Exam 4 (8)

Question 1

Role of Integrins in Cells

Answer 1

Interact with multiple ligands to play key roles in signaling, morphogenesis, and movement; links the actin filaments and ECM using Actin Binding Proteins (Talin and Vinculin)

Also a part of the connection between stress fibers and focal adhesions

Question 2

2 Conformations of Integrins

Answer 2

Extracellular and Intracellular Sides are either low affinity/inactive OR high affinity/active

Question 3

Signaling Role of Integrins

Answer 3

Mediates inside-out (cytoskeletal to ECM) and outside-in (extracellular matrix then alters cytoskeleton)

Question 4

Mediating Talin binding and Integrins

Answer 4

RTKs or G-coupled Protein Receptors can phosphorylate talin and activate integrins

Question 5

Outside-In Signaling Pathway (4 Steps + 3 Example Responses)

Answer 5

Integrins engaged by ECM protein –> signal to non-receptor tyrosine kinases (focal adhesion kinase + c-Src) –> activates PI3K + Rho-family GTPase –> diverse responses (proliferation, actin rearrangements, transcription)

Question 6

After the protrusion caused by the lamellipodium during cell movement, what causes the cell to adhere to the surface it is trying to move forward on?

Answer 6

Focal Adhesions

Question 7

4 Steps in the Mechanism of Cell Movement

Answer 7

1) Protrusion of Lamellipodium: forward force from actin polymerization
2) Adhesion: lamellipodium interacts with surface/substrate to form focal contacts/adhesions
3) Cell Body Translocation: myosin-mediated contraction (stress fibers) of actin pulls the cell forward
4) Deadhesion/Tail Retraction: rear of cell deanchors + moves forward