3 minutes seems a bit early. It will take a couple minutes for the signaling pathway to be activated, for the transcription factor to bind the DNA and for transcription to initiate. Then transcription happens at a certain rate (80bp/sec?), then the mRNA must be processed, exported to the cytosol, and translation initiation (the rate limiting step of translation) must occur. Then translation elongation (20aa/sec?) must occur. Then each mRNA must be translated multiple times until you have enough molecules of the protein to be detectable by Western (1ng at least). The biggest factor in whether you will see differences by qPCR and western at early time points will likely be the basal level of the mRNA and protein you are studying. If the levels are essentially at zero and you activate transcription, you might see something appear by western if you have a very sensitive antibody. If you're looking for the levels of an abundant protein or mRNA to change, you'll have to start calculating degradation/decay rates etc.

For some practical examples, you can look at SOCS proteins in response to interferon…generally people don't see any protein by western before 30 minutes.

I'm sure some amount of transcription and translation will continue to occur while you are collecting your samples, though.

I would do a time course of 10, 30 & 60 minutes for mRNA and wait at least 1 hr (or do a time course of 1, 2 and 4 hrs) for protein expression by westerns.

Thanks very much Mark and Subhadeep.

I have got some differences in Adiponectin production after 3 minutes of insulin stimulation but I am not sure if this is experimental or just really quick enough to happen in 3 minutes.

Fahrettin, I'm in full agreement with Mark Livingstone's comments. I'll just add that when I looked for SOCS3 protein after IL6 treatment of primary cultures of astroglia and microglia I observed protein as early as 15 minutes by WB, by overexposing the film. Maximal levels of SOCS3 occurred between 15 and 45 minutes.  So, at the very least you can say that LIgand to protein takes less than 15 minutes, and if you aren't restricted by the lower limit of detection of your technique you can probably bet that this all takes much less than 15 minutes.

Seems to me that there are two ways to interpret your question: 1) How long does this process (ligand to protein) actually take; and 2) How long after applying my ligand can I detect the mRNA and/or protein? I believe there a fair amount of work in attempting to answer the first question is being done using fluorescence based techniques. The second question is really all about the sensitivity of your technique and the abundance of your molecule of interest. Although I have attempted to provide you with my insight into the second question, I would also be very interested in knowing the answer to the first question.

Best.

Hi, all of you, interesting question! any reference please? Thanks!

Hi - this is an interesting question which I was interested in working gout. Does one think that if you applied a constant stimulus for 6 hours - or even 3 to a cell you would see alteration of protein expression after 6 hours? Or would it take longer? 12/24..?

Dear All,

At the moment I'm very interested about this (these) issue (s) . After reading a few articles, I concluded that these questions are not so simple. It seemed to me that we should look individually to the stimulus (which, intensity and time) and the target (cell type). 

In my case, I also like to know how long will last the response to the stimulus, ie, there will be an adaptation? It ceases to terminate the stimulus?

Well, here 1 reference I believe can help.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2864715/

Regards from Brazil.

Thanks for the article suggestion Guilherme, I will have a look forsure!