Intracellular ADP modulates the Ca2+ release-activated Ca2+ current in a temperature- and Ca2+-dependent Way.
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.
Innocenti
B
B
Department of Biomedical Sciences, CNR Center for the Study of Biomembranes, University of Padova, Via Trieste 75, 35131 Padova, Italy.
Pozzan
T
T
Fasolato
C
C
D000227:Adenine Nucleotides / Q000737:chemistry; D000244:Adenosine Diphosphate / Q000737:chemistry*; D000818:Animals; D001491:Basophils; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology*; D002460:Cell Line; D006150:Guanine Nucleotides / Q000737:chemistry; D015640:Ion Channel Gating; D018408:Patch-Clamp Techniques; D051381:Rats; D013696:Temperature
D000227:Adenine Nucleotides; D015220:Calcium Channels; D006150:Guanine Nucleotides; D000244:Adenosine Diphosphate; D002118:Calcium