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Signaling and receptors.

It might just be my vague and shallow knowledge of cellular signaling and receptors...

BUT

I keep hearing how cells use G protein coupled receptors, to activate adenyl cyclase or PLC for cell signalling, what i would like to know is that if so many different molecules can activate different receptors that all activate adenyl cyclase or PLC, which in turn creates cAMP or IP3, how does the cell differentiate these signals and respond with different effects?

(may not make sense......people understand what im saying?) :eek3:
Reply 1
Avatar for martin101
martin101
10
quite simple really, its a final common pathway that each receptor system is using. For the most part it is just the same G protein activating the same downstream component, just a different receptor bolted on that activates the G protein

Eg B2 adrenergic receptors and 5HT receptors both use the Gs G protein which couples to an adenyl(yl) cyclase. So thats how 2 totally separate signalling molecules activate the same pathway.
Actually he's got a good point - if they're using the same 2nd messenger - how is say one receptor being bound upregulating production of X enzyme but then another receptor being bound downregulating a completely different enzyme?
I'd never thought about it that deeply to be honest...
Reply 3
Avatar for joshwaah
joshwaah
OP
Philosoraptor
Actually he's got a good point - if they're using the same 2nd messenger - how is say one receptor being bound upregulating production of X enzyme but then another receptor being bound downregulating a completely different enzyme?
I'd never thought about it that deeply to be honest...


Yeh thats what i was trying to get at....
Reply 4
Avatar for martin101
martin101
10
Philosoraptor
Actually he's got a good point - if they're using the same 2nd messenger - how is say one receptor being bound upregulating production of X enzyme but then another receptor being bound downregulating a completely different enzyme?
I'd never thought about it that deeply to be honest...


Well actually if you think about it carefully its not all that complicated. The problem you are having (from what I can tell) is that two different receptors are acting through the same pathway to produce different effects. The answer is that these receptors are present on different tissues. Just going back to my B2 and 5HT example before. In a very broad sense adronergic and seretonergic mechanisms are going to be working most on different tissues - definately an overgeneralisation, but 5HT we tend to think in terms of CNS and NA/Adr we think more somatic (there are far more examples to the contrary than Id like).

So basically they are acting through a most probably evolutionarily conserved mechanism targeting some downstream effector molecule which is relevant/expressed differently between tissues. - cAMP does loads of stuff (to use my B2 5HT example again).
martin101
Well actually if you think about it carefully its not all that complicated. The problem you are having (from what I can tell) is that two different receptors are acting through the same pathway to produce different effects. The answer is that these receptors are present on different tissues. Just going back to my B2 and 5HT example before. In a very broad sense adronergic and seretonergic mechanisms are going to be working most on different tissues - definately an overgeneralisation, but 5HT we tend to think in terms of CNS and NA/Adr we think more somatic (there are far more examples to the contrary than Id like).

So basically they are acting through a most probably evolutionarily conserved mechanism targeting some downstream effector molecule which is relevant/expressed differently between tissues. - cAMP does loads of stuff (to use my B2 5HT example again).

Ahhhh... good point - the receptors are on different tissues...duh.

:redface:
Fluctuations in second messenger concentrations may also be localised to particular areas within a cell.

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