Biosignaling Q5

Question 1

Explain how the following signaling systems work: Autocrine, Paracrine, Synaptic, Endocrine.

Answer 1

Autocrine works on itself. Paracrine is usually working within an organ system. Synaptic is within synapses. Endocrine is largest domain and is released into vasculature and travels to effector organ.

Question 2

What are the four components of signal transduction?

Answer 2

1- signal, 2- receptor, 3- transduction pathways, 4- targets.

Question 3

What are the soluble signals and give an example of each.

Answer 3

Proteins and amino acids like epidermal growth factor. Lipids and fatty acids like ceramide and testosterone. Carbohydrates like glucose.

Question 4

What is a linked signal and give an example.

Answer 4

Usually integrated into plasma membrane like integrin.

Question 5

What are the physical signals and give example of each.

Answer 5

Mechanical, mechanoreceptors. Light, opsin. Temperature, TRP channels.

Question 6

How does G protein- coupled receptor work?

Answer 6

External ligand binding to receptor activates G protein which regulates enzyme responsible for second messenger.

Question 7

How does receptor tyrosine kinase work?

Answer 7

Ligand binding activates tyrosine kinase by autophosphorylation activating transcription factor

Question 8

How does receptor guanylyl cyclase function?

Answer 8

Ligand binding to extracellular domain stimulates formation of second messenger cyclic GMP.

Question 9

How does gated ion channel work?

Answer 9

Opens in response to concentration of ligand or membrane potential.

Question 10

How does adhesion receptor work?

Answer 10

(Note integrin) binds molecules in ECM changes conformation altering interaction with cytoskeleton.

Question 11

What is the dissociation constant (Kd)?

Answer 11

Concentration of ligand at which 50% of receptors are bound by ligand.

Question 12

What are the major role for plasma membrane in signaling?

Answer 12

1- receptor location, 2- Ligand exposure for receptor, 3-signaling complex information, 4- endocytosis.

Question 13

What is one of the benefits when using endosomes for signal transduction?

Answer 13

Allows for signal to stay active by increasing concentration and therefore increasing binding.

Question 14

What are the two types of lipid rafts?

Answer 14

Caveolar and planar.

Question 15

How can lipid rafts encourage promotion or inhibition of signals?

Answer 15

Promotion by organizing receptors and effectors in lipid rafts and inhibition by separating them.

Question 16

What structure is responsible for placing receptors back onto membranes?

Answer 16

Recycling endosome.

Question 17

What structure is responsible for sorting and sending things to the various vesicles?

Answer 17

Golgi.

Question 18

What is responsible for sending things to a lysosome?

Answer 18

Late endosome.

Question 19

How are things transported to the nucleus?

Answer 19

Through gated transport.

Question 20

What protein is responsible for directing traffic along the vesicular pathways?

Answer 20

Rab GTPase protein.

Question 21

What are some of the postranslational modifications and what are they useful for?

Answer 21

Phosphorylation, ubiquitination, glycosylation, oxidation, methylation, acetylation, SUMOylation. Used for allosteric regulation of enzymes.

Question 22

What are the 4 common signaling cascades?

Answer 22

1- mitogen-activated protein kinase (MAPK this is the most common) 2- Janus kinase- signal transducer and activator of transcription (JAK-STAT) 3- Phosphatidylinositol 3-Kinase (Pi3K) 4- Phospholipase C (PLC)

Question 23

What is the basic outline of MAPK signaling?

Answer 23

RAS activates MAP kinase kinase kinase, activating MAP kinase kinase, activating MAP kinase which acts on various proteins and regulators. Each activation step takes ATP.

Question 24

What is the basic outline of JAK-STAT signaling?

Answer 24

JAK phosphorylates STAT at the membrane which then moves into the membrane activating transcription.

Question 25

What is the basic outline for PI3K signaling?

Answer 25

PI3 kinase phosphorylates PIP2 to PIP3 which then is able to phosphorylate AKT which is able to act on a number of other things like protein synthesis and cell death.

Question 26

What is the basic outline for phospholipase C signaling?

Answer 26

G proteins have three units which G alpha then activates phospholipase C.

Question 27

What is the idea of cross talk in signaling?

Answer 27

The idea that pathways influence each other.

Question 28

What are the most common targets for cell signaling?

Answer 28

Nucleus, actin/tubulin/filaments, enzymes, receptors, transporters, ion channels.

Question 29

What types of signaling does epinephrine signaling utilize?

Answer 29

G-protein and PLC signaling.

Question 30

What types of signaling does insulin signaling utilize?

Answer 30

RTK, MAPK, PI3K.

Question 31

What are the responses of epinephrine binding compared to binding with epinephrine and norepinephrine?

Answer 31

With epinephrine you will get smooth muscle relaxation and vasodilation where with the two binding you will get smooth muscle contraction and vasoconstriction. The first uses B-adrenergic receptor and the second uses A1-adrenergic receptor.

Question 32

What is the basic signaling pathway for MAPK in insulin?

Answer 32

insulin binds to receptor causing tails to be autophosphorylated. IRS 1 comes in and is phosphorylated and then recruits RAS leading to activation of MAPK.

Question 33

How is the PI3K signaling done in insulin?

Answer 33

IRS-1 activates PI3K with phosphorylation activating the GS proteins synthesizing glycogen.