Intermediate FIlaments

length of intermediate filaments

about 10 nm

keratins

a water soluble intermediate filament that aids in abrasion resistance in the cell

-in epithelia

4 major classes of intermediate filaments

keratins, vimentin (or vimentin related), neurofilaments, and nuclear lamens

cytoplasmic intermediate filaments

keratins, vimentin, and neurofilaments

nuclear intermediate filaments (nuclear lamins)

-in all animal cells

-help maintain the integrity of the nuclear envelope

vimentin/ vimentin related

in connective tissue, muscle cells, and neuroglial cells

-hold tissues together

keratin is found in

epithelial: skin, hair, nails

-hold skin cells together

neurofilaments

in nerve cells

-support nerve cell shape

how many classes of intermediate filaments can be expressed in each cell type?

one or 2

a single intermediate filament is always made of _____ of subunit

the same type

does IF require ATP or GTP?

no

nuclear lamina is consistently found in

nuclei

structure of IFs

monomers create polymers

-large central region (alpha helix)

-unique head and tail specific to its type that are important for functionality

assembly of the IFs

two monomers form a dimer

-dimers allign antiparallel, forming a tetramer

-staggered arrangement leads to a ropelike structure that aids in stabilllity

why dont IFs require an energy source?

they exhibit a self-assembly property, allowing them to spontaneously form unlike the other two types

the alpha helix in IF arrangement is a key to protein forming because

the amino acids that stick out will determine what can bind/ if the material can be in aqueous solutions or not

Nuclear laminas job during interphase

it aids in the organization of the chromatin in the nucleus

-chromosomes get anchored to the lamina allowing for gene expression

-also linked to the cytoskeleton and increases structural organization

what is triggered when lamins are phosphorylated at the beginning of mitosis?

it triggers them to depolymerize, breaking down the nuclear envelope which is important for cell division

at the end of anaphase, lamins will dephosphorylate, causing

the reformation of the lamina, bringing the envelope and chromosomes back to starting position

Hutchinson-Gilford Progeria Syndrome

a mutation in a lamin protein that causes rapid aging in children

Emery-Dreifuss muscular dystrophy

the mutation of genes encoding nuclear lamins, depleting cell health

desmosomes (binding body)

large proteins plaques in the plasma membrane that attaches adjacent cells and anchor to the basal lamina forming hemidesmosomes

+facilitate cell to cell adhesion

desmosomes are ____ and found on the ____

localized, lateral sides of the plasma membrane

hemidesmosomes

like desmosomes but they use integrins in the extracellular space and link basal sides to the lamina lucida

components of hemidesmosomes

1. integrin (linker proteins)

2. desmoplakin (intracellular attachment proteins)

3. keratin in epithelial cells, Desmin in heart cells ( intermediate filaments)

transmembrane linker proteins

integrin

epidermolysis bullosa

painful skin blisters and tears caused by mutations of keratin (skin attachment)

-there is no cure

pemphigus vulgaris

an autoimmune disorder where antibodies attack desmoglein, disrupting the integrity of desmosomes causing blisters on the scalp and back