Plasma membrane IP3 receptors.
IP3Rs (inositol 1,4,5-trisphosphate receptors) are expressed in the membranes of non-mitochondrial organelles in most animal cells, but their presence and role within the plasma membrane are unclear. Whole-cell patch-clamp recording from DT40 cells expressing native or mutated IP3Rs has established that each cell expresses just two or three functional IP3Rs in its plasma membrane. Only approx. 50% of the Ca2+ entry evoked by stimulation of the B-cell receptor is mediated by store-operated Ca2+ entry, the remainder appears to be carried by the IP3Rs expressed in the plasma membrane. Ca2+ entering the cell via just two large-conductance IP3Rs is likely to have very different functional consequences from the comparable amount of Ca2+ that enters through the several thousand low-conductance store-operated channels.
Taylor
C W
CW
Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK. cwt1000@cam.ac.uk
Dellis
O
O
D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology; D001692:Biological Transport; D002118:Calcium / Q000502:physiology; D002462:Cell Membrane / Q000502:physiology*; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000502:physiology*; D015388:Organelles / Q000502:physiology*
D053496:Inositol 1,4,5-Trisphosphate Receptors; D002118:Calcium