Endogenously Expressed Trp1 Is Involved in Store-mediated Ca2+ Entry by Conformational Coupling in Human Platelets

• Published in: The Journal of biological chemistry 2002-11, Vol.277 (44), p.42157-42163
• Main Authors: Rosado, Juan A, Brownlow, Sharon L, Sage, Stewart O
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Blood Platelets - metabolism; Calcium - metabolism; Calcium Channels - metabolism; Calcium Channels - physiology; Epitope Mapping; Humans; Inositol 1,4,5-Trisphosphate Receptors; Manganese - metabolism; Molecular Sequence Data; Protein Conformation; Receptors, Cytoplasmic and Nuclear - metabolism; Thapsigargin - pharmacology; Thrombin - pharmacology; TRPC Cation Channels
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M207320200

Physical interaction between transient receptor potential (Trp) channels and inositol 1,4,5-trisphosphate receptors (IP 3 Rs) has been presented as a candidate mechanism for the activation of store-mediated Ca 2+ entry. The role of a human homologue of Drosophila transient receptor potential channel, hTrp1, in the conduction of store-mediated Ca 2+ entry was examined in human platelets. Incubation of platelets with a specific antibody, which recognizes the extracellular amino acid sequence 557–571 of hTrp1, inhibited both store depletion-induced Ca 2+ and Mn 2+ entry in a concentration-dependent manner. Stimulation of platelets with the physiological agonist thrombin activated coupling between the IP 3 receptor type II and endogenously expressed hTrp1. This event was reversed by refilling of the internal Ca 2+ stores but maintained after removal of the agonist if the stores were not allowed to refill. Inhibition of IP 3 recycling using Li + or inhibition of IP 3 Rs with xestospongin C or treatment with jasplakinolide, to stabilize the cortical actin filament network, abolished thrombin-induced coupling between hTrp1 and IP 3 R type II. Incubation with the anti-hTrp1 antibody inhibited thrombin-evoked Ca 2+ entry without affecting Ca 2+ release from intracellular stores. These results provide evidence for the involvement of hTrp1 in the activation of store-mediated Ca 2+ entry by coupling to IP 3 R type II in normal human cells.