Cytoskeleton 2 - Dr White Flashcards
Slides to be familiar with
Slides to be familiar with
How does listeria and ARP complex work together
Listeria usese surface protein called actA to activates Arp 2/3 complex and cause local nucleation of actin filaments which are cross linked
addition of actin branched filaments pushes the bacteria along and force pushes
(cofilin dissassembles branced actin)
What is cofilin?
Binds to ADP actin filaments annd accelerates disassembly
“actin depolymerization factor”
binds to oth actin filaments and free actin subinits
binding of cofilin forces the filaments to twist a little mre tightly and weakens the contacts b/w actin subunits making filaments more brittle and more easily cut
removes actin tail in listeria
What is gelsolin
severs actin filaments and binds to plus end
makes smaller filaments availble for elongation or disassembly
helps with new and rapid assembly or disassembly deponds on conditions sometimes polymerization and other depolymerization
What are the microtuble accessory proteins ?
- Tublin Dimers
- microtubles
- filaments cross linking
What is lysteria?
RANDOM iNFO
- symptons are : heaches, stiff necks, confusion, loss of balance , convulsions, fevers, and muscle aches
- causes food pausing if your immunologically deficient or immunocompromised
- 10x more likly if pregnant
- 1/5 ppl die
- 20% fetal loss and 3% newborn death of cases
TEST INFO BELOW
- PAthogenic bacteria that invades your intestinal cells
- treated with IV antibiotics
- Listeria attaches to receptors one enterocytes
- enters and replicates in your intestinal cells
- unusual behavior based on actin cytoskeleton and acessory proteins
What are the accessory proteins related to filament bundling, cross linking and attachemnt?
A actinin
fimbrin
filamin
spectrin
ERM family
What are the accessory proteins that affect actin subunits
ARP COMPLEX **** - ACtin related protein -> (listeria)
Formin
THymosin:
Profilin:
What is kinesin
Protein that uses an ATP to walk along a microtuble track to move vesicles
walk towards plus end of microtuble
carry a binding site in the tail for a membrane enclosed organekke
What is thymosin?
Thymosin: binds actin sub units, prevents assembly
regulations of availability of actin monomers for actin. keeps actin monomers soluble so they are readily avaible for generating filaments
actin monomers - thymosin are in locked state
what are the microtuble accessory proteins
Katanin : severs microtubles
MAPS: “microtuble associated protein)
- stablizes tubles by binding along sides of microtubles
- stabilize microtubles against dissembly *
- inhibts switch from growing state to sjrinking state “catastrophe supressed and growth enhanced”
XMAP215
- a microtuble associated protein that stabilizes plus ends and accelerates assembly
- stabilizes free ends of microtuble and inhibits the switch from the growing to shrinking state
- catastrophes supressed and growing enhanced
Kinesin 13
- : enhances catastrophic disassembly at plus end
- by lowering activation energy barrer that prevents microtuble from springing apart
What are dynein arms ?
MIcrotubule motors
- MInus end directed mictotuble motor
- largest of known moleuclar motors and the fastest
Cytoplasmic dyneins
- vescicle trafficking, localization of golgi apparatus
Axonemal dynein
- Specialized for rapid and efficient sliding movements of microtubles that drive the beating of cilia and flagella
What is profilin?
recruits actin monomers to actin filament for polymerization
- profilin binds to an actin monomer
- exposes sit of actin that binds to pplus end of actin filament
- addition of an actin monor induces confernation change in actin reduces affinity for profilin
- profilin faills off leaving actin filament on subunit longer
What is formin?
Formin - Nucleates the assembly of long, unbranced chains + remains associated witht the growing plus end
along with arp help catalzye and determine shape and movement of the cell surface
dimeric protieins that can jnucleate the formation of a new actin filament
causes growth of STRAIGHT AND UNBRANCED actin filaments
What is spectrin?
Atttaches cytoskeleton to membrane
Confers property of durbility and stability to RBCs
defective results in disease called hereditary spherocytosis (HS) fragile red blood cells and anemia
Slides to be familiar with
What does tropomodulin do?
Prevents assembly and disassembly at minus end - stabilizes actin filaments - for long lived filament stabilization
Stablization
prevents assembly and disassembly at minus end
stabilizes actin filaments
What is alpha actinin
CRoss links actin filaments into loose bundles, allowing myosin 2 to enter to make actin filaments contractile
alpha actinin and fimibrin tend to exclude one another because of different functions
What is filamin
promatoes the formation of loose, highly viscous gel like networks by clamping together 2 actin filaments
cells require the actin gel in order to extend membrane projets
HELPS CELL CRAWL ACROSS SOLID SURFACE
cannot crawl without filamin
What is ERM family?
The ERM (ezrin, radixin, moesin) attaches to cytoskeleton to membrane
mediates the attachemnts between actin and plasma membrane
two binding sites: one to bind to actin filament and one to bind to transmembrane protein
What are the three types of actin filament acessory proteins?
- affect actin subunits
- affects actin filaments
- affects filament bundling, cross linking, and attachment to membranes
What is tropomyosin?
Stabilizes filaments - prevens binding with other proteins.
What is fimbrin?
Cross links actin flaments into tight bundles exulding myosin 2
what is chemotaxis and list one example of it?
A cell movement in directon controlled by a gradient of diffusible chemical
Neutrophils toward a source of bacterial infection by detecting peptides that are dervied from bacteria proteins
What are two groups of cytoskeletal motor proteins? and how do they work?
Dyneins arms and kinesin
- Bind to polarized cytoskeletal fialments
- use eneregy dervived from ATP hydrolysis tp move steadily along filament
- carry memrane enclosed organelles to appropriate locations
- Cause sytoskeletal filaments to exert tension
- slide against each other generating force that drives muscle contraction or cell division
- associated with their filament tracks through head region
- motor domain
- Head (determines identy of track and direction of movement)
- tail determines identity of the cargo repersents biological function of motor protein
- hydrolzies ATP
What are the accessory proteins that affects actin filaments ?
- Stablilizing
- Tropomodudlin
- tropomyosin
- capping proteins
- Disassembly
- Cofilin
- gelsolin
*
What are the filament cross linking binding proteins?
Plectin: cross linking protien links microtubles to intermediate filaments
Tau: a map protein MAP2 both cause bunding of microtubles
MAP2 has a long projecting domain
- forms bundles of stable microtubles that are kept widely spaced
TAU binds to microuble at both termini
- shorting and forms bundles that are more closely packed mictotubles
What is ARP complex?
ARP COMPLEX **** - ACtin related protein - nucleates assembly to form weblike, HIGHLY BRANCHED chains and remains assocated with minus end (listeria)
ARP2 and ARP3 are 45% identical to actin
growth from minus end allowing for elongation at the plus end
requires activating factor
Works most efficiently when bound to sinde of pre exhisting actin filaments (cross link) at a 70 degree angle
What are reuqies of cell crawling and why does this matter?
- Cells must produce polarity (front vs rear)
- Cells must move fowards but also must drage rear (retraction of rear of cell)
- Important role in many cancers.
- Cells invaved nieghboring tissues using this (metastases)
- Crawl into blood or lymph vessels
What are the tublin dimers
Strathming: binds suninots, prevents assembly
TIPS: the plus end tracking proteins growing plus ends and can link them to sttructures such as membranes
gamma - TuRc **** = nucleates the assmebly and remains assocaties witht the minus end
- resonsible for mucleation fo microtuble growth
- attached to centrosome at the minus end of the microtubles
- serves as a template that creates a microtubles with 13 protofilaments
what is a capping protein?
prevents assembly and siassembly at plus end .
binds to plus end and stabilizes actin filament
reduces rate of polymerization and depolymerization
