There are so many hormones/cytokines/neurotransmitters and receptors, all of which act through about 4-5 second-messenger systems. So if one particular cell has receptors for say, two different hormones which act via the same second messenger, is there any way that the cell can distinguish the two stimuli? I’m guessing there must be some distinguish between the two, otherwise, wouldn’t the effect of both the hormones be the same?

For example, in a hepatocyte, beta-adrenergic receptors and glucagon receptors both act via Gs-coupled receptors, downstream of which, cAMP is increased. Since the cAMP is the same, the changes it would make are also the same. So does it to the hepatocyte, make no difference if the first messenger was epinephrine or glucagon?

I’m assuming the receptors would make a difference, but aren’t the coupled G-proteins (Gs) also the same? Is there a difference of amplitude?

Note: I understand that it is not necessary for the hormones to produce an exclusively different effect. I also understand that systemic effects can be different because of differential distribution of receptors. My question pertains to the effects on a single cell.

  • $\begingroup$ Technically, yes. But signalling molecules/receptors often elicit multiple responses. $\endgroup$
    Jan 17 '17 at 9:31
  • $\begingroup$ Thanks @wysiwig could you pls give an example? $\endgroup$
    – Polisetty
    Jan 17 '17 at 11:58
  • $\begingroup$ Here is some further discussion on the question reddit.com/r/Biochemistry/comments/5pig7x/… $\endgroup$
    – Polisetty
    Jan 23 '17 at 20:23
  • $\begingroup$ Sorry. I just forgot. I'm a bit occupied right now. Will get back. Ping me if I forget again. $\endgroup$
    Jan 24 '17 at 4:06
  • 1
    $\begingroup$ Perhaps an interesting read with an example is the following: ncbi.nlm.nih.gov/pubmed/24365330 Two ligands (LH and hCG) binding the exact same receptor, yet differing in their actions. Part of the difference is mediated via the second messenger they share (cAMP). $\endgroup$
    – pbond
    Jul 26 '17 at 0:35

Secondary signaling molecules like cAMP, Calcium, and Ras-Raf are common in many pathways and I think its a way of integrating different signals.We cannot say that at a moment only one pathway operates in a cell or a single pathway will be enough for a process to happen.I think common second messengers is a resource and time-saving method adapted by our system to coordinate different response efficiently.https://www.nature.com/scitable/topicpage/cell-signaling-14047077

Then how a cell can identify which pathway and process should go on? I think that each time this second messenger will make a small change in choosing down stream effectors.Like Calcium binds to calmodulin which in turn choose next binding partner.Maybe the number of second messengers like concentration and affinity decide which downstream effector will be appropriate for the required stimuli.You can see in this link about how different secondary messengers make different results https://www.ncbi.nlm.nih.gov/books/NBK9870/

About GPCR, more than 800 GPCR are there and you can see from this link http://jcs.biologists.org/content/116/24/4867

So, Do two hormones have the same effect on a cell if the second messenger is the same? I think yes, see this table (https://www.ncbi.nlm.nih.gov/books/NBK21705/) enter image description here

Here, from the table, you can see adrenaline and glucagon are having the same effect in the liver cell and both have cAMP as a second messenger.But in cardiac muscle and intestine, adrenaline is having a different function. So I think it depends on the cell also.

  • $\begingroup$ So is your answer to the poster’s question Yes or No? And why exactly? $\endgroup$
    – David
    Mar 21 '18 at 13:32
  • $\begingroup$ I think yes, for details you can see my edited answer.Thank you $\endgroup$
    – Sarannya E
    Mar 22 '18 at 7:38

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