Transient receptor potential protein subunit assembly and membrane distribution in human platelets

Brownlow, Sharon; Sage, Stewart O.

doi:10.1160/th05-06-0391

Cited by 94 publications

(70 citation statements)

References 44 publications

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“…S4) that rTRPV1 is primarily located in cholesterol-poor DSMs (thought to be related to non-raft microdomains) is similar to results for TRPC3 and TRPC6 (49), but in contrast to other TRP channels, such as TRPC1, TRPC4, and TRPC5 (49) and TRPM8 (42), that have been associated with cholesterol-rich DRMs. Although the reasons for these different microdomain locations are not clear, the different locations can impact on the TRP channels' response to cholesterol.…”

Section: Discussionsupporting

confidence: 63%

Identification of a Binding Motif in the S5 Helix That Confers Cholesterol Sensitivity to the TRPV1 Ion Channel

Picazo-Juárez

Romero-Suárez

Nieto-Posadas

et al. 2011

Journal of Biological Chemistry

123

113

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The TRPV1 ion channel serves as an integrator of noxious stimuli with its activation linked to pain and neurogenic inflammation. Cholesterol, a major component of cell membranes, modifies the function of several types of ion channels. Here, using measurements of capsaicin-activated currents in excised patches from TRPV1-expressing HEK cells, we show that enrichment with cholesterol, but not its diastereoisomer epicholesterol, markedly decreased wild-type rat TRPV1 currents. Substitutions in the S5 helix, rTRPV1-R579D, and rTRPV1-F582Q, decreased this cholesterol response and rTRPV1-L585I was insensitive to cholesterol addition. Two human TRPV1 variants, with different amino acids at position 585, had different responses to cholesterol with hTRPV1-Ile 585 being insensitive to this molecule. However, hTRPV1-I585L was inhibited by cholesterol addition similar to rTRPV1 with the same S5 sequence. In the absence of capsaicin, cholesterol enrichment also inhibited TRPV1 currents induced by elevated temperature and voltage. These data suggest that there is a cholesterol-binding site in TRPV1 and that the functions of TRPV1 depend on the genetic variant and membrane cholesterol content. The transient receptor potential (TRP)3 family of ion channels is found throughout the animal kingdom and has been shown to subserve numerous functions. One extensively studied member of this family is the TRPV1 (Vanilloid 1) channel. Structurally, TRPV1 is thought to be a tetramer comprised of subunits each with six transmembrane domains (S1-S6), with the putative pore of the channel located between S5 and S6. It also contains large intracellular amino and carboxyl termini that have been shown to be involved both in channel gating and regulation (for review, see Ref.

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Section: Discussionsupporting

confidence: 63%

Identification of a Binding Motif in the S5 Helix That Confers Cholesterol Sensitivity to the TRPV1 Ion Channel

Picazo-Juárez

Romero-Suárez

Nieto-Posadas

et al. 2011

Journal of Biological Chemistry

123

113

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“…Because other components, such as TRPC subunits, have been suggested to form part of the CCE apparatus, it is conceivable that another component may be limiting in the HEK293 cells used in this study. Previous work has suggested the localization of TRPC1, TRPC3, TRPC4, and TRPC5 in lipid raft domains (Ambudkar et al, 2004;Brownlow and Sage, 2005;Ambudkar, 2006). The localization of TPRC1 in these rafts seems to be essential for its role in store-mediated Ca 2ϩ entry, which was confirmed using caveolin knock-out mice (Murata et al, 1995).…”

Section: Camentioning

confidence: 67%

Capacitative Ca²⁺Entry via Orai1 and Stromal Interacting Molecule 1 (STIM1) Regulates Adenylyl Cyclase Type 8

Martin¹,

Willoughby²,

Ciruela³

et al. 2009

Mol Pharmacol

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Capacitative Ca 2ϩ entry (CCE), which occurs through the plasma membrane as a result of Ca 2ϩ store depletion, is mediated by stromal interacting molecule 1 (STIM1), a sensor of intracellular Ca 2ϩ store content, and the pore-forming component Orai1. However, additional factors, such as C-type transient receptor potential (TRPC) channels, may also participate in the CCE apparatus. To explore whether the store-dependent Ca 2ϩ entry reconstituted by coexpression of Orai1 and STIM1 has the functional properties of CCE, we used the Ca 2ϩ -calmodulin stimulated adenylyl cyclase type 8 (AC8), which responds selectively to CCE, whereas other modes of Ca 2ϩ entry, including those activated by arachidonate and the ionophore ionomycin, are ineffective. In addition, the Ca 2ϩ entry mediated by previous CCE candidates, diacylglycerol-activated TRPC channels, does not activate AC8.Here, we expressed Orai1 and STIM1 in HEK293 cells and saw a robust increment in CCE, and a proportional increase in CCEstimulated AC8 activity. Inhibitors of the CCE assembly process ablated the effects on cyclase activity in both AC8-overexpressing HEK293 cells and insulin-secreting MIN6 cells endogenously expressing Ca 2ϩ -sensitive AC isoforms. AC8 is believed to be closely associated with the source of CCE; indeed, not only were AC8, Orai1, and STIM1 colocalized at the plasma membrane but also all three proteins occurred in lipid rafts. Together, our data indicate that Orai1 and STIM1 can be integral components of the cAMP and CCE microdomain associated with adenylyl cyclase type 8.

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“…The experiments conformed to the guidelines stated in the Declaration of Helsinki. Platelet-rich plasma prepared as previously described [20].…”

Section: Platelet Preparationmentioning

confidence: 99%

“…In addition, thrombin releases Ca 2+ from acidic organelles via the formation of nicotinic acid adenine dinucleotide phosphate (NAADP) [4,20].…”

Section: Introductionmentioning

confidence: 99%

Conventional protein kinase C isoforms differentially regulate ADP- and thrombin-evoked Ca2+ signalling in human platelets

et al. 2015

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Rises in cytosolic Ca 2+ concentration ([Ca 2+ ] cyt ) are central in platelet activation, yet many aspects of the underlying mechanisms are poorly understood. Most studies examine how experimental manipulations affect agonist-evoked rises in [Ca 2+ ] cyt , but these only monitor the net effect of manipulations on the processes controlling [Ca 2+ ] cyt (Ca 2+ buffering, sequestration, release, entry and removal), and cannot resolve the source of the Ca 2+ or the transporters or channels affected. To investigate the effects of protein kinase C (PKC) on platelet Ca 2+ signalling, we here monitor Ca 2+ flux around the platelet by measuring net Ca 2+ fluxes to or from the extracellular space and the intracellular Ca 2+ stores, which act as the major sources and sinks for Ca 2+ influx into and efflux from the cytosol, as well as monitoring the cytosolic Na + concentration ([Na + ] cyt ), which influences platelet Ca 2+ fluxes via Na + /Ca 2+ exchange. The intracellular store Ca 2+ concentration ([Ca 2+ ] st ) was monitored using Fluo-5N, the extracellular Ca 2+ concentration ([Ca 2+ ] ext ) was monitored using Fluo-4 whilst [Ca 2+ ] cyt and [Na + ] cyt were monitored using Fura-2 and SFBI respectively. PKC inhibition using Ro-31-8220 or bisindolaemide I potentiated ADP-and thrombin-evoked rises in [Ca 2+ ] cyt in the absence of extracellular Ca 2+ . PKC inhibition potentiated ADP-evoked but reduced thrombin-evoked intracellular Ca 2+ release and Ca 2+ removal into the extracellular medium. SERCA inhibition using thapsigargin and 2,5-di(tert-butyl) l,4-benzohydroquinone abolished the effect of PKC inhibitors on ADP-evoked changes in [Ca 2+ ] cyt but only reduced the effect on thrombin-evoked responses. Thrombin evokes substantial rises in [Na + ] cyt which would be expected to reduce Ca 2+ removal via the Na + /Ca 2+ exchanger (NCX). Thrombinevoked rises in [Na + ] cyt were potentiated by PKC inhibition, an effect which was not due to altered changes in non-selective cation permeability of the plasma membrane as assessed by Mn 2+ quench of Fura-2 fluorescence. PKC inhibition was without effect on thrombin-evoked rises in [Ca 2+ ] cyt following SERCA inhibition and either removal of extracellular Na + or inhibition of Na + /K + -ATPase activity by removal of extracellular K + or treatment with digoxin. These data suggest that PKC limits ADP-evoked rises in [Ca 2+ ] cyt by acceleration of SERCA activity, whilst rises in [Ca 2+ ] cyt evoked by the stronger platelet activator thrombin are limited by PKC through acceleration of both SERCA and Na + /K + -ATPase activity, with the latter limiting the effect of thrombin on rises in [Na + ] cyt and so forward mode NCX activity. The use of selective PKC inhibitors indicated that conventional and not novel PKC isoforms are responsible for the inhibition of agonist-evoked Ca 2+ signalling.

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Transient receptor potential protein subunit assembly and membrane distribution in human platelets

Cited by 94 publications

References 44 publications

Identification of a Binding Motif in the S5 Helix That Confers Cholesterol Sensitivity to the TRPV1 Ion Channel

Identification of a Binding Motif in the S5 Helix That Confers Cholesterol Sensitivity to the TRPV1 Ion Channel

Capacitative Ca²⁺Entry via Orai1 and Stromal Interacting Molecule 1 (STIM1) Regulates Adenylyl Cyclase Type 8

Conventional protein kinase C isoforms differentially regulate ADP- and thrombin-evoked Ca2+ signalling in human platelets

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Transient receptor potential protein subunit assembly and membrane distribution in human platelets

Cited by 94 publications

References 44 publications

Identification of a Binding Motif in the S5 Helix That Confers Cholesterol Sensitivity to the TRPV1 Ion Channel

Identification of a Binding Motif in the S5 Helix That Confers Cholesterol Sensitivity to the TRPV1 Ion Channel

Capacitative Ca2+Entry via Orai1 and Stromal Interacting Molecule 1 (STIM1) Regulates Adenylyl Cyclase Type 8

Conventional protein kinase C isoforms differentially regulate ADP- and thrombin-evoked Ca2+ signalling in human platelets

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Capacitative Ca²⁺Entry via Orai1 and Stromal Interacting Molecule 1 (STIM1) Regulates Adenylyl Cyclase Type 8