Trp1, a candidate protein for the store-operated Ca2+ influx mechanism in salivary gland cells.

Liu, Xibao; Wang, Weiching; Singh, Brij B.; Lockwich, Timothy; Jadlowiec, Julie; O’Connell, Brian; Wellner, Robert B.; Zhu, Michael X.; Ambudkar, Indu S.

doi:10.1016/s0021-9258(18)30113-3

Cited by 13 publications

(9 citation statements)

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“…Yue et al (2001) suggested that CaT1 carries the I CRAC current, but Voets et al (2001) convincingly showed that CaT1 can be distinguished from I CRAC on the basis of sensitivity to store-depleting agents, inward recti¢cation in the absence of divalent cations, relative permeability to Na þ and Cs þ , e¡ect of 2-APB, and voltage-dependent channel gating by intracellular Mg 2 þ . Other reports suggest that TRPC4 or TRPC1 is the I CRAC channel (Liu et al, 2000;Philipp et al, 2000). Some TRP channels were recently shown to be expressed in keratinocytes (Clapham, 2002;Peier et al, 2002;Xu et al, 2002), so the above hypothesis is also applicable to keratinocytes; however, characteristics of other channels are sometime attributed to I CRAC channels (Prakriya and Lewis, 2002).…”

Section: Discussionmentioning

confidence: 98%

Sequential Activation of Store-Operated Currents In Human Gingival Keratinocytes

Fatherazi

Belton

Izutsu

2003

Journal of Investigative Dermatology

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Calcium ion store-activated currents in undifferentiated human gingival keratinocytes were measured with the whole cell patch clamp and fura techniques. Thapsigargin or intracellular inositol 1,4,5-trisphosphate and BAPTA rapidly induced an early transient current with I(CRAC) (calcium release activated calcium ion current) characteristics, and several later, larger sustained currents that depended on the mode of store depletion. Thapsigargin activated two currents within minutes of I(CRAC) activation. The first was a nonspecific cation current, I(NSC). A second conducted Na+ and Cs+, and was partially inhibited by thapsigargin (INa1). Dialysis with inositol 1,4,5-trisphosphate and BAPTA induced a later current that also conducted Na+ and Cs+, but was inhibited by extracellular calcium ion (INa2), with properties consistent with an epithelial Na+ channel current in some cells, and a calcium ion-insensitive Na+ current (INa3). Comparison of thapsigargin-evoked current changes with fura-2/AM results from separate cells indicated that both the I(CRAC) and the later, larger calcium ion conducting currents contributed to changes in intracellular calcium ion concentration, and likely play important parts in calcium ion signaling in undifferentiated keratinocytes.

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Section: Discussionmentioning

confidence: 98%

Sequential Activation of Store-Operated Currents In Human Gingival Keratinocytes

Fatherazi

Belton

Izutsu

2003

Journal of Investigative Dermatology

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“…This has been shown by heterologous expression of TRPC proteins. Using this methodology, TRPC1-5 have been shown to be possibly activated by store depletion (Groschner et al, 1998;Philipp et al, 1998;Vannier et al, 1999;Warnat et al, 1999;Liu et al, 2000). However, other authors showed that heterologous expression of TRPC3-6 also gave channels whose activation was independent of store depletion (Zitt et al, 1997;Hofmann et al, 1999;Schaefer et al, 2000;Wu et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

Involvement of TRPC in the abnormal calcium influx observed in dystrophic (mdx) mouse skeletal muscle fibers

Vandebrouck

Martin

Schoor

et al. 2002

The Journal of Cell Biology

309

306

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Duchenne muscular dystrophy results from the lack of dystrophin, a cytoskeletal protein associated with the inner surface membrane, in skeletal muscle. The absence of dystrophin induces an abnormal increase of sarcolemmal calcium influx through cationic channels in adult skeletal muscle fibers from dystrophic (mdx) mice. We observed that the activity of these channels was increased after depletion of the stores of calcium with thapsigargin or caffeine. By analogy with the situation observed in nonexcitable cells, we therefore hypothesized that these store-operated channels could belong to the transient receptor potential channel (TRPC) family. We measured the expression of TRPC isoforms in normal and mdx adult skeletal muscles fibers, and among the seven known isoforms, five were detected (TRPC1, 2, 3, 4, and 6) by RT-PCR. Western blot analysis and immunocytochemistry of normal and mdx muscle fibers demonstrated the localization of TRPC1, 4, and 6 proteins at the plasma membrane. Therefore, an antisense strategy was used to repress these TRPC isoforms. In parallel with the repression of the TRPCs, we observed that the occurrence of calcium leak channels was decreased to one tenth of its control value (patch-clamp technique), showing the involvement of TRPC in the abnormal calcium influx observed in dystrophic fibers.

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“…TRPC1 is considered to be a SOC candidate (Ambudkar, 2006). TRPC1 is endogenously expressed in HSG cells, and when stably overexpressed enhances SOC infl ux, unlike overexpression of TRPC3 (Liu et al, 2000). Why would depletion of TRPC1 have no effect on lacritin-induced Ca 2+ infl ux, NFATC1 translocation, or mitogenesis; or on SOC in the thapsigargin-treated cells of Roos et al (2005) and Liou et al (2005)?…”

Section: Discussionmentioning

confidence: 99%

“…When 100 μM 2-APB was added to lacritin-or thapsigargin-treated cells at maximal mobilization, suppression was immediate (unpublished data). TRPC channels (including TRPC1 in HSG cells; Liu et al, 2000) have been proposed to be essential for SOC. In two recent comprehensive and independent siRNA screens for SOC mediators, the major hits were to STIM1 and STIM2 (Roos et al, 2005;Liou et al, 2005).…”

Section: Distinctive Lacritin Mitogenic Signaling Through Pkc𝛂mentioning

confidence: 99%

Restricted epithelial proliferation by lacritin via PKCα-dependent NFAT and mTOR pathways

Wang

Xie

et al. 2006

The Journal of Cell Biology

124

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Renewal of nongermative epithelia is poorly understood. The novel mitogen “lacritin” is apically secreted by several nongermative epithelia. We tested 17 different cell types and discovered that lacritin is preferentially mitogenic or prosecretory for those types that normally contact lacritin during its glandular outward flow. Mitogenesis is dependent on lacritin's C-terminal domain, which can form an α-helix with a hydrophobic face, as per VEGF's and PTHLP's respective dimerization or receptor-binding domain. Lacritin targets downstream NFATC1 and mTOR. The use of inhibitors or siRNA suggests that lacritin mitogenic signaling involves Gαi or Gαo–PKCα-PLC–Ca2+–calcineurin–NFATC1 and Gαi or Gαo–PKCα-PLC–phospholipase D (PLD)–mTOR in a bell-shaped, dose-dependent manner requiring the Ca2+ sensor STIM1, but not TRPC1. This pathway suggests the placement of transiently dephosphorylated and perinuclear Golgi–translocated PKCα upstream of both Ca2+ mobilization and PLD activation in a complex with PLCγ2. Outward flow of lacritin from secretory cells through ducts may generate a proliferative/secretory field as a different unit of cellular renewal in nongermative epithelia where luminal structures predominate.

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Trp1, a candidate protein for the store-operated Ca2+ influx mechanism in salivary gland cells.

Cited by 13 publications

References 0 publications

Sequential Activation of Store-Operated Currents In Human Gingival Keratinocytes

Sequential Activation of Store-Operated Currents In Human Gingival Keratinocytes

Involvement of TRPC in the abnormal calcium influx observed in dystrophic (mdx) mouse skeletal muscle fibers

Restricted epithelial proliferation by lacritin via PKCα-dependent NFAT and mTOR pathways

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