Mitochondria, Cytoskeleton, & Cell Motility Flashcards
Mitochondria anatomy?
-bound by a double membrane surrounding a fluid-filled matrix
- inner membrane= cristae (has proteins that generate ATP)
- inner space= the matrix; contains enzymes that break down carbs
Mitochondria genetic composition?
-has ~1000 genes that combine to form the mitochondria, are a combo of nuclear and mitochondrial DNA
What is the function of the mitochondria?
- take raw material (fat, protein, glucose) and convert it into usable energy (ATP)
- power plant of the cell
What happens if mitochondria has faulty power production?-
=faulty cell function=problems with organ & tissue function
-leads to many human disorders
How do fats get into cells?
-via carnitine transports
CoQ10?
- an antioxidant, this and others are important in electron transport chain
- accept free radicals so don’t damage the cell
Mitochondria DNA inheritance?
- only from mom
- when cells divide, copies are inherited in each daughter cell randomly
- so each cell can have a unique mix of WT and mutant mito.
- called heteroplasmy
- if happens in utero, can have a mix of WT and mutant tissues/organs, but symptoms could manifest only in high energy organs
what do mitochondria disorders tend to effect? why?
- high energy using organs/ tissues
- because mito. makes ATP, mito fucked= less ATP= less energy to do work by those organs
- most commonly brain/CNS
heteroplasmy
- when an individual has a mix of healthy (wild type) and mutant alleles/ genes
- ex= mitochondria mutants
Mitochondrial mutations in siblings? Why?
- siblings can have same mutations, but have different organs affected and to various degrees
- because mito. get separated randomly during cell division
why test mtDNA mutations in blood not effective?
-because mtDNA can vary tissue to tissue, organ to organ, or blood to either. so can take blood sample and look healthy, but if tested live you’d find it
Mitochondria mutations change over time?
- yes, some mutations can get worse or better (slow accumulation of cell injury)
- depends on mitosis and distribution of mutant vs wild type mito. during cell division
-as get old=more mitosis=more risk of fucking it up=more chance of accumulating mito mutant in CNS and getting a debilitating disorder
How can we combat mito. disease?
-suggested to implant healthy mito. but hard since would need to get into correct cells/tissue and don’t always know how to determine that
Why is there a slow accumulation of cell injury in mito diseases?
- cuz if have a mix of WT and mutant DNA, the wt can partially compensate for the unhealthy mito so works decently
Mitochondrial diseases?
- 100s of diff. diseases genetically
- individuals w/ same mutation, can have diff. symptoms (even identical twins)
- diseases change over time makes hard to diagnose and hard to treat since most affect the CNS
What is the cytoskeleton? What does it do?
- a network of filaments & tubules that extend from the nucleus to the plasma membrane
1) cell structure/shape
2) attachment site for proteins
3) cell movement
what are the three elements of the cytoskeleton ?
1) actin (microfilaments) (7nm)
2) microtubules (25nm)
3) intermediate filaments (10nm)
roles in cell shape, movement within the cell, movement of the cell
microtubules structure & function?
small hollow, cylinders made of tubulin polymers (alpha & beta) dimerize, have 13 columns of tubulin
- 25nm diameter, 15nm hollow tube(lumen)
- maintenance of cell shape, cell motility, chromosome movements in cell division, organelle movements
microfilaments structure and function?
- made of 2 long actin filaments intertwined together
- actin=globluar (circular)
- 7nm long
- maintenance & changes of cell shape, muscle contraction, cell motility & division
intermediate filaments structure & function?
- 10 nm long
- fibrous keratin family proteins supercoiled into thick cables
- very stable, allows cells to withstand mechanical stretching (ex. skin)
1) anchors for nucleus& other organs
2) support plasma membrane & nuclear envelope
3) provide tensile strength in cell
what is tubulin?
- small globular protein used to make microtubules
- alpha and beta are made from it
How is microtubule assembly controlled?
by the microtubule organizing center, the centrosome
How microtubules move things in the cell? Why important?
- act as tracks that kinesin/kinesin receptors can walk along while carrying cargo vesicles
- microtubules=stationary, kinesin utilizes ATP hydrolysis to walk along the track
-important for neurons w/ long axons, when things need to get from cell body to the terminal synapse at end of neuron
microtubules and genetic disordrs
- genetic disorders can be associated w/ dysfunction in microtubules or the accessory proteins that help them (ex: kinesin)
- most diseases affect transport (especially in neurons)
what happens if lack intermediate filaments (keratin fam proteins)?
- cells wouldn’t be able to handle mechanical stretching such as with the skin and things could pop/burst
acidic and basic keratins location and function?
- intermediate filament class
- in epithelial cells
- involved in tissue strength & integrity
design, GFAP and vimentin location and function?
- intermediate filament class
- in muscle & glial cells
- function= sarcomere organizations & integrity
neurofilaments location and function?
- intermediate filament class
- found in neurons
- function= axon organization
Lamina location and function?
- intermediate filament class
- found in nucleus
- role in nuclear structure & organization
Genetic diseases due to intermediate filaments?
- mutant keratin genes lead to skin diseases that leave individual susceptible to skin damage
- death can occur during birth from this; or can just have unstable/weak skin
- EBS skin disease
- also damage to the neurofilaments can lead to loss of motor control like in ALS
-Epidermolysis bulls simplex (EBS)
- due to keratin (intermediate filament) mutations
- patients get blisters on skin from cell lysis (breaking) after minor trauma to skin
Actin filaments structure& function?
- occur in bundles/ mesh networks that have polarity
- have (+) end= BARBED
- have (-) end= POINTED
- filaments play structural role & involved w/ myosin (motor molecule)
How actin filaments grow?
+ end has a higher affinity for rapid polymerization(5-10x faster), - end has lower affinity.
- the Kd on each end is sufficiently different where you can have + end polymerizing and - end depolymerizing
- Kd of molecule > than +/ end Kd then the molecule will polymerize to that specific end
POLYMERIZATION REQUIRES ATP..actin needs ATP to grow
The two forms of actin?
- pre-polymerization= G- actin (globular actin); are monomers
- once polymerized and become filament= F-actin (filamentous)
What is tread milling?
- reversible polymerization of actin monomers
- occurs when a G-actin has a Kd> than + end; but lower than - end; so polymerizes to + end then falls off - end “tread milling”
- important for us to change shape of cell and motility of cell
AtP hydrolysis and actin?
-remodeling of actin filaments is responsible for half of of ATP hydrolysis in cells
How does actin work to maintain cell shape and as an anchor?
- actin networks bind to cytoskeleton proteins among other structures below the plasma membrane & together they determine cell shape
- anchor: actin crosslinks to PM to anchor cell-cell & cell-substratum contacts
- cross links these elements so bound to transmembrane domain proteins
The mechanical properties of the cytoplasm?
- regulated b y cross linking of actin
SLOW pressure gives actin time to react & adjust
RAPID deformations does not so are resisted
-if stretching is too strong & happens too fast, will break actin
How does actin filament turnover/ monomer recycling occur?
-regulated by accessory proteins (caps for ex)
1) can cap + or 1 end, to regulate polymerization/depolymerization
2) can cap & sever long filament–> shorter filament
3) PROTEINS can sever long filament w/o cap
4) PROTEINS can help crosslink/bund actin
How make bundles/networks of actin?
-by using actin-binding proteins to crosslink the actin filaments
How extrinsic signal regulating actin cytoskeleton?
1) PIP2 binds prolifin, prevents it from interacting w/ actin
2) PLC makes PIP2 –> IP3–> releases actin, promote filament growth
3) Gelsolin and coffin: actin severing proteins, increase number of + ends to increase actin growth, inhibited by PIP2
Gelsolin and coffin
actin severing proteins, increase number of + ends to increase actin growth, inhibited by PIP2
PIP2 name?
-phosphinositol bis phosphate
how does GPCR/G-proteins that control cell shape & behavior?
- Rho G protein family has Rac, Rho & Cdc42 pathways
1) Cdc42 activates rapid actin polymerization
Cdc42 pathway
Cdc42 activates rapid actin polymerization & bundling, causing cell to put out filopodia
Rac pathway?
uncaps + end of filament, stimulates filament elongation, causes cells to form lamellipodia & membrane ruffles
Rho pathway?
- stimulates filament bundling, causing cells to form stress fibers that interact with focal contact points with the extracellular matrix
Diseases associated with actin filaments due to? (2)
1) mutations in actin
2) mutations in actin modifying/signaling molecules
-typically mutations in actin itself are too sever and result in death; so more common to see mutations in actin accessory proteins
How many actin genes are there?
-6 actin genes (2 non-muscle)
-
TAAD (thoracic aortic aneurysms and dissections?
22 missense mutations in alpha smooth muscle actin lead to this
Autosomal dominant non syndromic hearing loss
12 known missense mutations in gamma non muscle actin cause this
Duchenne’s & beckers muscular dystrophy?
- due to mutations in dystrophin
- dystrophin links actin filaments to transmembrane proteins of muscle cell PM
Pathogens utilization of actin?
- pathogens can hijack actin network to get their biology dominant over ours
1) Listeria come in through endosome vesicles, vesicles degrade
2) get accumulation of actin around listeria DNA
3) Listeria organize actin, nucleate it specially on one end (TAILS), and use it to shoot like rocket to infect next cell OR move around the cell to acquire whatever it needs
What is directed cell migration of chemotaxis important for?
- chemotaxis= movement toward something*
1) developmental patterning (make sure limbs/ organs go to right place)
2) immune cell function
3) wound healing
4) tumor cell metastasis
What is hyperactive cell migration? What related to?
- is not good, don’t want this to happen
- related to chronic inflammation & metastatic cancer
What is defective cell migration related to?
- immune suppression
- poor wound healing since won’t be able to have tissue repair since fibroblasts can’t get together since cell is moving too fast
types of signaling cascadeds (2) and cell migration regulation?
1) small GTPases of Rho family
2) Kinases like MAPKs
- typically downstream of GPCRs
- signaling cascades= independent of gene expression/translation
How can signaling molecules alter membrane structure?
- signaling proteins can target assembly of actin microfilaments & association of actin with linking proteins to alter membrane structure
What does a cell need to do to migrate?
POALRIZE TOWARD A SIGNAL 1) disassemble some filaments 2) form new filaments 3 form branched filaments (lamellipodia) 4) continue to sense the signal through fillopdia formation 5) reattach at new site
lamellipodia
- cytoskeletal protein actin projection on leading edge of the cell
- propels a cell
fillopdia
- slender cytoplasmic actin projections that extend beyond the leading edge of lamellipodia in migrating cells
- made from actin networks/bundles
How do we form a leading edge?
–actin filaments polymerize to free barbed end, branch and push membrane out
How do we get branching? which requires polymerization from the SIDE of a filament.
1) chop up exiting filaments w/ COFILIN
2) protein complex ARP2/3 works w/ WASP signaling proteins to help w/ branching
COFILIN
1) create actin seeds for elongation by chopping up actin into smaller pieces
2) reorganizes exist filament structure
3) allows for tread milling of filaments at leading edge
ARP2/3 + WASP mechanism?
- binds to acid and serves as seed for polymerization
- Arp2/3 can’t get correct conformation w/0 being activated by WASP family proteins
Wiskott-Aldrich Syndrome
- disease of cytoskeleton (no branching of actin, no lamellipodia)
- bleed easily; low platelet count
- recurrent infections; deficiency of T & B cell function
- eczema
- cause necrotizing vasculitis if not treated
-DUE TO DEFECTS IN WASP PROTEINS
