An inositol 1,4,5-trisphosphate receptor-dependent cation entry pathway in DT40 B lymphocytes.
We examined the roles of inositol 1,4,5-trisphosphate (IP3) receptors (IP3R) in calcium signaling using DT40 B lymphocytes, and a variant lacking the three IP3R isoforms (IP3R-KO). In wild-type cells, B cell receptor (BCR) stimulation activates a cation entry route that exhibits significantly greater permeability to Ba2+ than does capacitative calcium entry. This cation entry is absent in IP3R-KO cells. Expression of the type-3 IP3R (IP3R-3) in the IP3R-KO cells rescued not only agonist-dependent release of intracellular Ca2+, but also Ba2+ influx following receptor stimulation. Similar results were obtained with an IP3R-3 mutant carrying a conservative point mutation in the selectivity filter region of the channel (D2477E); however, an IP3R-3 mutant in which this same aspartate was replaced by alanine (D2477A) failed to restore either BCR-induced Ca2+ release or receptor-dependent Ba2+ entry. These results suggest that in DT40 B lymphocytes, BCR stimulation activates a novel cation entry across the plasma membrane that depends upon, or is mediated by, fully functional IP3R.
Calcium Regulation Section, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences-NIH, PO Box 12233, 111 TW Alexander Drive, Research Triangle Park, NC 27709, USA.
Guillermo
G
Vazquez
Barbara J
BJ
Wedel
Gary St J
GS
Bird
Suresh K
SK
Joseph
James W
JW
Putney
D019943:Amino Acid Substitution; D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D001464:Barium / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D002645:Chickens; D053496:Inositol 1,4,5-Trisphosphate Receptors; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D020125:Mutation, Missense; D017354:Point Mutation; D020033:Protein Isoforms / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D051381:Rats; D011947:Receptors, Antigen, B-Cell / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000502:physiology; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D020033:Protein Isoforms; D011947:Receptors, Antigen, B-Cell; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D001464:Barium; D019284:Thapsigargin; D002118:Calcium