MCB 3rd Unit 1 Flashcards
Filament that supports cell shape and structure as well as forming a band to separate dividing cells
Actin
Free actin monomers are referred to as:
Globular actin or G-actin
F actin is:
Actin monomers creating a double helix = microfilaments or thin filaments (myofibrils)
Thick filaments are made from:
Myosin motor proteins
Thin filaments are associated with:
Myofibrils (muscle)
Which end of the actin filament is slow growing?
- end
Which part of the actin filament is fast growing?
+ end (bind monomers with affinity due to ATP)
The change from ATP to ADP is what type of chemical process?
Hydrolysis
Adding ATP bound G-actin monomers to the + end of the filament whilst ADP bound monomers are removed at the - end, resulting in a filament that maintains the same length is a process called:
Treadmilling
Shrinkage and growth (catastrophe and rescue) termed “dynamic instability” was a characteristic of:
Microtubules
True or false, affinity of actin monomers follows this progression:
Filament>nucleus>each other
True
What protein exchanges ADP for ATP, readying the monomer for attachment?
Profilin
What protein stimulates nucleation of G-actin into dimers/trimers
Arp 2/3
What protein initiates polymerization if actin?
Arp 2/3
The ARP complex nucleates filaments more effectively when bound where?
What does this create?
To the side of preexisting actin filaments, a branched/webbed actin network
What protein nucleates the growth of straight, unbranched actin filaments which become crosslinked by other proteins forming parallel bundles?
Formins
Which protein binds G-actin and prevents F-actin assembly?
Thymosin
What protein binds G-actin and promotes filament assembly at the + end? (Actin ADP->ATP)
Profilin
What protein caps the + end of the actin filament to prevent further growth?
Gelsolin
What protein severes and depolymerizes ADP actin filaments?
Cofilin
Which type pf myosin is involved with contractile activity (both muscle and non-muscle)
Myosin II
Which type of myosin is involved in protrusion of actin-rich structures like microvilli?
Myosin I
Which type of myosin is involved in vesicle and organelle transport?
Myosin V
Name 3 actin cross-linking proteins which form parallel cables/bundles
Alpha-actinin, fimbrin, and villin
Name 2 actin cross-linking proteins which form filament webs/gels
Spectrin and filamin
Actin bundles and web-like organizations are initiated by ___ and stabilized by ____.
Nucleating proteins, cross-linking proteins
Name four non-muscle functions of actin
Microvilli
Stress fibers
Cell surface protrusions (cell migration)
Cytokinesis
Alpha-actinin is loosely packed and contractile, used for:
Stress fibers
Fimbrin is tightly packed and non-contractile, used for:
microvilli
How do actin stress fibers within the cell bind to ECM to allow movement?
Use integrin receptors at “focal adhesion” sites
What proteins at the cell surface activate nucleating proteins (arp 2/3 complex and formins)?
Rho GTPases
RhoGTPases located at the cell surface activate:
nucleating proteins
Which RhoGTPase is responsible for formation of lamellipodia?
rac
Which RhoGTPase is responsible for formation of filipodia?
cdc42
Which RhoGTPase is responsible for formation of stress fibers?
rho
A severe X-linked immunodeficiency syndrome involving a mutation in WASP protein resulting in an inability to activate Arp2/3 and thus failure of actin nucleation
Wiskott-Aldrich Syndrome
Name 3 drugs t hat can bind to actin filaments
Cytochalasins, plahhoidin, latrunculin
Thick filaments of myofibrils are made up of:
Hundreds of myosin II motor proteins
Thin filaments of myofibrils are made up of:
Actin filament with tropomyosin and tryponin complex
What protein links the actin cytoskeleton with the integral membrane glycoprotein complex that interacts with the ECM?
Dystrophin
Dystrophin links the actin cytoskeleton to which protein specifically?
Laminin-2
Muscle is repaired by which cell populations? Which does more?
Satellite cells and side population cells, satellite cells
What is a bloodwork flag for muscular damage?
Increased serum creatine kinase
What is the most severe type of muscular dystrophy and what is it’s inheritance pattern?
Duchenne MD, X-linked
Which type of LGMD is AR?
LGMD 2
Congenital muscular dystrophy involves a mutation in what protein?
Laminin
What is an adhesive glycoprotein that anchors epithelial cells to the basal lamina via integrin receptors?
Laminin
What type of collagen binds with laminin to form scaffold for basal lamina?
Collagen type IV, “sheet forming” collagen
What two ECM proteins bind laminin and collagen IV, connecting the two networks?
Entactin and perlecan
GAG’s carry what charge? How does this attract water?
Negative charge attracts cations which attract water
In hyperglycemia, downregulation of ____ causes collagen glycosylation and cross-linking causing thickening of the GBM
HSPG
Integrin receptors bind to the ____ sequence of fibronectin/laminin
RGD
What type of fibronectin is made by the liver and circulates in the blood enhancing clotting?
Soluble plasma fibronectin
What type of fibronectin is formed on the cell surface and deposited in the ECM?
Insoluble fibronectin fibrils
Integrins bind laminin in the _____ and fibronectin in the ____.
Basal lamina, connective tissue
In _____, integrins bind keratin intermediate filaments in the cell cia adaptor proteins (plectin) and to laminin in the basal lamina
Hemidesmosomes
In _______ adhesions, integrins bind to actin stress fibers via adaptor proteins (vinculin and talin), and to fibronectin in the connective tissue
Focal adhesions
______ cross links actin stress fibers
Alpha-actinin