1.3 Intermediate Filaments and Cell Polarity Flashcards by Darren Zhou

Where are intermediate filaments found (2)?

in vertebrates, nematodes and mollusks
in cytoplasm of cells prone to mechanical stress

How well did you know this?

Not at all

Perfectly

Where are intermediate filaments not found?

animals that have rigid exoskeletons

How well did you know this?

Not at all

Perfectly

Intermediate filaments do not use [ ], unlike actin and tubulin.

NTPs

How well did you know this?

Not at all

Perfectly

Intermediate filaments (IF) are closely related to [ ].

nuclear lamins

How well did you know this?

Not at all

Perfectly

What is the function of nuclear lamins?

form meshwork in nuclear envelope, and provide anchoring point for chromosomes

How well did you know this?

Not at all

Perfectly

Nuclear lamins duplicated, and duplicates evolved into [ ].

rope-like IF

How well did you know this?

Not at all

Perfectly

IF are much more [ ] than actin and tubulin.

diverse

How well did you know this?

Not at all

Perfectly

IF proteins are encoded by [ ] different genes in humans, with functions specific to cell type.

How well did you know this?

Not at all

Perfectly

All intermediate filaments are [ ].

elongated proteins

How well did you know this?

Not at all

Perfectly

Conserved [ ] domain.

central alpha-helical domain

How well did you know this?

Not at all

Perfectly

Parallel dimers used to form [ ].

anti-parallel tetramer

How well did you know this?

Not at all

Perfectly

Tetramer lacks [ ] (both ends are the [ ]), unlike actin and tubulin.

polarity
same

How well did you know this?

Not at all

Perfectly

[ ] stack laterally to form the filament. Held together through [ ] interactions.

Eight
hydrophobic

How well did you know this?

Not at all

Perfectly

Intermediate filaments are very [ ].

flexible, stable and difficult to break

How well did you know this?

Not at all

Perfectly

What is the most diverse type of IF proteins?

keratin

How well did you know this?

Not at all

Perfectly

[ ] found in human genome. Approximately [ ] types of keratins in human epithelial cells. Approximately [ ] specific to hair and nail cells.

How well did you know this?

Not at all

Perfectly

Keratin filaments are [ ] of type 1 and type 2 keratin proteins.

equal proportion

How well did you know this?

Not at all

Perfectly

What are the characteristics of type 1 and type 2 keratin?

Type 1 keratin: acidic
Type 2 keratin: neutral/basic

How well did you know this?

Not at all

Perfectly

Type 1 and 2 form a [ ] used to make filaments.

heterodimer subunit

How well did you know this?

Not at all

Perfectly

Keratin filament networks are cross-linked via [ ].

disulfide bonds

How well did you know this?

Not at all

Perfectly

[ ] makes the filament networks very strong, and survive death of the cell

cross-linking

How well did you know this?

Not at all

Perfectly

Keratin filaments impart strength on these specialized epithelial cells by anchoring intermediate filaments at the sites called [ ].

desmosomes and hemidesmosomes.

How well did you know this?

Not at all

Perfectly

What site type are desomosomes and hemidesmosomes?

desmosomes: site of cell-cell contact
site of cell-matrix contact

How well did you know this?

Not at all

Perfectly

What is filaggrin?

accessory protein that bundles keratin filaments in outermost layers of the skin. Imparts greater toughness in the outer layer

How well did you know this?

Not at all

Perfectly

Individuals with filaggrin mutations are predisposed to [ ].

eczema

What is epidermolysis bullosa simplex?

caused by keratin mutations, slightest mechanical stress ruptures basal cells and produces blisters

Where are neurofilaments found?

in high concentration in axons of vertebrate neurons

What are the three types of neurofilaments?

1. NF-L 2. NF-M 3. NF-H

What is ALS (3)?

* amyotrophic lateral sclerosis (ALS) also known as Loug Gehrig's disease * associated with an abnormal assembly of neurofilaments in motor neuron cell bodies and axon * degeneration of axons leads to muscle atrophy and death

In mouse model, ALS symptoms arise with [ ].

overexpression of NF-L or NF-H

What are plakins?

linker proteins that connect intermediate filaments to other cytoskeletal structures

What are plectin?

a type of plakin protein that links intermediate filaments to microtubules, actin filaments, and myosin filaments, and the plasma membrane

Plectin and other plakins interact with [ ] that connect the cytoskeleton to the nuclear envelope.

protein complexes

The protein complexes consist of [ ] proteins and [ ] proteins.

1. SUN 2. KASH

Where are the SUN and KASH proteins located?

1. SUN proteins are in the inner nuclear membrane 2. KASH proteins are in the outer nuclear membrane

SUN and KASH proteins bind to each other in the [ ].

lumen of nuclear envelope

SUN and KASH connect the [ ] and [ ].

nuclear and cytoplasmic cytoskeletons

SUN proteins bind to [ ].

nuclear lamina or chromosomes

KASH proteins bind to [ ].

actin filaments (directly) and microtubules and IF (indirectly through motor proteins and plaskins, respectively)

The linkage between cytoplasmic and nuclear cytoskeleton facilitates [ ] (3).

1. chromosome movement during meiosis 2. nuclear migration 3. cytoskeletal organization

What is cell polarity?

refers to the asymmetry of a cell's structure and organization

Cell polarity determines [ ] (3).

1. direction of protein secretion 2. signaling, orientation of cell division 3. path of migration

Cells polarize in response to [ ].

intracellular and extracellular cues

Cytoskeleton acts to transduce [ ] and generate [ ].

1. polarity signals 2. cellular organization and behavior

What are the Rho family of proteins (3)?

1. Cdc42 2. Rac 3. Rho

What are Rho family proteins?

monomeric GTPases that act as molecular switches. They cycle between active GTP-bound and inactive GDP-bound state

[ ] determine the active state of the rho family of proteins.

regulatory proteins

What are GEFs?

guanine nucleotide exchange factors. required to activate GTPases by GDP with GTP

What are GAPs?

GTPase activating proteins. The inactivate GTPases by promoting hydrolysis of GTP

What are GDIs?

guanine nucleotide dissociation inhibitors. Bind to GDP-bound forms and block GTP exchange by GEF proteins

Active Cdc42 promotes [ ].

formation of filopodia on cell surface

Rac promotes [ ].

actin polymerization at cell periphery, and sheet-like protrusions

Rho promotes [ ].

bundling of myosin filaments in stress fibers of non-muscle cells

[ ] is most highly conserved and often serves as a master regulatory of cell polarity.

Cdc42

Clusters of Cdc42 transmits a signal that activates a protein called [ ].

formin

Formin causes the assembly of [ ].

actin filaments

What is the function of PAR proteins?

generate anterior-posterior polarity

Stationary cells [ ] polarity over the life of the cell.

maintain

Cell migration requires [ ] polarity.

dynamic

Polarization also allows for protrusion of [ ], which is driven through [ ].

1. leading edge 2. nucleation of branced actin filaments

Rac promotes the formation of [ ].

branched actin networks in lamellidodium

Rho promotes [ ].

the formin-dependent nucleation and elongation of staight actin filaments

Rock leads to [ ] and activates [ ].

1. downstream inactivation of an actin-destabilizing protein 2. myosin. Along with actin bundle formation, this increases contractility at the rear of the cell

External signals can drive the process of cell migration via [ ].

chemotaxis

What is chemotaxis?

the movement of a cell towards or away from a diffusible chemical source

[ ] triggers Rho family proteins.

ligand binding at the receptor

Neutrophils can detect [ ] which enables them to migrate towrads bacterial targets.

low concentrations of select diffusible peptides derived from bacterial proteins