invasion- regulation of cell migration

Question 1

DIAGRAM summary of tumour progression

Answer 1

normally there is homeostasis, but genetic mutations cause hyper-proliferation, causing the cells to DE-DIFFERENTIATE: they lose polarity and cell-cell contact invasion then occurs, where cells move more, ECM proteins are broken down, so cells invade basement membrane invasion is where benign becomes malignant

Question 2

what occurs in metastasis

Answer 2

normally, BM separates epithelial cells from stroma- but these cells invade the MB and enter blood, travel to new location, and invade another organ

Question 3

types of tumour cell migration- examples of individual and collective with types of cancer

Answer 3

can either migrate individually or collectively individually are ameoboids (occurs in lymphoma/leukemia) or single mesenchymal cells (occurs in glioblastoma) collectively are clusters (occurs in epithelial cancer/melanoma) and multicellular strand (epithelial cancer/vascular tumours)

Question 4

what molecules are more present in collective vs individual

Answer 4

integrins and proteases are present more in collective tumour cell migration (in clusters, more ECM proteins broken down= more invasion) also more cadherins and gap junctions (cells in clusters need to communicate with each other)

Question 5

how to analyse migration of primary glial cells vs tumour cells

Answer 5

scratch wound assay- in the middle of glial cells, put a scratch- normal glial cells sense space and migrate there together, and then stop once no more space left tumour cells migrate much more faster and randomly- no organisation, and they KEEP growing

Question 6

what occurs when growth factor given to invasive cells

Answer 6

invasive cells migrate to the growth factor, thus there’s an upregulation of genes involved in motility and cytoskeleton

Question 7

stimuli causing cell movement

Answer 7

wounding, growth factors, dedifferentiation ie tumours, and organogenesis

Question 8

DIAGRAM how cells know where to move, how they move and how they stop

Answer 8

cells change shape and become polarised, with a front and a back: they move using special strucutres they stop by contact-inhibition motility

Question 9

DIAGRAM how cells begin movement ie attach to substratum

Answer 9

there are integrins which are activated- a plaque of proteins then form which include FOCAL ADHESIONS- they then attach to substratum (proteins in ECM) via FILAMENTOUS ACTIN (ie cytoskeleton)

Question 10

how cells become MOTILE

Answer 10

FILOPODIA- FINGER-like protrusion rich in actin and VINCULIN: they sense the surrounding environment LAMELLIPODIA- SHEET LIKE protrusion rich in acti

Question 11

types of motility

Answer 11

hapoptatic- no purpose, movement is random without a sense of direction chemotactic- sense of direction, more of a purpose

Question 12

DIAGRAM summary of cell motility

Answer 12

cells have focal adhesion which acts like feet- they attach to BM cell then extends via lamellipodium (like a hand reaching out) cells then form a new focal adhesion cells then move via muscle contraction previous adhesion is removed

Question 13

DIAGRAM actin filaments types- what occurs upon signal

Answer 13

when there is a signal eg nutrient source, F actin (large polymer) break down into G actin (small subunits) so that they can move, and F actin reassembles at new site so that cell can migrate to new site

Question 14

DIAGRAM actin filament organisation in different structures

Answer 14

lamellipodium has short branched cross linked filaments filopodium has parallel filaments stress fibres are ANTIPARALLEL to allow cell contractio

Question 15

remodelling of actin filaments

Answer 15

G actin/F actin can become different arrangements of proteins for different purposes

Question 16

1st stage of polymerisation- nucleation

Answer 16

actin undergoes nucleation with ARP proteins to initiate polymerisation: this is the LIMITING STEP

Question 17

2nd stage- elongation

Answer 17

once small actin filament formed, PROFILIN helps elongate it, which competes with THYMOSIN, which inhibits elongation

Question 18

3rd stage- capping with examples

Answer 18

capping proteins either go onto negative or positive end of actin filament, telling it to stop growing CAPZ/tropomodulin and ARP complex (also does capping as well as nucleation)

Question 19

4th stage- severing with complex

Answer 19

actin filaments are cut into smaller parts by severing proteins eg gelsolin ie depolymerised

Question 20

what occurs to severed protein

Answer 20

either capped, two severed proteins are reannealed, or further growth occurs

Question 21

next stage- cross linking/bundling with examples

Answer 21

multiple filaments are connected together by proteins to stabilise them eg fascin, fimbrin, alpha actinin, spectrin, dystrophin

Question 22

next stage- branching

Answer 22

ARP complex AGAIN is a branching protein- a branch of an actin filament forms at a 70 degree angle

Question 23

next stage- gel-sol transition by actin filament severing

Answer 23

due to cross linking, a GEL is formed which is rigid when filaments need to go through basement membrane/move, severing occurs to form a SOL, which is not rigid and can flow

Question 24

DIAGRAM different actin activities during cell migration

Answer 24

polymerisation when lamellipodium is extending- involves all stages including disassembly at start (F to G actin), then gel/sol transition actin then ATTACHES to ECM actin then CONTRACTS actin then DETACHES

Question 25

DIAGRAM lamellae protrustion

Answer 25

disassembly BEHIND leading edge polymerisation, BRANCHING and capping then occurs assembly occurs at LEADING edge

Question 26

filopodia

Answer 26

finger like protrusions- polymerisation occurs, cross-linking/bundling then occurs, and capping proteins form at top to prevent further growth

Question 27

different molecules with different types of organisation of actin

Answer 27

bristle, microvilli have long finger like action stereocilia have actin of increasing order filopodia lamellopodia has actin arranged randomly and in BRANCHES

Question 28

different mechanisms regulating actin cytoskeleton

Answer 28

ion flux changes ie Ca2+ phospholipid binding kinases signalling cascade via small GTPases

Question 29

DIAGRAM- control via G proteins, example, and what occurs in tumours

Answer 29

eg Rho, belongs to Ras family Rho has a GDP, which becomes GTP using hydrolysis of ANOTHER GDP elevated in tumours

Question 30

DIAGRAM main G proteins, and what they produce

Answer 30

RhoGTP produces stress fibres RacGTP produces lamellipodia Cdc42GTP produces filopodia thus they all control actin polymerisation

Question 31

DIAGRAM effect of small GTPase on cell migration

Answer 31

Rac involved in extension by actin polymerisation Rac and Rho involved in forming new adhesion, Rho mainly needed for contraction and deadhesion Cdc42 not involved in migration directly, but needed for sensing WHERE to migrate