The Drosophila trp (transient retinal potential) and trpl (trp-like) genes encode plasma membrane cation channels. Trp appears to encode a channel that allows calcium influx in non-excitable cells in response to
depletion of intracellular calcium pools (store-operated calcium entry), perhaps in association with the trpl gene
product, as part of the phototransduction process. Wes et al. (1995) isolated TRPC1, a homolog of trp, from a human
fetal brain cDNA library. TRPC1 showed 38 to 40% amino acid identity with Drosophila trp and trpl. Northern blot
analysis revealed that the predicted 810-amino acid protein is transcribed as a 5.4-kb mRNA at high levels in human
fetal and adult brain, in adult heart, testes, and ovary, and at lower levels in fetal liver and kidney.
General function
Channel/transport protein
Comment
Cellular localization
Plasma membrane
Comment
Ovarian function
Oogenesis
Comment
Expression regulated by
Comment
Ovarian localization
Oocyte
Comment
Zoltn Machty et al investigated the presence of the capacitative Ca2+ entry mechanism was investigated in porcine oocytes. In vitro-matured oocytes were treated with thapsigargin in Ca2+-free medium for 3 h to deplete intracellular calcium stores. After restoring extracellular
calcium, a large calcium influx was measured by using the calcium indicator dye fura-2, indicating capacitative Ca2+ entry.
A similar divalent cation influx could also be detected with the Mn2+-quench technique after inositol
1,4,5-triphosphate-induced Ca2+ release. In both cases, lanthanum, the Ca2+ permeable channel inhibitor, completely
blocked the influx caused by store depletion. Heterologous expression of Drosophila trp (transient receptor potential ) in porcine oocytes enhanced the
thapsigargin-induced Ca2+ influx. Polymerase chain reaction cloning using primers that were designed based on mouse and
human trp sequences revealed that porcine oocytes contain a trp homologue. As in other cell types, the capacitative Ca2+
entry mechanism might help in refilling the intracellular stores after the release of Ca2+ from the stores.