Signaling

Question 1

common features of signaling pathways (6)

Answer 1

reception, discrimination, info transfer, amplification, adaptation and integration

Question 2

what receives signalling ligand in pathways?

Answer 2

usually receptor protein, either on cell-surface or intracellular

Question 3

what does signaling discrimination mean?

Answer 3

only certain signals are capable of activating a given pathway

Question 4

T/F. The form of signaling information can change throughout a pathway.

Answer 4

True. Chemical energy can be transduced into electrical energy, for example.

Question 5

What is the process of signalling adaptation?

Answer 5

when you are continually exposed to a signal, the activity through that pathway decreases

Question 6

why is amplification important?

Answer 6

sensitivity to signals, which may be present in vanishingly small concentrations - but which are still very important

Question 7

how are signal transduction processes classified?

Answer 7

1) type of signal - chemical (small molecules, carbs, peptides) vs physical (electromagnetic, thermal, mechanical)
2) type of signal transduction molecules involved
3) Site of detection (plasma membrane or intracellular)
4) Origin and route of signal - diffusible vs anchored signals

Question 8

cGAS

Answer 8

live with it

Question 9

how are diffusible signals broken down?

Answer 9

by distance they have to travel from production to target - endocrine are distant, paracrine are nearby (ie neuronal synapse), autocrine are detected by same cells that produce them

Question 10

what can receptors do (6)

Answer 10

1) bind ligand - saturable and specific
2) transduce signal across either plasma membrane or within cell
3) catalytic activity
4) complex with other subunits
5) experience occupancy-induced changes in activity
6) internalize ligand

Question 11

What are some ways receptors can complex with other subunits?

Answer 11

They can be constutively complexed, or inducibly.

They can be composed of the same types of proteins or different types.

Question 12

ligand binding assay - how do you overcome a small number of receptors per cell?

Answer 12

you can either use radioactive or fluorescent ligant, or overexpress recombinant receptor or purify native receptor

Question 13

ligand binding assay - how to overcome rapid dissociation of bound ligand from receptor?

Answer 13

could do rapid filtration and wash, or centrifuge through mineral oil - or rapid size exclusion chromatography

Question 14

ligand binding assay - what to do to make sure your ligand isn’t binding to non-receptor sites (nonsaturable)

Answer 14

competition with excess unlabeled ligand

Question 15

ligand binding assay - what to do to make sure your ligand isn’t binding to other receptors (nonspecific)

Answer 15

competition with excess site-specific ligand

Question 16

what are some ways to deduce receptor structure?

Answer 16

biochemical purification/characterization, cDNA cloning, primary sequence analysis of cDNA, topology mapping (protease accessibility), heterologous expression studies, structural analysis of purified receptor protein

Question 17

how can you tell what side of the plasma membrane the N/C termini of a receptor are on?

Answer 17

protease accessibility or epitope tagging

Question 18

what are some roles of adaptor molecules in signaling?

Answer 18

scaffolding, activation of effectors (enzymes or ion channels)

Question 19

effectors to know: adenylyl cyclase

Answer 19

ATP —> cAMP + PPi

Question 20

effectors to know: protein kinase

Answer 20

phosphorylates proteins on Seer/Thr or Tyr residues

Question 21

effectors to know: phospholipase C

Answer 21

PIP2 —-> Diacylglycerol + IP3

Question 22

effectors to know: nitric oxide synthase

Answer 22

arginine —-> citrulline + NO

Question 23

effectors to know: guanine nucleotide exchange factor

Answer 23

exchange of GTP for GDP on guanine nucleotide regulatory proteins

Question 24

effectors to know: ion channel

Answer 24

mediates ion flux across membranes

Question 25

effectors to know: ENA/VASP protein

Answer 25

regulates actin polymerization

Question 26

Testing

Answer 26

Testing

Question 27

chemiosmotic circuits can do what kind of work?

Answer 27

mechanical, chemical, and osmotic

Question 28

chemiosmotic circuits can do what kind of work?

Answer 28

mechanical (drive flagella), chemical (drive proton import), and osmotic (water import/export)

Question 29

initiator of chemiosmotic circuits

Answer 29

pumps

Question 30

chemiosmotic circuits are built on what type of ion?

Answer 30

protons in prokaryotes and lower eukaryotes, and sodium in higher eukaryotes (sodium-potassium ATPase)

Question 31

T/F. At E(K) equilibrium, ions are no longer translocating across the membrane.

Answer 31

False. Still translocation, just no net change

Question 32

What happened to concentration gradient getting to E(K)?

Answer 32

It doesn’t change, at least not significantly. You only need to lose a very small portion of ions (ex in class 0.25%), and decreases further as cell gets larger and larger

Question 33

T/F. Electrical potentials change at the same rate as concentration gradients

Answer 33

False, electrical potentials change faster than concentration gradients

Question 34

How do you create a concentration gradient?

Answer 34

Cells have to shunt their electrical potential, ex acidification of the lysosome or dissolution of bone during growth (pH gradient by V-ATPase)