transmembrane signaling receptor activity GO:0004888 This term includes intracellular membrane receptors, e.g. IP3 triggered release of Ca2+ from intracellular stores. molecular_function GO:0099600 GO:0004926 Reactome:R-HSA-193672 Combining with an extracellular or intracellular signal and transmitting the signal from one side of the membrane to the other to initiate a change in cell activity or state as part of signal transduction. transmembrane receptor activity transmembrane signalling receptor activity signaling receptor activity