Novel Ca2+ channels underlying transduction in Drosophila photoreceptors: implications for phosphoinositide-mediated Ca2+ mobilization

Hardie, Roger C.; Minke, Baruch

doi:10.1016/0166-2236(93)90095-4

Cited by 242 publications

(153 citation statements)

References 50 publications

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“…trp, trpl, or Htrp-1, are yet to be found across different species. Indeed, although the two Drosophila trp proteins are most related among the four, the functional roles of trp and trpl in Drosophila phototransduction are thought to be different [6,20]. When expressed in Sf9 cells, the Drosophila trp was activated by store depletion whereas the Drosophila trpl was not and channels formed by these two proteins also had different ion selectivities [10,11].…”

Section: Discussionmentioning

confidence: 99%

“…The insect phototransduction pathway is mediated through the activation of PLC coupled by a Gq type protein [6]. The consequent generation of IP3 and the release of Ca 2+ from its intracellular storage pools is believed to lead to the opening of a light sensitive ion channel and generation of a depolarizing receptor potential.…”

Section: ~ Introductionmentioning

confidence: 99%

“…Similar to intracellular Ca 2+ changes in mammalian cells following stimulation by agonists acting via PLC, electroretinograms of Drosophila eyes are biphasic with an initial peak followed by a sustained phase of which the latter is dependent on extracellular Ca 2+. This sustained phase is absent in the trp mutant which was therefore proposed to be caused by a defect in the Ca 2+ influx pathway [6]. The trp gene was cloned [7,8].…”

Section: ~ Introductionmentioning

confidence: 99%

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Molecular cloning of a widely expressed human homologue for the Drosophila trp gene

et al. 1995

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The Drosophila transient receptor potential (trp) gene and its homologue, trpl, have been suggested to mediate calcium entry during the insect's phototransduction process. We isolated human cDNA, human trp-1 (Htrp-1), encoding a polypeptide .f 793 amino acids that is 37% identical (62% similar) to Drosophila trp and trpl. Northern analysis showed that the Htrp-1 transcript is approximately 5.5 kb and expressed in most human tissues, with higher amounts in ovary, testis, heart, and brain.Isolation of Htrp-I suggests that a trp-type protein is present in mammals and should provide a useful tool in studying calciumdepletion induced calcium influx processes.:~ey words': Transient receptor potential; Calcium influx , hannel; Ca 2+ signaling ~. IntroductionCalcium regulation plays an important role in many cellular 0rocesses. In non-excitable mammalian cells, activation of i~hosphoinositide-specific phospholipase C (PLC) produces ~nositol 1,4,5-trisphosphate (IP3), which in turn causes the reease of intracellular calcium from its storage pools in the endo~lasmic reticulum. This results in a transient elevation of cyosolic-free Ca 2+, which is normally followed by a Ca 2+ influx 'rom the extracellular space. By refilling the pools, Ca 2+ influx )lays an important role in prolonging the Ca 2+ signal, allowing or localized signaling, and maintaining Ca 2÷ oscillations [1].Calcium influx in non-excitable cells is thought to occur hrough plasma membrane channels which, in contrast to the voltage-dependent Ca 2+ channels in excitable cells, are operated lot by changes of membrane potentials but rather by how full he internal Ca 2+ stores are [2]. Although studies using either luorescent Ca 2+ indicators or electrophysiological techniques lave suggested that multiple types of Ca 2+ permeant channels nay be involved in different cell types to fulfill the influx funcion, the molecular structure of the channels and the mechalism that regulates the influx have remained unclear and reprerent one of the major unanswered questions of cellular Ca -,+ !lomeostasis [3][4][5].Candidates involved in voltage-independent Ca 2+ entry into [9]. A detailed analysis of the trpl sequence showed that it shares moderate homology with voltage-dependent Ca 2+ and Na ÷ channels at their putative transmembrane regions. However, in clear contrast with the voltage-dependent channels, it lacks the positively charged amino acid residues at the presumed $4 segment which are thought to act as voltage sensors that promote gating in response to changes in membrane potentials. The structural homology to Ca 2+ and Na + channels together with the absence of charged residues in trpl and trp suggested that these proteins may form voltage-independent ion channels. This was demonstrated recently by expression of the cDNAs for trp and trpl in insect Sf9 cells using the baculovirus system. It was fount that trp forms a Ca 2÷ permeable cation channel which is activated by store depletion with thapsigargin [10] whereas trpl forms a Ca -'+ permeable non-selec...

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Section: Discussionmentioning

confidence: 99%

Section: ~ Introductionmentioning

confidence: 99%

Section: ~ Introductionmentioning

confidence: 99%

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Molecular cloning of a widely expressed human homologue for the Drosophila trp gene

et al. 1995

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“…Whole-fly electroretinography as well as voltage-clamp experiments with individual photoreceptors using both wild-type and mutants strongly suggested that these gene products are key cation (Ca"?) channels in the generation of reception potential during phototransduction in the fly [20,21].…”

Section: Trp and Trpl Of Drosophilamentioning

confidence: 99%

Ion channel regulation by calmodulin binding

Saimi

Kung

1994

FEBS Letters

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While many ion channels are modulated by phosphorylation, there is growing evidence that they can also be regulated by Ca*'calmodulin, apparently through direct binding. In some cases, this binding activates channels; in others, it modulates channel activities. These phenomena have been documented in Paramecium, in Drosophila, in vertebrate photoreceptors and olfactory receptors, as well as in ryanodine receptor Ca*'-release channels. Furthermore, studies on calmodulin mutants in Paramecium have shown a clear bipartite distribution of two groups of mutations in the calmodulin gene that lead to opposite behavioral and electrophysiological phenotypes. These results indicate that the N-lobe of calmodulin specifically interacts with one class of ion-channel proteins and the C-lobe with another.

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“…The members of the C (for canonical) family of TRP (transient receptor potential)-related ion channels (TRPCs) have been postulated as candidates for forming both ROCE and capacitative Ca 2ϩ entry channels (8)(9)(10). There are seven TRPC family members (C1-C7; reviewed in ref.…”

mentioning

confidence: 99%

Orai proteins interact with TRPC channels and confer responsiveness to store depletion

Liao¹,

Erxleben

Yildirim³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

277

232

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The TRPC (C-type transient receptor potential) class of ion channels has been hypothesized to participate in store-operated Ca 2؉ entry (SOCE). Recently, however, STIM1 and Orai1 proteins have been proposed to form SOCE channels. Whether TRPCs participate in SOCE that is dependent on or regulated by Orai has not been explored. Here we show that Orai1 physically interacts with the N and C termini of TRPC3 and TRPC6, and that in cells overexpressing either TRPC3 or TRPC6 in a store-depletion insensitive manner, these TRPCs become sensitive to store depletion upon expression of an exogenous Orai. Thus, Orai-1, -2, and -3 enhanced thapsigargin-induced calcium entry by 50 -150% in cells stably overexpressing either TRPC3 or TRPC6. Orai1 expression had no significant effect on endogenous, thapsigargin-induced calcium entry in wildtype cells (HEK-293, COS1), in HEK cells expressing a thapsigarginsensitive variant of TRPC3 (TRPC3a), or in HEK cells overexpressing another membrane protein, V1aR. Single-channel cation currents present in membrane patches of TRPC3-overexpressing cells were suppressed by expression of Orai1. We propose that Orai proteins by interacting with TRPCs act as regulatory subunits that confer STIM1-mediated store depletion sensitivity to these channels.capacitative calcium entry ͉ ion channels ͉ thapsigargin ͉ transmembrane signaling

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Novel Ca2+ channels underlying transduction in Drosophila photoreceptors: implications for phosphoinositide-mediated Ca2+ mobilization

Cited by 242 publications

References 50 publications

Molecular cloning of a widely expressed human homologue for the Drosophila trp gene

Molecular cloning of a widely expressed human homologue for the Drosophila trp gene

Ion channel regulation by calmodulin binding

Orai proteins interact with TRPC channels and confer responsiveness to store depletion

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