscular dystrophy and
cardiac myopathy
In humans, mutations in desmin are associated with various forms of muscular dystrophy and cardiac myopathy, illustrating the important role of desmin in
stabilizing muscle fibers
scaffolds for proteins
that control myriad cellular processes
including transcription, chromatin
organization, and signal transduction
A-type lamins
A-type lamins are scaffolds for proteins that control myriad cellular processes including
transcription, chromatin
organization, and signal transduction
are associated with mutant versions of lamin A and include tissue-specific diseases
laminopathies
linked to the rest of the cytoskeleton
by members of a family of proteins
called plakins.
intermediate filament network
The intermediate filament network is
linked to the rest of the cytoskeleton
by members of a family of proteins
called
plakins
large and modular,
containing multiple domains that connect cytoskeletal filaments to each other
and to junctional complexes
Plakins
Plakins contain multiple domains that connect
cytoskeletal filaments to each other
and to junctional complexes
can interact
with protein complexes that connect
the cytoskeleton to the nuclear interior
Plectin and other plakins
Plectin and other plakins can interact
with protein complexes that connect
the cytoskeleton to the
nuclear interior
serve as an additional filament system in all
eukaryotes except terrestrial plants
septins
Septins assemble into nonpolar filaments
that form
ring and cagelike structures
Septins assemble into nonpolar filaments
that form rings and cagelike structures, which act as
- scaffolds to compartmentalize
membranes into distinct domains - or recruit and organize the actin and
microtubule cytoskeletons
septin filaments localize to the neck between a
dividing yeast
mother cell and its growing bud
block the movement of proteins from one side of the bud neck to the other
septins
Septins also recruit the
actin–myosin machinery
actin–myosin machinery forms
the contractile ring required for
cytokinesis
In animal cells, septins function in
cell division, migration, vesicle
trafficking
septin filaments serves as a ______ _____ in primary cilia
diffusion barrier
How many septin genes in humans
13
relies on the
coordinated deployment of the
components and processes
cell migration
cells move by
crawling
crawl continuously in search of food
amoebae
In animals, almost all cell locomotion occurs by crawling, with the notable exception of
swimming sperm
During ______, the structure of an animal is created by the migrations of individual cells to
specific target locations
embryogenesis
During embryogenesis, the structure of an animal is created by the
migrations of individual cells to
specific target locations
In vertebrates, they are remarkable
for their long-distance migrations from their site of origin in the neural tube to a
variety of sites throughout the embryo
neural crest cells
fundamental to the construction of the entire nervous system
Long-distance crawling
crawl to sites of infection and engulf foreign invaders
macrophages and neutrophils
bone remodeling and renewal
osteoclasts
migrate through connective
tissues
fibroblast
travel up the sides of the intestinal villi, replacing absorptive cells
lost at the tip of the villus
cells in the epithelial lining
cell crawling also has a role in many
cancers
complex process that depends on the actin-rich cortex beneath the plasma membrane
Cell migration
Cell migration is a complex process that depends on the
actin-rich cortex
beneath the plasma membrane
Three distinct activities involved in Cell migration
protrusion
attachment
traction
plasma membrane is pushed
out at the front of the cell
protrusion
cytoskeleton connects
across the plasma membrane to the
substratum
attachment
the bulk of the trailing cytoplasm
is drawn forward
traction
relies on forces generated by
actin polymerization
protrusion
are filled with dense
cores of filamentous actin
protrusive structures
formed by migrating growth
cones of neurons and some type of
fibroblast; one-dimensional; contain a core
of long, bundled actin filaments
Filopodia
formed by epithelial cells
and fibroblast; two-dimensional sheetlike
structures; contain a cross-linked mesh of
actin filaments
Lamellipodia
actin-rich
protrusion; three-dimensional; important for
cells to cross tissue barriers
invadopodia and podosomes
depends on hydrostatic pressure
within the cell; generated by the
contraction of actin and myosin
blebbing
well studied in the epithelial cells of the epidermis of fish and frogs
Lamellipodia
epithelial cells of the fish and frogs are known as
keratocytes
epithelial cells of the fish and frogs are known as keratocytes because of their abundant ___ ___
keratin filaments
cover the animal by forming an epithelial
sheet and specialized to close wounds
epithelial cell
epithelial cells cover the animal by forming an?
epithelial sheet
assume a distinctive shape with a very large lamellipodium and a small, trailing
cell body that is not attached to the substratum when cultured as individual cells
keratocytes
crawl forward
lamellipodia
remain stationary with
respect to the substratum
actin filaments
plus ends facing forward
actin filaments
minus ends of actin filaments are frequently attached to the sides of other actin filaments by
Arp 2/3 complexes
are attached to the sides of
other actin filaments by Arp2/3
complexes helping to form the two-dimensional web
minus ends
assembling at the front and disassembling at the back
the web as a whole is undergoing
treadmilling
localized at the leading edge
filament nucleation
filament depolymerization occurs at sites
located well behind the
leading edge
occurs at sites
located well behind the leading edge
filament depolymerization
binds preferentially to actin filaments
containing ADP-actin; new T-form filaments
generated at the leading edge resistant to
depolymerization
cofilin
filaments generated at the
leading edge should be resistant to depolymerization by cofilin
new T-form filaments
can efficiently disassemble the older
filaments
cofilin
for the leading edge of a migrating cell to
advance, _____ __ ___ _____ must be
followed by adhesion to the substratum at the front
protrusion of the membrane
in order for the cell body to follow, contraction
must be coupled with
de-adhesion at the rear
of the cell
processes contributing to migration are therefore tightly regulated in space
and time, with ?
actin polymerization, dynamic adhesions, and myosin contraction
operates in at least two ways
to assist cell migration
Myosin II
first way of Myosin II to assist cell migration
helping to connect the actin cytoskeleton to
the substratum through integrin-mediated adhesions
dynamic assemblies of
structural and signaling proteins
focal adhesions
second way of Myosin II to assist cell migration
bipolar myosin II filaments, which associate with the
actin filaments at the rear of the lamellipodium
and pull them into a new orientation
associate with the actin filaments at the rear of the lamellipodium and pull them into a new orientation
bipolar myosin II filaments
disengaged interaction between actin network and focal adhesions, polymerization pressure at the leading edge and myosin-dependent contraction cause the actin network to slip back
retrograde-flow
cause the actin network to slip
back
polymerization pressure at the
leading edge and myosin-dependent
contraction
retrograde-flow disengaged interaction
between
actin network and focal adhesions
the front end of the cell remain structurally and functionally distinct from the back end
cell migration
takes the form of the establishment of cell
polarity
cytoskeletal coordination
required
for oriented cell divisions in tissues and
for formation of a coherent, organized
multicellular structure
cell polarization processes
depends on the local regulation of actin
cytoskeleton by external signals
establishment of cell polarity
monomeric GTPases that
are members of the Rho protein family
Cdc42, Rac, and Rho
act as molecular switches
Rho proteins
Its activation on the inner surface of the plasma membrane triggers actin
polymerization and bundling to form filopodia
Rho –Cdc42
Activation of Rho –Cdc42 form ?
filopodia
Its activationp romotes actin
polymerization at the cell periphery, leading to the formation of sheetlike lamellipodial extensions
Rac
Rac forms?
sheetlike
lamellipodial extensions
Promotes both bundling of actin filaments with myosin II filaments into stress fibers and clustering of integrins and associated
proteins to form focal adhesions
Rho
Activation of Rho promotes both the?
bundling of actin filaments with
myosin II filaments into stress fibers and clustering of integrins and associated
proteins to form focal adhesions
members of the WASp protein family
activated Cdc42
severe form of immunodeficiency in which immune system cells have abnormal
actin-based motility and platelets do not form normally
Wiskott-Aldrich Syndrome
activates WASp family
members
Rac-GTP
activates the
cross-linking activity of the gel-forming protein filamin and inhibits the contractile activity of the motor protein myosin II.
Rac-GTP
Aside from activating WASp family members, Rac-GTP activates the cross-linking activity of
the ___-_____ _____ ____&_
gel-forming protein filamin
Rho-GTP activates a protein kinase that
indirectly inhibits the activity of cofilin, leading to
actin filament stabilization
turns on formin proteins to
construct parallel actin bundles
Rho-GTP
inhibits a phosphatase acting on myosin light chains
protein kinase activated by Rho-GTP
the movement of a cell
toward or away from a source of
some diffusible chemical
chemotaxis
Chemotaxis act through ____ family proteins to set up large-scale cell polarity
Rho family proteins
chemotactic movement of a class of white
blood cells toward a source of bacterial infection
neutrophils
enable them to detect very low
concentrations of N-formylated
peptides derived from bacterial
proteins
Receptor proteins on the surface of neutrophils
Receptor proteins on the surface of neutrophils enable them to detect very low
concentrations of
N-formylated peptides
binding of chemoattractant to its
GPCR activates
phosphoinositide 3-kinases (PI3Ks)
activates PI3Ks
binding of chemoattractant to its
GPCR
Activation of phosphoinositide 3-kinases generate what signaling molecule?
[PI(3,4,5)P3]
Generation of signaling molecule [PI(3,4,5)P3] activates the
Rac GTPase
after activation of Rac GTPase, Rac then activates the
Arp 2/3 complex
activation of the Arp 2/3 complex leads to
lamellipodial protrusion
binding of chemoattractant to its receptor activates another signaling pathway
that turns on ___ and enhances ____-____ _____
Rho
myosin-based contractility
two processes directly inhibit each other, such that ?
Rac activation dominates in the front of the
cell and Rho activation dominates in the rear
Rac activation dominates in the front of the
cell and Rho activation dominates in the rear enables the cell to maintain its
functional polarity
