BIOMG 1350 Lecture Notes - Lecture 15: Glycogen Phosphorylase, Phosphorylase Kinase, Lipid Signaling

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fuchsiadog160

28 Oct 2016

School

Cornell University

Department

Molecular Biology and Genetics

Course

BIOMG 1350

Professor

Huffaker

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Document Summary

G-protein coupled receptors (gpcrs) largest family of cell surface receptors (>700: 7 pass transmembrane proteins, wide variety of signaling molecules that can activate, ~1/3 drugs used today act through gpcrs. Gpcrs activate g proteins: trimeric g proteins (3 subunits) Beta, gamma covalently attached lipid tails to membrane. Alpha bound to gdp: signal molecule interacts with gpcr, gpcr changes conformation on cytosolic side of protein. Site for bonding for g protein: activated receptor acts as a gef for its g protein. Gdp associated from alpha: alpha will then bind gtp activated. Releases from receptor and dissociates from beta-gamma subunit. Can stay together, depends on type of g-protein: effector activation. Receptor can activate many molecules of g protein. G protein alpha subunit switches itself off: signal molecule stops being sent, hydrolysis of gtp by subunit inactivates subunit within seconds (helped by rgs) Goes back to gpcr to get reactivated (gdp displacement, gtp bind: causes it to dissociate from target protein.

Related Questions

You decide to complete a summer undergraduate research project in a lab that studies G-Protein coupled receptor (GPCR) signaling. The laboratory you join has identified two new GPCRs, GPCR-A and GPCR-B. The same ligand binds each receptor, but two different heterotrimeric G-proteins are activated that regulate adenylyl cyclase. A. You find that activation of GPCR-A causes an increase in adenylyl cyclase activity, while activation of GPCR-B causes a decrease in adenylyl cyclase activity.

B. You have a cell line that expresses both GPCR-A, GPCR-B, the corresponding G proteins and adenylyl cyclase. There is a basal level of adenylyl cyclase activity that produces a baseline cAMP concentration. Your project is to characterize a series of mutations in these components. Will each mutation increase or decrease the intracellular levels of cAMP upon ligand addition (remember, both GPCR-A and GPCR-B bind the same ligand)?

a. A mutation in GPCR-A that prevents G-protein activation

b. A mutation in GPCR-B that prevents G protein activation

c. A mutation in Gsa that prevents release of bound GDP

d. A mutation in Gia that prevents GTP hydrolysis

EXPLAIN your thought process and why each one was answered as increase or decrease

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QUESTION 1

Which of the following is an example of an extracellular signal molecule?

	a.	IP₃
	b.	cAMP
	c.	Insulin
	d.	Diacylglycerol

2 points

QUESTION 2

Nuclear hormone receptors _____

	a.	Bind to water soluble ligands
	b.	Activate second messengers
	c.	Regulate transcription in response to ligand binding
	d.	Are normally located on the plasma membrane

2 points

QUESTION 3

Which of the following does not occur when a receptor tyrosine kinase is bound by ligand?

	a.	Phosphorylation of the RTK
	b.	Cytoplasmic proteins bind the phosphorylated RTK
	c.	Dimerization of the RTK
	d.	The RTK binds to DNA to regulate transcription

2 points

QUESTION 4

Which of these is a logical signal-transduction pathway?

	a.	An intracellular receptor activates phospholipase C, which cleaves a membrane protein to form IP₃, which then activates the opening of an ER channel protein, which releases cyclic AMP into the cytoplasm, where it binds to an intracellular enzyme that carries out a response.
	b.	A G-protein-linked receptor activates G protein, which activates phospholipase C, which cleaves a membrane lipid to form IP₃, which binds to a calcium channel on the ER, which opens to release calcium ions into the cytoplasm, which bind to an intracellular enzyme that carries out a response.
	c.	An ion-channel receptor opens, allowing a steroid hormone to enter the cell; the steroid hormone then activates protein kinases that convert GTP to GDP, which binds to an intracellular enzyme that carries out a response.
	d.	A tyrosine-kinase receptor activates adenylyl cyclase, which activates phospholipase C, which converts ATP into cyclic AMP, which binds to an intracellular enzyme that carries out a response.

2 points

QUESTION 5

Which of the following is an example of signal amplification?

	a.	activation of an enzyme molecule
	b.	activation of a specific gene by a growth factor
	c.	Breakdown of many cAMP molecules
	d.	activation of 100 molecules by a single signal binding event

2 points

QUESTION 6

Consider a signal transduction pathway that utilizes cAMP as a second messenger to activate PKA (Protein Kinase A). Which of the following situations will result in the cellular response?

		The G protein releases GDP and binds to GTP
		The target protein (adenylyl cyclase) is inactive
		The regulatory subunits of PKA (Protein Kinase A) are bound to the catalytic subunits
		The appropriate G protein is bound to GDP

2 points

QUESTION 7

Which of the following is found in only some signal transduction pathways? [In other words, which is not found in all signal transduction pathways?]

		Receptor protein
		Extracellular signal molecule
		Intracellular signaling molecule
		Cellular response
		Effector protein

2 points

QUESTION 8

The enzyme that specifically catalyzes the conversion of ATP to cAMP is:

		Adenylyl phosphatase
		Adenylyl kinase
		Adenylyl dehydrogenase
		Adenylyl cyclase

2 points

QUESTION 9

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?

		It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
		It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
		It would employ a transduction pathway directly from an external messenger.
		It would be able to carry out reception and transduction but would not be able to respond to a signal.

2 points

QUESTION 10

A hormone signal is sent from the brain to other parts of the body via the bloodstream. Why do only certain cells respond to this signal?

		Hormones do not last long enough in the bloodstream to stimulate a cellular response
		Only cells that have a specific transcription factor gene will be able to respond to the signal
		Only cells in the immediate vicinity of the cell sending the signal will respond
		Only cells that have a receptor for the specific signal will be able to respond to it

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BIOMG 1350 Lecture Notes - Lecture 15: Glycogen Phosphorylase, Phosphorylase Kinase, Lipid Signaling

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