Actin and Myosin in Non-skeletal muscle cells Flashcards
What are 5 examples of actin and myosin in non skeletal muscle cells
Cytokinesis
Smooth muscle
Vesicle transport
Cytoplasmic streaming
cell migration
What is seen in contractile rings
Actin myosin orginzation is seen in contractile rings gets smaller smaller by de polymerizing
Where is smooth muscle contraction present
Arteries and intestines and is not voulntary
What is relaxation
When the myosin is folded and inactive
How does Calcium play a role in smooth muscle contraction
When it is present it activates a kinase CaM which goes to phosphorylate Myosin light chain that will activate myosin heavy chain that can now hold onto the actin
What a regulator of smooth muscle contraction
Myosin phosphorylation
Whats the difference between smooth muscle contraction and skeletal muscle
Smooth muscle is much slower and more persistent contaction than skeletal muscle also there is no troponin and tropmyosin so it can last for much longer
What are Myosin V bound vesicles
They are carried along actin fillaments
When is myosin v unactive
When there is no cargo
Why do you want the nucleus to be close to the bud
Because half of its DNA goes into the daughter cell
What is the actin doing in a yeast buding cell
It provides a pathway that leads into the bud
what transports structures get into the bud
Myosin 5
What capps the actin
Formin
What postions the nucleus
MT
Which way is the actin polymerzing
It is growing in the negative end so the positive end stays in the bud
Where does cytoplasmic streaming occur
Usually occurs in plant cells and helps with difuusion can occur in us but not for diffusion
What filopodia formation
Finger like projections from bundles
What is lamellipodia formation
Large movement of actin pushed from networks
How do membranes move forward
Because the actin is polymerzing
What are fochal adhesions
Serve as anchoring points for actin filaments providing structural support and enabling cells to respond to their enviorment
What are integrins
Involves trans membrane proteins
What does Cyclo and cAMP do on the cell surface
Tell s the cell where to go and moves the cell to a high concentration
What is a receptor
It is around the entire cell because the cell has to know where to go
Where is the direction going to go
Towards high concentration
What happens when the ligand binds
Binds to the receptor which then turn activates the associated G protien
Where is actin and mysoin on the cell
Actin is in the front form the lamellipodium pushes it forward and myosin is in the back stress fibers that push the back of the cell forward
What are the 4 steps of cell movement
Step one which is extension you have a stress fiber inbetween each focal adhesion
the actin polymerizes and the membrane will extend
Step 2 the new adhestion is formed along with a new stress fiber
Step 3 It then translocates forward actin and myosin interact with each other and move the cell body forward
Step 4 is de-adhesion is where you really move the cell bringing th ehead and tail forward
What is Cdc42 rac and rho
They are all RHo protiens which is memebrs of the RAS superfamily of small GTPASE
What do GTP in active form trigger
Effecteor protiens
What happens if you have a dominant active Rac
The whole membrane ruffle lamellipodia at one
What happens if you have dominant Cdc42
Lots of fillpodium made
What happens if you have domminant active RHO
Activate formin causes unbranched actin get long acting bundles that are SF
What does Cdc 42
Works with wasp and then that activates Arp23 which creates actin polymerization and then
What does Cdc42 do once it is activated
It is activated first and then go to activate rac GTP
What does Rac GTP activate
Goes to turn on WAVE then Arp 2/3 and actin polymerization to form lamellipodia
What does Rho GTP activate
Formin which causes actin polymerization that makes stress fiber formation and contraction also activates Myosin
What Rho protien contributes to polarity
Cdc42
Are they the same in migratory and non migarotry cells
In migaratory cells they have a sighlty different function
How many do you need to work together
3
What happens if you have Cdc42 activation at the front
Leads to front activation of rac leading to arp 2/3 activation and Roh back is leading to myosin 2 activation
What are functions of intermediate filaments
- Not globular
No Atp or GTP needed
No polarity
No known motor protiens
Less dynamic
Tetramer is the basic sub unit
What are the types of intermediate epithelia cells
Acidic keratins and basic kertains
Contribute to tissue strength and intergrity
What are class 3 of intermediate fillaments
Desmin are intergrity to muscle celss striated and smooth
Vimentin found in migrating cells and mesenchymal cells
What is class 4 of intermediate filaments
Neurofilaments
Found in neurons
Structure to axons
What is class five of intermediate filaments
Lamins
Not cell type specific
Provides support to the nucleus
Inter membrane is filled with them
What are the point of intermediate fillaments
They are organizational protiens microtubules link to them and the have protiens that can bind to them and hold them in place provide structural support for cell shape
What does vimetin do
Links to aankyrin at plasma membrane
What do Lamins A b and C do
Support the nuclear membrane
What are B lamins
Ubiquitous and linked via prenylation
What state are IFs in
They are in a dynamic state
What happens when something polymerizes
Cells need to regualte and get rid of the nuclear membrane have to get rid of lamina A
How does lamin disasemble
N terminal domain of lamin A phosphorylated at serine and prevents reassbley if the serien residue mutated no disassembly
What is lamina A for
The nuclear membrane if you want to go under mitosis it has to disassemble
What are IFs crucial too
What type of tissue
Epithelia and other tissue integrity this is why the skin does not break
What holds the epidermis and dermis together
Kertain
What do transgenic mice carrying a mutant kertain gene exhibt
Skin blistering
What are desmosomes
Cell to cell adhesions that are supported by keartain
What are hemidesmoses
Cell to extracellular matrix
What are the 4 types of cell adhesions
Tight junctions
Gap junctions
Cell-cell adhesions
Cell- ECM adhesions
What are tight junctions
Not bound to the cytoskeltons so they do not contribute srength they restrict what basses between cells
You want to make sure that material does not go through the cell and sneak in between
What are the three types of tight junctions
JAM
Occludin
Caludin
What are gap junctions
What are they formed by
Also do not contribute to stength
Formed by 6 connexins to form a connexon
Small molecules such as ions can flow through these chanels
Different molecules pass through dependent on what type of conexon
Channels between adjacent cells
What happens when you damage one cell
You have to close the gap junction
What is gap junctions dependent on
Ca concentration if the cells is damages because there is not alot of Ca inside the cell normally
What are Ig superfamily of CAMS
Cell-cells adhesion
Homophilic interacations are the same molecules
What are homophilic interacations
Same molecules and it is cell to cell Cadherins and Ig superfamily (Cams)
What are heterophilic interacations
two different molecules binding together example Intergrins and selectins
What is the Ig superfamily
Mediate Ca independent (bind cells together independent of Ca) homophilic adhesion same tissue will have the same superfamily so they can stick together
What are Major cadherin molecules
What types of tissues
Single transmembrane domain and cytosolic C terminal tail associated with the cytoskeleton
Ca dependent
Need the extracellular calcium
Essisental for holding cells in sheets
Epidermal tissues
Nervous tissues
How to tell the difference
If you remove calcium and it still binds it is a superfamily need the same one ot bind cells together
What are cadherins dependent on
Other than calcium
Cytoskeletal elements the cytopplasmic domain interacts with the cytoskeletal and depends on what part of the cytoskelton it binds to
What will it do if it binds to a IF like keratin
Form a desmosome
what will form if cadherin binds to binds to F actin
Adheren junctions can form a belt and become contractile also for cell movement
What does F actin do
Comes together to form the circumferential belt that can become contractile
Why do celladhesions link to the cytoskeleton
To allow signaling cells will know if they are linked to each other or not this will single to cell nucleus if things are broken
What is the extra cellular matrix
Mix of secreted molecules that all cells interact with and regulates many cellular functions
what are the functions of ECM
- Anchorning and surriounding cells to maintain soild tissue
- Determening the biomechanical properties of the extracellular enviornment
- Controlling cellular polarity survival proliferation differntiation and fate
- Inhibitng or facilitating cell migration
- Binding to and acting as a reservoir of growth factors
- Activating cell surface signaling receptors
What are ECM protiens
Hydrophilic Proteoglycans (which absorbs water and tissue resilency) structural adhesive and special cell surface protiens
What does alpha 1 beta 1 bind to
collagen
What does alpha 5 and Beta one bind to
fibronectin
What does alpha 6 and beta 1 bind to
laminin
What is a heterodimer
Many alpha and beta combination
What makes focal adhesions
When fibronectin binds to the intergins
Can a cell be migartory and non migartory
NO it can not bind to make stress fibers and focahal adhesions and lamina and kertain at the same time
What does a cell migrating need
Fibronectin needs alpha 5 beta one is lamepodiulia locking to bring intergrins when binds it will form a fochal adhesion and stress fiber for cell migration
What happens when an integrin is bent
Can not bind to ECM
When can intergrin be active
Partially active when when one is extended and closed fully active when it is extended and open
What do intergrins do
Promote molecules in cell migration
What do selectins recognize
Oligosachaccarides
What are the steps of leukocyte extravasation
- Leukocyte is in resting state
Alpha L beta 2 intergrin attached
And selecting ligand which are specefic carbohydrated
PAF receptor
On the molecule you have ICAM
This is to the endothelial cell which lines bloods vessels and regulates exchange between the bloodstream and surrounding tissues
Vesicle containg P-selectin
Resting state when there is no bacteria
Step 2
Endothelial activation and leukocyte attachment and rolling
Usually not bound wants to leave so it rolls around
The bacteria causes release of the P-selectin which binds to the selectin ligand (sugars)
Step 3
Leukocyte activation
PAF activates intergrin
Starts rolling around finally binds to the pAF receptor binds to PAF
This activates the integrins
It is because once it binds to PAF it activates integrins
Step 4
Firm adhesion via integrin/ICAM binding
ICAM stops the rolling
The integrigs can bind to ICAM
Cell to cell adhesion
Step 5
Extravasation
Leukocyte squeezes between endothelial cell as it moves from the blood into the tissue
P selectin is being secreted
In presence of infection you want to secret it
Strong binding pushes it in between
