Gq-coupled protein receptor
The Gq-protein activates the enzyme phospholipase C (PLC) in the cell membrane. This enzyme converts phosphatidyl diphosphate (PIP2) into diacylglycerol (DAG) and inositol triphosphate (IP3). IP3 is responsible for the increase of intracellular calcium levels. The increased calcium concentration and the other second messenger (DAG) both activate protein kinase C (PKC). Phosphorylation of PKC is the start of a cascade of enzyme activations resulting in processes like release of endocrine hormones and neurotransmitters, smooth muscle contraction, inflammation, ion transport and tumor promotion. The eventual products are effectors like ion channels, all kinds of enzymes, contractile proteins and transport proteins. Increased calcium levels can also directly activate other kinases and effectors.