Module 2: Figure metabolic messengers

Interaction between metabolic messengers and cell signalling pathways.

A number of metabolic intermediates can interact with various cell signalling pathways. ATP plays a significant role through its ability to close ATP-sensitive K+ channels as occurs in insulin-secreting β-cells (Module 7: Figure β-cell signalling). ATP that is released from the cell functions to activate ATP-sensitive P2X channels (Module 3: Figure P2X receptor structure). ATP may also play an important role in regulating the activity of ADP-ribosyl cyclase that produces the Ca2+-mobilizing messengers cyclic ADP-ribose (cADPR) and nicotinic acid–adenine dinucleotide phosphate (NAADP) (Module 2: Figure cADPR/NAADP function). AMP is an important activator of the AMP signalling pathway (Module 2: Figure AMPK control of metabolism). The breakdown product of cADPR is ADP-ribose (ADPR), which is an activator of the transient receptor potential melastatin 2 (TRPM2) channel. Bicarbonate (HCO3) is an activator of soluble adenylyl cyclase and thus contributes to the cyclic AMP signalling pathway (Module 2: Figure cyclic AMP signalling).