Cytoskeleton Flashcards
What are actin filaments made from?
Actin polymer
What are microtubules made of?
Alpha-beta tubulin dimers
What are intermediate filaments made from?
Intermediate filament proteins
What acin polymerises into F-actin?
G-actin
How many other subunits does F-actin contact ?
Three, along the strand and between the two strands
Structure of mysoin
- Myosin (class 2) is a hexameric protein:
- Two heavy chains dimerise (via the coiled coil) to form the coiled-coil tail
and two globular myosin heads - Each myosin head is composed of a motor domain and a lever.
- The lever contains 2 ‘IQ’ motifs (IQxxxRGxxR)
- Light chains bind to the IQ motifs – two per lever (two per heavy chain)
- Essential light chain (ELC) binds to an IQ motif close to the motor
- Regulatory light chain (RLC) binds to the IQ motif close to the coiled coil
Hypertrophic cardiomyopathy (HCM)
Autosomal dominant, typical missense mutations in genes encoding sarcomeric proteins. Left ventricular hypertrophy and myofibrillar disarray
Mutations in MYH7 cause what disease?
HCM
Mutations in MYBPC cause what disease?
HCM
Mutations in loop 1, converter and relay helix likely affect what?
Force generation
Mutations in S2 affect
Interacting heads motif, more ATP usage. Could affect binding of MyBPC
Mutations in non muscle myosin 2A cause these diseases
Blood clotting disorders, deafness and kidney disorder
What does the activation of platelets depends on?
NM2A and actin
What do smooth and non-muscle myosin 2 isoforms form?
10S shutdown state.
What are smooth and noon-muscle myosins activated by?
Phosphorylation of the RLC
Mutations in MYH9 cause what disorders?
Bleeding
Mutations in skeletal muscle actins can cause
Skeletal muscle myopathies
What mutations cause Baraitser-Winter syndrome?
Mutations in beta and gamma actins
Symptoms of Baraitser-Winter syndrome
Changes around the eyes: (congenital ptosis
(drooping eyelid),
* High-arched eyebrows,
* Hypertelorism (increased eye spacing),
* Missing tissue around the eye (Ocular colobomata)
* Brain malformation - anterior predominant
lissencephaly.
* May also be short
* May also have microcephaly, intellectual disability, seizures and hearing loss
What is critical to forming a highly folded brain?
Neuronal migration
What is important for neuronal migration?
Non muscle actins
Keratin is an example of what type of fibre?
Intermediate
What filaments are required for cell to cell and cell-ECM adhesion?
Intermediate
What happens in the skin epidermis basal layer?
Cells adhere to underlying extracellular
matrix through focal adhesions
(hemidesmosomes)
Cells divide (proliferate) - express K5
and K14
Then migrate upwards to spinous layer:
Switch keratin isoform expression to K1
and K10
Mutations in keratin 5 and 14 cause
Epidermolysis bullosa
mutations in Keratin 1 and 10 cause
Epidermolytic Hyperkeratosis
What is found at the fast growing end of microtubule tubes?
Beta-tubulin which hydrolyses GTP, can exchange GDP for GTP.
Do both alpha and beta tubulin bind GTP?
Yes
Does beta tubulin hydrolyse GTP?
Yes, only.
What part of microtubules can be PTM’ed?
C terminal tails
What are microtubules essential for?
Cell migration, cargo transport, mitosis and formation of synapses and neuronal cells.
What are the two types of motor proteins?
Kinesin and dynein
How many types of kinesin are there?
Many, about 40, some specialised for trafficking like Kif5 (kinesin-1).
How many types of dynein?
One, cytoplasmic.
Which end does kinesin-1 move on microtubules?
Plus end
Which end of microtubules does dynein move to?
Minus
Description of TUBA1A mutation derived disease
Cause microcephaly, developmental delay, epilepsy, lissencephaly (smooth brain).
What residue is commonly mutated in TUBA1A
R402
What cell type are microtubules critical for?
Neurones
What is KIF1A for?
Anterograde transport, veiscles for pre and post synaptic assmebly. Autophagy
What is KIF1C for?
Anterograde cargo transport and retrograde transport between Golgi and ER
What disease can Kif5A mutations cause?
Hereditary spastic paraplegia (SPG10), amytrophic lateral scleosis (ALS), Charcot-Tooth-Marie tyoe 2 (CMT2)
Exon 27 deletion leads to what?
Aggregation