Activation of recombinant trp by thapsigargin in Sf9 insect cells

• Published in: The American journal of physiology Vol. 267; no. 5; pp. C1501 - C1505
• Main Authors: Vaca, L, Sinkins, W.G, Hu, Y, Kunze, D.L, Schilling, W.P
• Format: Journal Article
• Language: English
• Published: United States 01.11.1994
• Subjects: Animals; Baculoviridae; Baculoviridae - genetics; calcium; Calcium - metabolism; Calcium Channels - physiology; calcium ion channels; calcium pump inhibitors; Calcium-Transporting ATPases - antagonists & inhibitors; Cell Line; cell lines; cell membranes; DNA, Complementary; Drosophila; Drosophila Proteins; Electrophysiology; gene expression; Genetic Vectors; inhibitors; inorganic ions; Insect Hormones - genetics; Insect Hormones - metabolism; Insect Proteins; Insecta - cytology; ion exchange capacity; Membrane Proteins - genetics; Membrane Proteins - metabolism; proteins; Receptors, Bradykinin - genetics; recombinant DNA; Recombinant Proteins; Recombination, Genetic; Spodoptera frugiperda; Terpenes - pharmacology; Thapsigargin; Transient Receptor Potential Channels; Virus Diseases - physiopathology
• ISSN: 0002-9513; 2163-5773
• DOI: 10.1152/ajpcell.1994.267.5.c1501

The mammalian protein responsible for Ca2+ release-activated current (Icrac) may be homologous to the Drosophila protein designated trp. Thus the activity of trp, and another Drosophila protein designated trp-like or trpl, may be linked to depletion of the internal Ca2+ store via the so-called capacitative Ca2+ entry mechanism. To test this hypothesis, the effect of thapsigargin, a selective inhibitor of the endoplasmic reticulum Ca2+ pump, on trp- and trpl-induced whole cell membrane current was determined using the baculovirus Sf9 insect cell expression system. The results demonstrate that trp and trpl form Ca2+-permeable cation channels. The trpl encodes a nonselective cation channel that is constitutively active under basal nonstimulated conditions and is unaffected by thapsigargin, whereas trp is more selective for Ca2+ than Na+ and is activated by depletion of the internal Ca2+ store. Although evaluation of cation selectivity suggests that trp is not identical to the channel responsible for Icrac, these channels must share some structural feature(s) since both are activated by thapsigargin. A unique proline-rich region in the COOH-terminal tail of trp, which is absent in trpl, may be necessary for capacitative Ca2+ entry.