[W7] Cell adhesion and migration

Question 1

Why is cell migration important in biology?

Answer 1

It plays a role in cancer metastasis, angiogenesis, wound healing, pregnancy, embryonic development, and immune responses.

Question 2

What are the four main steps in the cell migration process?

Answer 2

1. Protrusion of the leading edge
2. Adhesion to the surface
3. Traction (cell pulls itself forward)
4. Retraction of the rear

Question 3

What is the role of actin in cell migration?

Answer 3

Actin filaments create protrusions at the front of the cell (lamellipodia), determine cell shape, and enable movement.

Question 4

What is a lamellipodium?

Answer 4

A broad, actin-rich protrusion at the front of a migrating cell formed by actin branching and polymerisation.

Question 5

How do actin filaments grow during migration?

Answer 5

Actin monomers bound to ATP add to the plus end of the filament.

Question 6

What is the extracellular matrix (ECM)?

Answer 6

A network of proteins like collagen, proteoglycans, and fibronectin that provides structural and biochemical support to cells.

Question 7

What are integrins?

Answer 7

Cell surface receptors that connect the ECM to the actin cytoskeleton and transmit signals into the cell.

Question 8

How do integrins switch from inactive to active?

Answer 8

They change shape upon binding ECM ligands, allowing attachment of intracellular adaptor proteins.

Question 9

What are adhesion complexes (focal adhesions)?

Answer 9

Protein complexes that link integrins to the actin cytoskeleton, providing stable attachment to the ECM.

Question 10

What is talin?

Answer 10

A cytoskeletal adaptor protein that links activated integrins to actin filaments.

Question 11

How do adhesion complexes differ in migrating vs. stationary cells?

Answer 11

In migrating cells, they are small and dynamic; in stationary cells, they are large and stable.

Question 12

What are the three types of motor proteins involved in intracellular transport?

Answer 12

Myosin (actin-based), kinesin, and dynein (both microtubule-based).

Question 13

What is the role of myosin in cell migration?

Answer 13

It pulls the cell body forward by walking along actin filaments attached to adhesion complexes.

Question 14

What powers myosin movement?

Answer 14

ATP hydrolysis.

Question 15

What is chemotaxis?

Answer 15

Directed cell movement in response to a chemical gradient (e.g., chemokines or nutrients).

Question 16

What molecules guide chemotaxis in multicellular organisms?

Answer 16

Chemokines, which are secreted during infection, injury, or stress.

Question 17

What are Rho GTPases?

Answer 17

A family of small GTP-binding proteins that regulate cytoskeletal dynamics and migration direction.

Question 18

Name the three key Rho GTPases involved in migration.

Answer 18

Rho, Rac, and Cdc42.

Question 19

What does Rac do in cell migration?

Answer 19

Promotes actin branching and lamellipodia formation.

Question 20

What does Rho do in cell migration?

Answer 20

Promotes formation of stress fibres and cell contractility.

Question 21

What does Cdc42 do in cell migration?

Answer 21

Controls cell polarity and direction changes during turning.

Question 22

How are Rho GTPases activated?

Answer 22

By GEFs (guanine exchange factors), which swap GDP for GTP.

Question 23

How are Rho GTPases inactivated?

Answer 23

By GAPs (GTPase-activating proteins), which promote GTP hydrolysis.

Question 24

What is the role of GDIs (GDP dissociation inhibitors)?

Answer 24

They keep Rho GTPases in the inactive GDP-bound state in the cytosol.

Question 25

What is epithelial–mesenchymal transition (EMT)?

Answer 25

A process where epithelial cells lose adhesion and gain migratory properties—crucial in metastasis.

Question 26

What are MMPs?

Answer 26

Matrix metalloproteinases—enzymes that degrade the ECM, facilitating cancer cell invasion.

Question 27

How are MMPs regulated?

Answer 27

They are secreted as inactive proenzymes and activated extracellularly.

Question 28

What are TIMPs?

Answer 28

Tissue inhibitors of metalloproteinases—natural inhibitors of MMPs that are often downregulated in cancer.

Question 29

How do tumour-associated fibroblasts aid migration?

Answer 29

They remodel the ECM and secrete factors that help tumour cells move.

Question 30

How do cancer cells enter the bloodstream?

Answer 30

By crossing the endothelium, often by causing endothelial cell retraction.

Question 31

What role does the lymphatic system play in metastasis?

Answer 31

It provides an early route for tumour cells to spread to lymph nodes and later into circulation.

Question 32

What is the TNM system of cancer staging?

Answer 32

T = tumour size, N = lymph node involvement, M = distant metastasis.

Question 33

How does metastasis affect survival?

Answer 33

The more widespread the metastasis, the poorer the prognosis.

Question 34

Summary – how do cells migrate?

Answer 34

By using actin-based protrusion, integrin-mediated adhesion, myosin-driven traction, and chemotaxis signals.

Question 35

Summary – how do cancer cells spread?

Answer 35

They undergo EMT, degrade ECM using MMPs, evade inhibitors (like TIMPs), and enter the bloodstream or lymphatics.