Estradiol Recepetor Question

[moc1025]

Hi Guys!

I'm having trouble figuring out this question. I thought it was B but now Im not sure...any help would be appreciated!

Testosterone is converted to estradiol via aromatase, a member of the CYP450 family of enzymes. Estradiol receptors fall into two classes: ER (further divided into ERa and ERb) and G protein-coupled receptors (GPR30). Where are these receptors most likely to be located?

A. ERa and ERb are likely to be embedded in the cell membrane, and GPR30 is likely to be dissolved in the cytosol.
B. ERa and ERb are likely to be dissolved in the cytosol, and GPR30 is likely to be found embedded in the outer membrane of the nuclear envelope.
C. ERa and ERb and GPR30 are all likely to be found dissolved in the cytosol.
D. ERa and ERb and GPR30 are all likely to be found embedded in the cell membrane.

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[Cawolf]

Is B not the correct answer? It seems to be a good choice.

 

[moc1025]

Is B not the correct answer? It seems to be a good choice.

I don't know what the correct answer is. I thought B but I'm not sure so wanted to get other opinions

 

[Cawolf]

It is definitely B IMO.

 

[moc1025]

It is definitely B IMO.

Thanks! Would you mind explaining it briefly?

 

[Cawolf]

I will read your explanation and tell you if I agree or if I disagree - if I disagree I will explain why.

 

[moc1025]

I will read your explanation and tell you if I agree or if I disagree - if I disagree I will explain why.

Ok! Well at first I had no idea how to answer the question. My only hint was that estrogen is a steroid hormone so I figured the ER receptors would probably be in the cytosol since estrogen can pass through the nuclear membrane. Even though GPR30 is also an estradiol receptor the word protein made me think that this receptor would be in the cell membrane since protein hormones can't pass through the cell membrane. Therefore I got B.

 

[Cawolf]

Right - your thinking is correct.

Steroid hormones will pass into the cytosol where they can bind receptors or be transported into the nucleus.

Therefore, looking for the ER receptors inside the cell makes the most sense.

G-protein coupled receptors are membrane bound receptors than start a series of reactions when bound. These are the receptors than peptide hormones bind on the cell membrane - so looking for an answer choice where this receptor is membrane bound makes the most sense. This makes B the best choice.

 

[moc1025]

Right - your thinking is correct.

Steroid hormones will pass into the cytosol where they can bind receptors or be transported into the nucleus.

Therefore, looking for the ER receptors inside the cell makes the most sense.

G-protein coupled receptors are membrane bound receptors than start a series of reactions when bound. These are the receptors than peptide hormones bind on the cell membrane - so looking for an answer choice where this receptor is membrane bound makes the most sense. This makes B the best choice.

Great. Appreciate the help!

 

[joeylewis]

Hi guys, I do not think that this question is worded correctly. I assume this is for a Kaplan Technical Interview b/c they use this question. Here is my logic:

Back-ground:
-Steroids traverse the cell membrane and their receptors are typically associated with the nuclear receptors or cytoplasmic receptors whose hormone-receptor-complexes bind to DNA w/in nucleus
-Nuclear receptors are a large family of structurally related ligand-inducible transcription factors, which include ERa and ERb
-GPR30 is a member of the rhodopsin-like family of G protein-coupled receptors and is a multi-pass membrane protein that localizes to the endoplasmic reticulum.

I love Kaplan, in terms of challenges and headaches lol, but I'm having trouble with the term "dissolved"... How can one dissolve a protein and maintain its functionality? W/ all else in mind, I do agree with the above logic.

Thx

@moc1025 : I'm curious as to the correct answer from the question writers persepective.

Thanks, Joe

 

[Labrat07]

@joeylewis
For me, "dissolved" = soluble in that solution. Think of bond binding of monomer to the aquaeous solution molecules. It lose it 3d structure but it still as it functions. That's how I think about this concept anyway.

 

[Czarcasm]

Hi Guys!

I'm having trouble figuring out this question. I thought it was B but now Im not sure...any help would be appreciated!

Testosterone is converted to estradiol via aromatase, a member of the CYP450 family of enzymes. Estradiol receptors fall into two classes: ER (further divided into ERa and ERb) and G protein-coupled receptors (GPR30). Where are these receptors most likely to be located?

A. ERa and ERb are likely to be embedded in the cell membrane, and GPR30 is likely to be dissolved in the cytosol.
B. ERa and ERb are likely to be dissolved in the cytosol, and GPR30 is likely to be found embedded in the outer membrane of the nuclear envelope.
C. ERa and ERb and GPR30 are all likely to be found dissolved in the cytosol.
D. ERa and ERb and GPR30 are all likely to be found embedded in the cell membrane.

In order for G-Protein Coupled receptors to illicit their response, the activated G-protein must slide along a membrane to activate a membrane-bound enzyme. Knowing this would allow you to eliminate choice A and C (that its dissolved in the cytosol, which is not possible). Testosterone is a lipid-soluble molecule which can pass directly through the lipid bilayer, which must mean that the enzyme aromatase functions intracellularly to produce estradiol. Estradiol is water-soluble (hint: "diol") and is basically locked inside the cell at this point (it cannot penetrate the lipid bilayer). Therefore, the receptor for estradiol must be located somewhere in the cell making choice B the most logical answer.

 

[joeylewis]

@Labrat07 I like the term "soluble" in this case- I think that's a great way to frame the question! I think I was/am a bit fixated on the term "dissolve" or at least its potential implications. I do hesitate in making assumptions on any changes in the receptors 3-d structure as it is related intimately w/ its binding-site specificity. Blah, blah...