An inositol 1,4,5-trisphosphate receptor-dependent cation entry pathway in DT40 B lymphocytes

• Published in: The EMBO journal Vol. 21; no. 17; pp. 4531 - 4538
• Main Authors: Vazquez, Guillermo, Wedel, Barbara J., Bird, Gary St J., Joseph, Suresh K., Putney Jr, James W.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 02-09-2002; Blackwell Publishing Ltd; Oxford University Press
• Subjects: Amino Acid Substitution; Animals; B lymphocyte; B-Lymphocytes - drug effects; B-Lymphocytes - metabolism; Barium - metabolism; Calcium; Calcium - metabolism; calcium channels; Calcium Channels - deficiency; Calcium Channels - genetics; Calcium Channels - physiology; Calcium Signaling - drug effects; Calcium Signaling - physiology; Cell Line; Chickens; Inositol 1,4,5-Trisphosphate Receptors; inositol trisphosphate receptor; Ion Channel Gating - drug effects; Ion Channel Gating - physiology; Lymphocytes; Mutation, Missense; phospholipase C; plasma membrane; Point Mutation; Protein Isoforms - deficiency; Protein Isoforms - genetics; Protein Isoforms - physiology; Rats; Receptors, Antigen, B-Cell - physiology; Receptors, Cytoplasmic and Nuclear - deficiency; Receptors, Cytoplasmic and Nuclear - genetics; Receptors, Cytoplasmic and Nuclear - physiology; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - physiology; Thapsigargin - pharmacology; Transfection
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1093/emboj/cdf467

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.