Cytoskeleton Flashcards
What are the functions of the cytoskeleton?
- Maintains shape of cells
- Moves intracelular traffic
- Pulls chromosomes apart in mitosis
What are the 3 types of filament in the cell from smallest to largest?
- Microfilaments (7-9nm)
- Intermediate filaments (10nm)
- Microtubules (25nm)
What are microfilaments also known as?
Actin filaments
- Polymers of actin
What filament are microvilli formed by?
Microfilaments (actin filaments)
What is the basic unit of the muscle fibre?
Sarcomere
What 3 main structures make up the sarcomere?
Actin and associated proteins
- Thin filament
Myosin
- Thick filament
Z disc
- Contains vimentin and desmin
What happens when myosin filaments slide past actin?
Contraction
What is the main function of intermediate filaments?
Maintain cell shape / structure
How can intermediate filaments help in cancer diagnosis?
Used as tumour markers
What is immunohistochemical staining?
Antibodies are directed against intermediate filament proteins
- Specific filaments will be associated with certain tumour types
- Stain will show whether antibody binds
- Positive stain will suggest tumour origin/type
What tissues are derived from mesenchymal tissue?
- Connective/soft tissue
- Fibroblasts
- Skeletal muscle
- Mesothelium lining of perineum, synovial joints
- Endothelium
- Adipocytes
- Osteoblasts
Vimentin is found in what types of tissue?
Mesenchymal tissue
What does the z disc contain?
Vimentin and desmin
What are sarcomas?
Cancers of mesenchymal origin
What tissue marker will sarcomas be +ve for?
Vimentin
Leiomyosarcoma is a cancer of what tissue?
SM
Liposarcoma is a cancer of what tissue?
Adipocytes
What non-sarcoma tumors will be vimentin +ve?
- RCC
- Meningioma
- Endometrial carcinoma
What part of the sarcomere can act as a tumor marker for muscle tumors?
Desmin
What sarcomas may have a desmin +ve tumor?
- Rhabdomyosarcoma
- Leiomyoma
- Leiomyosarcoma
Epithelial tumours most commonly have what tumour marker?
Keratin
- Cytokeratin
What part of the cell do lamins (intermediate filament) form?
Nuclear envelope
- Contians outer and inner membrane with an intermembrane space
What is a laminin?
Extracellular protein
- DIFFERENT FROM A LAMIN which forms the nuclear membrane
Where are neurofilaments found?
Neurons (especially axons)
What tumours may have a +ve neurofilament dtaining?
CNS tumors
- Neurobalstoma
- Medulloblastoma
- Retinoblastoma
What are GFAP (glial fibrillary acidic proteins) found in?
- Atrocytes (mainly)
- other CNS glial cells (not neurons)
What CNS tumours may have a positive GFAP marker?
- Astrocytoma
- Glioblastoma
What makes up a microtubule?
Alpha and Beta tubulin
- They polymerize into a long ‘protofilament’
- Each dimer has 2 GTP
Which GTP can be hydrolyzed on the microtubule?
Beta GTP
- The alpha tubulin is simply part of the struacture and therefore cannot be used for energy
Where do microtubules grow from on the cell?
Centrosome near nucleus
- Emanate a star pattern on the cell
Where is the negative and positive end of the MTs?
- Positive ends are at periphery
- Negative end is at centrosome
What is dynamic instability in relation to MTs?
Where microtubules grow slowly yet can rapidly disassemble (~ 100 times faster)
What are the MT motor proteins called?
Dynein and kinesin
What MT motor protein carries things away from the nucleus, towards +ve end?
Kinesin
What MT motor protein carries tthings toward negative end?
Dynein
What MT motor protein is responisble for the localization of the golgi apparatus near the cell centre?
Dynein
What 2 motility structures are built from MTs and dynein?
Cilia and flagella
How are axonemes arranged?
Found in cilia and flagella
9x2 pattern
- 9 doublet MTs in a ring
- Surround a pair (2) MTs
What are the cilia and flagella secured by?
Basal body
- 9 groups of fused triplets of microtubules (no central pair)
How do the cilia and flagella move?
- Through axonemal dynein: forms bridges between MTs
- Activated dyenein pulls on neighbouring doublets
- Sliding of doublets -> bending of cilia/flagella
What does cilia and flagella need to activate dynein and therefore move?
ATP (MT dependent ATPase)
Primary cilia dyskinesia (PCD) is due gene mutations coding for what?
Dynein
Primary ciliary dyskinesia (mutated dynein) results in what?
- Rhinosinusitis -> pneumonia
- Infertility
What is Kartagener’s syndrome? (the triad of symptoms, associated with PCD)
- Chronic sinusitis
- Bronchiectasis (chronic cough, recurrent infections)
- Situs inversus
What is the mitotic spindle made up of?
MTs
What cancer drugs inhibit MTs?
- Vincristine, vinblastine (inhibit polymerisation)
- Paclitaxel (enhance polymerisation, block breakdown)
How does colchicine inhibit MTs?
Prevents MT assembly
- Disrupts chemotaxis, generation of cytokines, phagocytosis
What anti-gout medication prevents MT assembly?
Colchicine
What ant-fungal drug inhibits MTs?
Griseofulvin
What ant-helminth medication inhibits MTs?
Mebendazole
