L30 - Angiogenesis, VEGFR and Hypoxia (2)

Question 1

how many isoforms of VEGF are there

Answer 1

5 A-D + PlGF (Placental Growth Factor)

Question 2

Structure of VEGF

Answer 2

glycoprotein (40-45kDa)

exist in dimer in an anti-parallel, side-by-side orientation

Question 3

how many VEGFR are there

Answer 3

3 major types- VEGFR1-3 also called Flt-1, Flk-1, Flt-4

Question 4

what VEGFR binds which VEGF-ligand

Answer 4

VEGFR-1/Flt-1 = A, B, PGIF
VEGFR2/KDR/Flk-1= A, C, D
VEGFR-3/Flt-4 = C, D

Question 5

what are the roles of each VEGFA

Answer 5

• VEGF-A: Stimulates angiogenesis and vascular permeability

Question 6

what are the roles of each VEGFB

Answer 6

• VEGF-B: Involved in cardiac muscle survival and lipid metabolism

Question 7

what are the roles of each VEGFC

Answer 7

• VEGF-C: Regulates formation of lymphatic vessels

Question 8

what are the roles of each VEGFD

Answer 8

• VEGF-D: Promotes lymphatic vessel growth

Question 9

what are the roles of each PIGF

Answer 9

• PlGF (Placental Growth Factor): Supports angiogenesis during pregnancy

Question 10

Expression of VEGFR

Answer 10

Endothelial cells, Monocytes, lymphatis endothelial cells

Question 11

VEGFR structure

Answer 11

ECD: 7 immunoglobulin structures
ICD: kinase domain

Question 12

VEGFR1 receptor activation

Answer 12

phosphorylation largely Y1213, lesser extent Y1242 and Y1333

Question 13

VEGFR1-VEGFA binding

Answer 13

high affinity but weak tyrosine kinase activity

Question 14

VEGFR1-VEGFB binding

Answer 14

no downstream signalling →
displace VEGFA→ ↑VEGFR2 activity

Question 15

VEGFR1-PIGF binding

Answer 15

Y1309 phosphorylation site

Question 16

VEGFR2-VEGFA receptor activation

Answer 16

p-Y951 → Src kinase → cytoskeleton organization and migration

p-Y1175→ eNOS activation →
proliferation and migration

P-Y1214 → p38 MAPK → actin
remodeling and cell migration

Question 17

VEGFR3-VEGFC/D receptor activation

Answer 17

largely Y1337-> PLC/PK mediated p42/44 signalling and PI3K signalling pathway

Question 18

what is neruophilins

Answer 18

Co-receptor of VEGFR
- enhance ligand binding
- signal amplification
- control ligand receptor signalling

Question 19

how do neurophilins enhance ligand binding with exmaples

Answer 19

bind directly to specific VEGF isoforms
e.g. NRP-1: Binds VEGF-A165, VEGF-B, and PlGF
NRP-2: Binds VEGF-C and VEGF-D

Question 20

how do neurophilins enhance signal amplification

Answer 20

form complexes with VEGFRs → Strengthen VEGF ligand binding and stabilize the VEGF-VEGFR complex

Question 21

how do neurophilins control ligand-receptor selectivity with examples

Answer 21

Ensuring the proper VEGF isoform interacts with the correct VEGFR
e.g. NRP-1 + VEGFR-2: Promotes angiogenesis and vascular perm.

NRP-2 + VEGFR-3: Facilitates lymphangiogenesis

Question 22

VEGF Receptor 1 : Signal transduction

Answer 22

PI3K ->PIP3->Akt/PKB-> eNOS-> pro NO -> Ca+ -> migration

PLC-y-> DAG +IP3 -> Ras -> Raf -> Mek-> erk -> proliferation

Question 23

Regulation of VEGF using HIF

Answer 23

Hypoxia (↓ O2 level) → ↓prolyl hydroxylas (PHD) → HIF-1α stabilization → binds to hypoxia response elements (HREs) in the VEGF gene promoter → ↑VEGF transcription → ↑ angiogenesis

Question 24

conditions associated with too much angiogenesis

Answer 24

cancer, diabetic retinotherapy, rheumatoid arthritis, AIDS comx, psoriasis

Question 25

conditions associated with insufficient angiogenesis

Answer 25

chronic wounds, coronary heart disease, hypoxia, stroke, neuropathy

Question 26

typical angiogenesis

Answer 26

endometrial growth, tissue regeneration

Question 27

initiation stimulus of physiological angiogenesis

Answer 27

Metabolic demands - exercising Developmental signal Controlled hypoxia

Question 28

initiation stimulus of pathological angiogenesis

Answer 28

Chronic inflammation Metabolism dysregulation Persistent hypoxia

Question 29

Key Signalling Pathways of physiological angiogenesis

Answer 29

Balanced VEGF regulation with coordinated pro- and antiangiogenic mediators

Question 30

key signalling pathways of pathological angiogenesis

Answer 30

Overactive VEGF signalling with imbalanced cytokines and dysregulated pro- and antiangiogenic mediators

Question 31

endothelial cell behaviour of physiological angiogenesis

Answer 31

Ordered sprouting, coordinated proliferation, regulated pericyte recruitment, and controlled vessel maturation

Question 32

endothelial cell behaviour of pathological angiogenesis

Answer 32

Chaotic sprouting, excessive proliferation, erratic migration, and abnormal cell-cell junctions

Question 33

vessel structure and function in physiological angiogenesis

Answer 33

well-organized vascular networks with proper arterial-venous identity and normal permeability

Question 34

vessel structure and function in pathological angiogenesis

Answer 34

disorganized, tortuous vessels with irregular diameters, excessive branching and leaky vessels

Question 35

2 compartments of solid tumors

Answer 35

the malignant cells and the stroma

Question 36

4 components of stroma

Answer 36

New blood vessels, inflammatory cells, connective tissues and fibrin-gel matrix

Question 37

tumor angiogenesis

Answer 37

Tumor cells release VEGF (hypoxia response)→ ↑ pathological angiogen → ↑ permeability and ↓ selectivity of neovascular fenestrated endothelium

Question 38

cancer treatments that target VEGF/R

Answer 38

Bevacizumanb (Anti-VEGF) Afiliberecept (VEGF trap) Ramucirumab (Anti-VEGFR2)

Question 39

cancer treatments that inhibit tyrosine kinases

Answer 39

sunitinib, sorafenib, pazopanib

Question 40

ischemia angiogenesis treatment

Answer 40

stem cell therapy: injection of stem cell into the diseased area to promote vessel formation by increasing HIF-1a, VEGF and eNOS VEGF signalling target: increases VEGFR activation and HIF1a signaling

Question 41

Limitations of ischemia angiogenesis treatment

Answer 41

* Risk of excessive VEGF production and vascular leakage * Concerns about long-term safety due to potential pro-tumorigenic effects * Limited central nervous system penetration of some compounds (for ischemic stroke or vascular dementia)

Question 42

vascular dementia

Answer 42

caused by reduced blood flow and reduction of vessel in the brain cauing neuronal damage