Late stage results from the probe development effort to identify selective agonists of the Transient Receptor Potential Channels 3 (TRPML3): Fura-2 profiling assay
Name: Late stage results from the probe development effort to identify selective agonists of the Transient Receptor Potential Channels 3 (TRPML3): Fura-2 profiling assay. ..more
BioActive Compounds: 3
Source (MLPCN Center Name): The Scripps Research Institute Molecular Screening Center (SRIMSC)
Center Affiliation: The Scripps Research Institute (TSRI)
Assay Provider: Stefan Heller, Stanford University
Network: Molecular Libraries Probe Production Centers Network (MLPCN)
Grant Proposal Number: 1 R03 MH083077-01
Grant Proposal PI: Stefan Heller, Stanford University
External Assay ID: TRPML3_AG_FURA-2 LATE STAGE
Name: Late stage results from the probe development effort to identify selective agonists of the Transient Receptor Potential Channels 3 (TRPML3): Fura-2 profiling assay.
Cell signaling pathways that mediate osmosensation, photosensation, and thermosensation depend on a family of diverse transient receptor potential (TRP) cation channels, which are activated by agonist-receptor coupling (1-5). A role for these channels in inner ear hair cell mechanotransduction was gleaned from TRP channel mutations identified in flies, worms, and lower vertebrates with defective balance and impaired sensitivity to touch (1-5). TRPML3 (mucolipin 3; MCOLN3) is a TRP channel expressed in inner ear hair cells and stereocilia (5-7), suggesting it may play a role in hearing and mechanotransduction. Reports that mice with mutations in TRPML3 (known as varitint-waddler mutants) exhibit early-onset hearing loss accompanied by head-bobbing and circling behaviors (8-10), provide further support for a role of TRPML3 in hearing and vestibular function. As a result, the identification of selective probes for TRPML3 would be useful to investigate the function of TRPML3 in inner ear mechanotransduction and hearing biology (11).
1. Clapham, D.E., TRP channels as cellular sensors. Nature. 2003. 426(6966): p. 517-24.
2. Cuajungco, M.P., C. Grimm, and S. Heller, TRP channels as candidates for hearing and balance abnormalities in vertebrates. Biochim Biophys Acta. 2007. 1772(8): p. 1022-7.
3. Gillespie, P.G. and R.G. Walker. Molecular basis of mechanosensory transduction. Nature. 2001. 413(6852): p. 194-202.
4. Eberl, D.F., R.W. Hardy, and M.J. Kernan. Genetically similar transduction mechanisms for touch and hearing in Drosophila. J Neurosci. 2000. 20(16): p. 5981-8.
5. Gong, Z., W. Son, Y.D. Chung, J. Kim, D.W. Shin, C.A. McClung, Y. Lee, H.W. Lee, D.J. Chang, B.K. Kaang, H. Cho, U. Oh, J. Hirsh, M.J. Kernan, and C. Kim. Two interdependent TRPV channel subunits, inactive and Nanchung, mediate hearing in Drosophila. J Neurosci. 2004. 24(41): p. 9059-66.
6. Kim, J., Y.D. Chung, D.Y. Park, S. Choi, D.W. Shin, H. Soh, H.W. Lee, W. Son, J. Yim, C.S. Park, M.J. Kernan, and C. Kim. A TRPV family ion channel required for hearing in Drosophila. Nature. 2003. 424(6944): p. 81-4.
7. Walker, R.G., A.T. Willingham, and C.S. Zuker. A Drosophila mechanosensory transduction channel. Science. 2000. 287(5461): p. 2229-34.
8. Corey, D.P. What is the hair cell transduction channel? J Physiol. 2006. 576(Pt 1): p. 23-8.
9. Shin, J.B., D. Adams, M. Paukert, M. Siba, S. Sidi, M. Levin, P.G. Gillespie, and S. Grunder. Xenopus TRPN1 (NOMPC) localizes to microtubule-based cilia in epithelial cells, including inner-ear hair cells. Proc Natl Acad Sci U S A. 2005. 102(35): p. 12572-7.
10. Sidi, S., R.W. Friedrich, and T. Nicolson. NompC TRP channel required for vertebrate sensory hair cell mechanotransduction. Science. 2003. 301(5629): p. 96-9.
11. Small molecule activators of TRPML3. Grimm C, Jors S, Saldanha SA, Obukhov AG, Pan B, Oshima K, Cuajungco MP, Chase P, Hodder P, Heller S. Chem Biol. 2010 Feb 26;17(2):135-148.
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The purpose of these assays is to determine whether compounds identified as probe candidates are able to increase whole cell Ca2+ influx in HEK293 cells transfected with human TRPML3, other human, or murine (m) TRP channels, or zebrafish TRPN1. In this assay cells transiently expressing channels or YFP control plasmid are perfused with test compound, followed by measurement of intracellular [Ca2+] for 2 minutes with the fluorescent indicator fura-2-AM. Fura-2-AM is the membrane-permeable derivative of Fura-2. Compounds are added to cells 20-25 hours after transfection. Values are reported as mean values +/- SEM (n ≥ 3 independent experiments with 20-30 cells). The % activation values for TRPML2 in the SAR tables were calculated by normalizing the TRPML2 response ratios to TRPML3 response ratios. Compounds are tested at 10 micromolar. Please see reference 11 for details.
This assay measures increases of intracellular calcium in TRPML3-transfected cells using fura-2 as the calcium indicator dye. Measurements of [Ca2+]i with the fluorescent indicators fura-2-AM was performed using a monochromator-based imaging system (iMIC platform and Polychrome V monochromator, TILL Photonics). HEK293 cells, plated onto glass coverslips, were loaded with 4 micromolar fura-2-AM in a standard bath solution (SBS) containing 138 mM NaCl, 6 mM KCl, 2 mM MgCl2, 2 mM CaCl2, 10 mM HEPES, and 5.5 mM d-glucose (adjusted to pH 7.4 with NaOH) (11).
PubChem Activity Outcome and Score:
In this assay the PubChem Activity Score is assigned a value of 100 for probe compounds, 50 for actives and 0 for inactives. There are no inactive compounds.
List of Reagents:
TRPML3 HEK293 cell line (provided by Prof. Stefan Heller)
** Test Concentration.
Data Table (Concise)