Lecture 29 Flashcards
Which type of focal adhesion junctions tends to be immobile
Low density adhesions
Glanzmann’s thrombasthenia is a disease associated with integrins. Discuss the cause and symptoms of this condition
Glanzmann’s thrombasthenia is caused by a mutation in integrin ?IIb?3 that causes symptoms similar to haemophilia. The abnormal integrin impairs platelet function and causes easy bruising and increased likelihood of bruising
What part of the actin cytoskeleton involved in cell motility is responsible for membrane tension and the transmission of tension
Actin cortex
Focal adhesions act during necrosis, T or F
F – the act during anoikis or attachment-dependent cell death
Outline the process of traditional cell migration
The actin-polymerisation-dependant protrusion and the firm attachment of lamellipodium at the leading edge of the cells moves the edge forwards and stretches the actin cortex. Contraction at the rear end of the cell propels the body of the cell forwards to release some of the tension. Finally, new focal adhesions are made at the front and the old ones are disassembled at the back as the cell crawls forwards
Which type of focal adhesion junctions are Rac1 and cdc42 dependant
Low density adhesions
What is the role of focal adhesion kinase (FAK) in cell adhesion and integrins
FAK is a cytoplasmic protein tyrosine kinase present at cell-matrix junctions in association with the cytoplasmic tails of integrins. It is activated on formation of adhesions but may actually inhibit focal adhesions. FAK is also regulated by the concentration of intracellular Ca2+
What three proteins are involved in the maturation of focal adhesions
Actin-binding proteins (ABPs), small G-proteins and myosin
What is the name of the complex responsible for nucleation of the actin filament and what is the involvement of Rac
Arp2/3 – stimulated by Rac activity
Which termini make up the intracellular and extracellular domains of integrins
The C-terminus forms the intracellular regions of the proteins whilst the N-termini are found in the extracellular domain of the receptors
What is the role of endocytosis in cell motility
Endocytosis of a secreted factor alternates the concentration of that factor. In addition, when integrins and other CAMs bind to ligands and extracellular matrix proteins they can be taken into the cell which alters the way the cell subsequently interacts with the extracellular matrix
How many different known varieties of integrins are there
24 known integrins (from 18? subunits and 8? subunits)
Fibronectin is an extracellular matrix protein that binds to integrins, what sequence is responsible for this binding
RGD – arginine-glycine-aspartate
Focal adhesions act through integrins, T or F
T
Which proteins and interactions are required for formation of the high density adhesions
RhoA and actin-myosin interactions
Explain the role of membrane cycling in cell motility
Membrane endocytosis is occurring constantly around the whole cell. Meanwhile, exocytosis occurs at leading edge leading to an addition of phospholipid bilayer and an increase in the surface area of the membrane. This corresponds to a net membrane addition which could provide a net motive force for cell motility. There is also a net rearwards flow of membrane as membrane is constantly added at leading edge which shifts existing membrane backwards. Therefore, if the membrane is fixed by focal contacts the cell will move forward
What is meant by a focal adhesion
Focal adhesions are areas of temporary attachment of a cell to the medium it is moving through
What is the proposed difference in timing of the two types of focal adhesions during their maturation
Low density adhesions that are immobile tend to appear earlier, whereas, high density adhesions appear later and are motile
Binding of which cations effect the binding of the two integrin glycoproteins
Ca2+ and Mg2+
What is the role of fibronectin in migration of the neural crest cells
Fibronectin trails allows neural crest cell migration.
To which cytoskeletal element do the majority of integrins bind link to
Actin filaments
Signals to dictate cell motility can be soluble or insoluble, give examples of both
Soluble – netrins, insoluble – CAMs
Mammalian cell motility is interlinked with adhesion and is mostly actin-based, T or F
T
What are the two types of focal adhesion junctions
Low density adhesions and high density adhesions
What is the name of the specific motif that integrins bind to on target extracellular matrix proteins
RGD – arginine-glycine-aspartate
Integrins are a key class of cell adhesion molecules. Explain the role integrins
Integrins are extracellular matrix receptors present in the membrane of cells. They act to link the extracellular matrix to the cytoskeleton
Describe the structure of integrins
Integrins consist of two, non-covalently associated glycoproteins each with an ? and ? subunit.
