Receptors

Question 1

What types of receptors are there in terms of cell specificity?

Answer 1

Cell type specific and cell specific.

Question 2

Give the cell specific types of receptors?

Answer 2

Contact-dependent and synaptic.

Question 3

What are the three types of receptors?

Answer 3

Enzyme-coupled, ion channel coupled and G-protein coupled receptors.

Question 4

Which is the largest family of receptors with over 700 cell surface receptors?

Answer 4

G-protein coupled receptors

Question 5

What depends on G-protein coupled receptors?

Answer 5

Sight, smell and taste senses, many signal from the external environment but also other cells.

Question 6

What act on G-protein coupled receptors?

Answer 6

Proteins, small peptides, derivatives of amino acids and fatty acids, photons of light and all the molecules we smell/taste.

Question 7

What structure do G-proteins coupled receptors have?

Answer 7

A single polypeptide chain that threads across the membrane several times- highly conserved.

Question 8

What do G-protein coupled receptors use to relay the signal in the cells interior?

Answer 8

A G-protein as a secondary messenger.

Question 9

What disease is caused by a mutation in the parathyroid hormone receptor in the kidney?

Answer 9

Jansen’s metaphyseal chondrodysplasia (short limbed dwarfism)

Question 10

What does the mutation in the parathyroid hormone cause?

Answer 10

Constitutive activation of the receptor which leads to poor regulation of calcium and phosphorous concentration and chondrocyte growth.

Question 11

What diseases are associated with the thyroid stimulating hormone receptor?

Answer 11

Grave’s disease and Hashimoto’s

Question 12

What is cell communication vital for?

Answer 12

Spatial patterning, allows distal communication, cell proliferation, apoptosis, differentiation, cell guidance and maturation.

Question 13

Describe Grave’s disease?

Answer 13

Causes hyperthyroidism due to agonistic autoantibodies which effect the thyroid stimulating hormone receptor chasing excess cAMP production.
Symptoms include weight loss, goitre, opthalmopathy etc.

Question 14

Describe Hasimoto’s disease?

Answer 14

Caused by antagonistic antibodies resulting in less cAMP production.
Symptoms include weight gain, often post partum.

Question 15

How does cholera toxin use hosts receptors?

Answer 15

Uses ganglioside Gm1 to enter and it’s result effects cAMP production

Question 16

How does pertussi toxin use the host receptors?

Answer 16

Prevents activation of Gai via ADP-ribosylation leading to increase in cAMP effecting ion influx into the lung epithelial cells.

Question 17

What is McCune-Albright Syndrome?

Answer 17

Activating Gsa mutations cause over activation. Two main mutations: Arg201 in the GTP/GDP binding domain of the protein which is the cholera toxin binding site and Gln227 required for intrinsic GTPase activity.

Question 18

What is the café-au-lait phenotype?

Answer 18

A non-germline (somatic) defects phenotype. Increased in melanocytic-stimulating hormone-Gs-cAMP pathways causes stimulation of melanin pigment production.

Question 19

What is the fibrous dysphasia osteoblasts dysfunction?

Answer 19

Bone dysfunction

Question 20

What is pseudohypoparathyroidism?

Answer 20

Caused by a loss in GNAS function, essential for parathyroid signalling. Has different phenotype a dependent on whether it is inherited maternally or paternally.

Question 21

What are the six classes enzyme-couple receptors?

Answer 21

Receptor tyrosine kinases, tyrosine kinase associated receptors, receptor threonine/serine kinases, histidine kinase associated receptors, receptor quanylyl cyclase receptors, receptor like tyrosine phosphatases.

Question 22

What is the structure of enzyme-coupled receptors?

Answer 22

Transmembrane proteins that have a ligand-binding domain on the outer surface of the plasma membrane. They have a cytosolic domain which has intrinsic enzyme activity or associated directly with the enzyme.

Question 23

How do enzyme-coupled signal?

Answer 23

Via a phosphorylation cascade, have many growth factors: VEGF, EGF, M-CSF, ephrin and insulin receptors.

Question 24

How does a receptor tyrosine kinase act after ligand binding?

Answer 24

Cross phosphorylation their cytoplasmic domain on multiple tyrosine. Trans-autophosphorylation stimulates the kinase and produces a set of phosphotyrosine that serve as docking sites for a set of intracellular signalling proteins which bind via their SH2 or PTB domains. Ras-GEF is activated which activates the monomeric GTPase Ras, which activates a 3 part MAP kinase pathway.

Question 25

What is insulin receptors main role?

Answer 25

To increase glucose uptake

Question 26

What does the insulin receptor do in diabetes?

Answer 26

Becomes desensitisation: endocytosis and degradation receptor due to phosphotyrosine phosphatases (PTPases), down modulation of P13K and IRS proteins (both downstream signalling components)by high glucose and free fatty acids.

Question 27

What receptors do all multicellular organisms require?

Answer 27

Adhesion receptors

Question 28

What adhesion receptors allow?

Answer 28

Spatial patterning, migration, differentiation, guidance, morphogenesis, cell-to-cell and cell-to-matrix interactions. Some mediate homotypic interactions and some heterotypic.

Question 29

What are the types of adhesion receptors?

Answer 29

Ig superfamily, Cadherin, intergrins, selectins, proteoglycans.

Question 30

Describe the leukocyte adhesion cascade?

Answer 30

1. Capture: mediated by selectins
2. Rolling: mediated by selectins
3. Self rolling: mediated by selectins, activated by chemokines
4. Arrest: mediated by integrins
5. Adhesion, strengthening and spreading
6. Intravascular crawling
7. Paracellular transmigration
8. Transcellular transmigration

Question 31

What is a disease caused by migration defects in neutrophils?

Answer 31

Leukocyte adhesion deficiency (LAD), causes recurrent infections.

Question 32

In LAD1, 2 and 3 what is deficient?

Answer 32

LAD1: CD18 (a crucial integrin)
LAD2: fucosyl transferase (important for generating selectin ligands)
LAD3: activation of integrins

Question 33

What embryonic processes involve cell-adhesion?

Answer 33

Segregation of tissues during neural tube formation, dispersion of cells from a solid tissue, migration of cells allow adhesive guidance cues, cavity formation and cell-to-call communication through gap junctions.

Question 34

What is metastasis?

Answer 34

The spread/movement of cancer cells from one organ or tissue to another via the blood stream or lymph system.

Question 35

What are microbial receptors?

Answer 35

Receptors of the immune system which need to be able to recognise self and non-self.

Question 36

What type of microbial receptors have evolved and what do they do?

Answer 36

Surface pattern recognition receptors, which recognise various pathogen associated molecular patterns (PAMPs). They are able to signal to produce appropriate responses and produce various cytokines and immune regulators.

Question 37

What are the major types of surface pattern recognition receptors?

Answer 37

Toll receptors and carbohydrate binding lectins.

Question 38

What defects in surface pattern recognition receptors are there?

Answer 38

Toll mutant drosophila or candida infection.

Question 39

How do listeria pathogens exploit host receptors?

Answer 39

CD4 on T cells normally interacts with MHC2 on APCs leading to activation of T helper cells, allowing the hydrophobic fusion protein to be inserted into the membrane but listeria exploits phagocytic receptors to enter the cell.