Innocenti B, Pozzan T, Fasolato C
Department of Biomedical Sciences, CNR Center for the Study of Biomembranes, University of Padova, Via Trieste 75, 35131 Padova, Italy.
J Biol Chem. 1996 Apr 12;271(15):8582-7. doi: 10.1074/jbc.271.15.8582.
The rat basophilic cell line RBL-1 is known to express high levels of the Ca2+ current activated by store depletion, known as Ca2+ release-activated Ca2+ current (ICRAC), the main Ca2+ influx pathway so far identified in nonexcitable cells. We show here that, as reported in other cell types, metabolic drugs strongly inhibit the Ca2+ influx operated by store depletion in RBL-1 cells also. We have tested the hypothesis that intracellular adenine and/or guanine nucleotide levels act as coupling factors between ICRAC and cell metabolism. Using the whole cell configuration of the patch-clamp technique, we demonstrate that addition of ADP to the intracellular solution significantly reduces ICRAC induced by inositol 1,4,5-trisphosphate. This phenomenon differs from other regulatory pathways of ICRAC, since it is highly temperature-dependent, is observable only in the presence of low intracellular Ca2+ buffering capacity, and requires a cytosolic factor(s) which is rapidly lost during cell dialysis. Moreover, the inhibition is specific for ADP and is partially mimicked by ADPbetaS and AMP, but not by GDP or GTP.
