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What enables cells to respond to changes in the concentration of a signaling ligand ?

  1. May 15, 2011 #1
    "In chemical signaling, adaptation enables cells to respond to changes in the concentration of a signaling ligand (rather than to the absolute concentration of the ligand) over a very wide range of ligand concentrations. The general principle is one of a negative feedback that operates with a delay. A strong response modifies the machinery for making that response, such that the machinery resets itself to an off position. Owing to the delay, however, a sudden change in the stimulus is able to make itself felt strongly for a short period before the negative feedback has time to kick in." -Molecular cell biology ,bruce albert
    I don't understand this paragraph. can anyone clarify this ( best with example , even paraphrasing it may help) .... I have also searched the net, for negative feedback that operate in delay.... got nothing helpful.
    Any help will be highly appreciated.
     
  2. jcsd
  3. May 15, 2011 #2

    Pythagorean

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    Re: What enables cells to respond to changes in the concentration of a signaling liga

    There's all kinds of negative feedback with delay in biosystems. I'm not really sure of context, but this sounds like the desensitization of a ligand-gated channel. The language is kind of arbitrary, though.

    Could you provide more context? (chapter topic, perhaps, what kind of material are you looking at?)
     
  4. May 15, 2011 #3
    Re: What enables cells to respond to changes in the concentration of a signaling liga

    It was trying to explain how cell respond to change in ligand concentration rather than absolute concentration, in general terms. Yap it later talks about desensitization ... but I am unsure how "negative feedback with delay" works and wondering how it helps cell to respond to change in ligand concentration.

    I guessed the following may be the case, but I am not sure ... Please correct me if I am wrong.

    Suppose the concentration of ligand increase from C1 to C2 , as a consequence (after some intermediate steps) the target (protein or enzyme) increase or decrease it's activity and elicit the response. After certain delay because of negative feedback, the response come to a halt. At this point the existing level of ligand concentration is unable to elicit a response.
    But when ligand concentration increases still, it push the existing static state resulted from some sort of equilibrium- toward a response... but eventually the negative feedback take over and halt the response.
    I also assume the negative feedback is strongly coupled with the ligand concentration... that is when ligand concentration falls it also withdraw certain extent of negative feedback inhibition.
     
    Last edited: May 15, 2011
  5. May 15, 2011 #4

    Pythagorean

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    Re: What enables cells to respond to changes in the concentration of a signaling liga

    Ok, now it sounds like you're talking about allosteric modulation, whereby the gate had a second, inhibitory binding sit for non-ligand (i.e. for allosteric modulation)

    I think, if the local concentration of ligand changes, it changes the energy landscape of the protein, which changes the on-off rates of allosteric modulators.
     
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