Cell signalling

# 3.4 Second messengers

In the previous section, we have discussed the principles of second messengers (Section 1.5) and, in particular, those produced by PLC (IP3 and DAG) and PI3 kinase (PI(3,4)P2 and PI(3,4,5)P3). We shall now consider the roles and mechanisms of action of the other chief mediators, which are Ca2+ ions, cAMP and cGMP. These are water-soluble second messengers.

Of the second messengers produced by PLC and PI 3-kinase, which ones are hydrophobic?

## Answer

PI 3-kinase products PI(3,4)P2 and PI(3,4,5)P3 and the PLC product DAG are hydrophobic. They contain fatty acyl chains that anchor them to the plasma membrane.

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