Cell Signaling

Question 1

What are the four modes of cell-to-cell signaling? Give examples of each.

Answer 1

• Endocrine
• Paracrine
• Autocrine
• Juxtacrine (contact dependent)

Question 2

What are 4 different types of chemical messengers?

Answer 2

• Endocrine system: glucagon, insulin, steroid hormones
• Growth factors: nerve growth factor, PDGF
• Nervous system: all of the neurotransmitters (ex. acetylcholine, GABA, NO, Carbon monoxide)
• Immune system: cytokines

Question 3

What are the 3 main classes of cell-surface receptors?

Answer 3

• Ion channel receptors
• Receptors that are kinases or bind kinases aka enzyme-linked receptors
• Heptahelical receptors- work thru second messengers (can open ion channels; activate adenyl cyclase which converts ATP to cAMP; activate phosphatidyl inositol which uses IP3, diacylglycerol, and Ca++ as 2nd messengers)

Question 4

What is the ryanodine receptor?

Answer 4

When this receptor is pharmacologically activated it can release too much Ca++, leading to a lot of ATP hydrolysis which produces heat. Thus, hyperthermia. Some anesthetics can bind to this receptor in certain people.

Question 5

What is the role of PKA and PKC?

Answer 5

PKA: activated by cAMP, transcription factor for gene regulatory proteins and many other target proteins

PKC: Activated by Ca++ & diacylglycerol, transcription factor for gene regulatory proteins and many other target proteins

Question 6

What are the intracellular events leading to activation of nuclear transcription via protein kinase A?

Answer 6

• Activated G-protein-linked receptor
• G protein
• adenylyl cyclase
• cyclic AMP
• activates PKA

Question 7

Compare ionotropic vs. metabotropic effectors.

Answer 7

Ionotropic: produce very quick responses by opening ion channels. Ex. nicotinic receptor causing muscle contraction

Metabotropic: take seconds, minutes, or hours to achieve result. Ex. cell proliferation. Mostly kinase activity

Question 8

Describe the activity of calmodulin.

Answer 8

Ca++ can bind to calmodulin, which converts inactive calmodulin to active calmodulin. This binds to protein kinase called calmodulin modulated kinase (CaM-Kinase).

Question 9

What is the relationship between IP3 and Ca++?

Answer 9

IP3 binds to and opens IP3-gated Ca++-release channels. This allows Ca++ to flow into the cell.

Question 10

What is the role of PI 3-kinase in signal transduction?

Answer 10

Phosphorylates PI 4,5 bisphosphate to create the docking site for pleckstrin homology domains.

Question 11

What is the gene in the Rous Sarcoma Virus that causes cancer in chickens?

Answer 11

Src gene

Question 12

What is the difference in the cellular response of the MAP kinase pathway vs. the heptahelical pathway?

Answer 12

The MAP kinase pathway is initiated usually by a tyrosine kinase type receptor and involves many protein kinases. The heptahelical pathway most often involves 2nd messengers.