Inositol 1,4,5-trisphosphate and its co-players in the concert of Ca2+ signalling--new faces in the line up.
Release of Ca2+ from intracellular stores can occur by different intracellular messengers such as InsP3, cADPR and NAADP. Although in some cells messengers may operate on different stores, there are also Ca2+ stores with sensitivities for all three of these messengers. It is well documented, that InsP3- and cADPR-sensitive Ca2+ stores are involved in the activation of "store-operated Ca2+ channels" (SOCC). It has not yet been unequivocally shown, however, if Ca2+ release from stores, which respond to NAADP but not to InsP3 or cADPR, also generate signals which lead to "store-operated Ca2+ entry". Neither localization nor the mechanism of coupling to the plasma membrane of those InsP3- and cADPR-sensitive Ca2+ stores which activate SOCCs is yet clear. In this review localization and properties of InsP3-, cADPR- and NAADP-sensitive Ca2+ pools and their mutual interactions are discussed. Differential sensitivities of Ca2+ release mechanisms to InsP3, cADPR and NAADP have consequences on Ca2+ release, Ca2+ oscillations, propagation of Ca2+ waves and on activation of SOCC. Possible interaction of InsP3R and cADPR with candidates of SOCCs (TRP channels) and mechanisms involved in the regulation of SOCCs (activation-deactivation) will be elaborated.
Schulz
Irene
I
Institute of Physiology, 66421 Homburg/Saar, Germany. irene.schulz@uniklinik-saarland.de
Krause
Elmar
E
D020013:Calcium Signaling; D036563:Cyclic ADP-Ribose / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D009249:NADP / Q000031:analogs & derivatives / Q000378:metabolism
D036563:Cyclic ADP-Ribose; D009249:NADP; C024376:NAADP; D015544:Inositol 1,4,5-Trisphosphate