Ch. 8

Question 1

What are the 5 classes of receptor proteins?

Answer 1

• G-protein coupled receptors (GPCR)
• Receptor tyrosine kinases (RTK)
• Tumor necrosis factor receptors
• Nuclear receptors
• Ligand-gated ion channels

Question 2

What are nuclear receptors?

Answer 2

• Intracellular receptors (hydrophobic)
• Not bound to membrane
• Serves are transcription factors that regulate gene expression

Question 3

What are the steps of cell signaling that use membrane-bound receptors?

Question 4

What are the steps of cell signaling that use nuclear receptors?

Question 5

What are the results of cell signals?

Question 6

How could you a Western to detect steps of cell signaling?

Question 7

How could you use coimmunoprecipitation or immunoprecipitation with respect to cell signaling ?

Question 8

How are Northern vs Western techniques applied to cell signaling?

Answer 8

Northern
- Specific RNAs (separate RNA by size)
- After electrophoresis and transfer to membrane paper and use nucleic acid probe

Western
- Specific protein (denatured, not native)
- Use antibody after SDS PAGE and transfer to a membrane

Question 9

Compare and contrast endocrine, paracrine and autocrine signaling.

Answer 9

• Endocrine: near
• Paracrine: far
• Autocrine: self

Question 10

What is endocrine signaling?

Answer 10

A hormone secreted into the circulatory system by a gland that can bind to a receptor protein on a target cell

Question 11

What is paracrine signaling?

Answer 11

A hormone that functions over short distances to activate receptors on NEARBY cells

Question 12

What is autocrine signaling?

Answer 12

A hormone that functions over short distances to activate receptors on the SAME TYPE of cell

Question 13

What are first messengers?

Answer 13

• Extracellular ligands the bind to receptor proteins
• Categorized as endocrine, paracrine, autocrine

Question 14

List examples of first messengers.

Answer 14

Hormones: biologically active compounds that are released into the circulatory system and come into contact with hormone receptors in target cells

Question 15

What are second messengers?

Answer 15

Small, nonprotein intracellular molecules that amplify receptor-generated signals

Question 16

List examples of second messengers.

Answer 16

• cGMP
• cAMP
• DAG
• IP3
• Ca2+

Question 17

What 3 secondary messengers come from glycerophospholipid cleavage? End result?

Answer 17

• DAG
• IP3
• ???

Question 18

What are the steps of the GPCR signaling pathway?

Answer 18

1. Ligand-induced conformational changes in the GPCR
2. Receptor-mediated stimulation of guanine nucleotide exchange (GTP replaces GDP)
3. Regulation of downstream effector processes by Ga-GTP and GBy complexes
4. Termination of signal

Question 19

What are the steps of the RTK signaling pathway?

Answer 19

1. Transmits extracellular signals by ligand activation of an intrinsic tyrosine kinase function found in cytoplasmic tail of the receptor
2. Activated RTKs are dimers, which phosphorylate themselves before adaptor proteins link them to GEF for RAS
3. Phosphorylate downstream signaling proteins that bind to RTK phosphotyrosines

Question 20

How do ligand gated channels work?

Answer 20

Control the flow of of K+, Na+, and Ca2+ ions across the cell membrane in response to ligand binding

Question 21

What is protein kinase A?

Answer 21

• Active when cAMP levels are hgih
• Leads to three distinct metabolic responses:
  1. Phosphorlyation and inhibition of glycogen synthase; impedes glycogen synthesis
  2. Phosphorlyation and activation of enzymes involved in glycogen degradation to produce glucose
  3. Phosphorylation and activation of enzymes involved in gluconeogenesis (glucose from citric acid cycle intermediate and pyruvate)

Question 22

What is phospholipase C?

Answer 22

A membrane-associated enzyme that hydrolyzes PIP2 to form DAG and IP3

Question 23

What is GEF?

Answer 23

• Guanine nucleotide exchange factor
• Promote GDP-GTP exchange
• Activate signaling

Question 24

What is GAP?

Answer 24

• GTPase activating proteins
• Stimulate intrinsic GTP hydrolysis activity
• Inhibit signal transduction

Question 25

What are the 3 subunits of trimeric G proteins and which nucleotides bind when active vs inactive?

Answer 25

• α, Gβ, and Gγ subunits
• ???

Question 26

How is Insulin involved in cell signaling and what pathway?

Answer 26

• Insulin (ligand) binds to the insulin receptor and induces a conformational change
• Insulin contains two chains, which are held together by disulfide bonds

Question 27

How is cell signaling involved in cancer?

Answer 27

• The most common oncogenic Ras mutation lead to defects in the intrinsic GPTase activation and thereby block Ras protein inactivation. Dominant Ras mutations in the GTPase domain lead to chronic stimulation of the MAP kinase signaling pathway, even in the absence of growth factors