* Ligand-gated ion channels such as the nicotinic acetylcholine receptor and GABAA receptor are composed of five subunits arranged around a central pore that opens to allow ions to pass through. There are many different subunits available that can come together in a wide variety of combinations to form different subtypes of the ion channel. Sometimes the channel can be made from only one type of subunit, such as the α7 nicotinic receptor, which is made up from five α7 subunits, and so is a homomer rather than a<unk> , but more commonly several different types of subunit will come together to form a<unk> ic complex (e.g., the α4β2 nicotinic receptor, which is made up from two α4 subunits and three β2 subunits). Because the different ion channel subtypes are expressed to different extents in different tissues, this allows selective modulation of ion transport and means that a single neurotransmitter can produce varying effects depending on where in the body it is released. * G protein-coupled receptors are composed of seven membrane-spanning alpha-helical segments that are usually linked together into a single folded chain to form the receptor complex. However, research has demonstrated that a number of GPCRs are also capable of forming<unk> s from a combination of two or more individual GPCR subunits under some circumstances, especially where several different GPCRs are densely expressed in the same neuron. Such<unk> s may be between receptors from the same family (e.g., adenosine A1/A2A<unk> s and dopamine D1/D2 and D1/D3<unk> s) or between entirely unrelated receptors such as CB1/A2A, glutamate mGluR5 / adenosine A2A<unk> s, cannabinoid CB1 / dopamine D2<unk> s, and even CB1/A2A/D2 heterotrimers where three different receptors have come together to form a<unk> . The ligand binding properties and intracellular trafficking pathways of GPCR<unk> s usually show elements from both parent receptors, but may also produce quite unexpected pharmacological effects, making such<unk> s an important focus of current research.
Heteromer
Abionic
Heterologous
Sense
Tocolytic
Clone 
Proximate
Highmark