Looking at Lithium: Molecular Moods and Complex Behaviour

The phosphatydilinositol cycle in signal transduction. G protein–coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) mediate the activation of phospholipases C–(PLC)-β and -γ), which cleave phosphoinositide bis- phosphosphate (PIP₂) to yield diacylglycerol (DAG) and inositol trisphosphate (IP₃). DAG and IP₃ activate protein kinase C (PKC) and release calcium [Ca²⁺ ]_i from intracellular stores, respectively. IP₃ is rapidly hydrolyzed to inositol bisphosphate (IP₂) and inositol monophosphate (IP). Inositol monophosphatase-(IMAP)-1 and -2 hydrolyze IP to regenerate myoinositol. Inositol gains access to the cellular cytoplasm via uptake by the sodium/inositol cotransporter (SMIT1).