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A novel ion channel formed by interaction of TRPML3 with TRPV5.

Guo Z, Grimm C, Becker L, Ricci AJ, Heller S - PLoS ONE (2013)

Bottom Line: It has pharmacological similarity with TRPML3 and requires functional TRPML3 as well as functional TRPV5.Single channel analyses revealed that TRPML3 and TRPV5 heteromers have different features than the respective homomers, and furthermore, that they occur in potentially distinct stoichiometric configurations.Based on overlapping expression of TRPML3 and TRPV5 in the kidney and the inner ear, we propose that TRPML3 and TRPV5 heteromers could have a biological function in these organs.

View Article: PubMed Central - PubMed

Affiliation: Department of Otolaryngology-HNS, Stanford University School of Medicine, Palo Alto, California, United States of America.

ABSTRACT
TRPML3 and TRPV5 are members of the mucolipin (TRPML) and TRPV subfamilies of transient receptor potential (TRP) cation channels. Based on sequence similarities of the pore forming regions and on structure-function evidence, we hypothesized that the pore forming domains of TRPML and TRPV5/TRPV6 channels have similarities that indicate possible functional interactions between these TRP channel subfamilies. Here we show that TRPML3 and TRPV5 associate to form a novel heteromeric ion channel. This novel conductance is detectable under conditions that do not activate either TRPML3 or TRPV5. It has pharmacological similarity with TRPML3 and requires functional TRPML3 as well as functional TRPV5. Single channel analyses revealed that TRPML3 and TRPV5 heteromers have different features than the respective homomers, and furthermore, that they occur in potentially distinct stoichiometric configurations. Based on overlapping expression of TRPML3 and TRPV5 in the kidney and the inner ear, we propose that TRPML3 and TRPV5 heteromers could have a biological function in these organs.

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Pharmacological properties of HEK293 cells expressing TRPV5, TRPML3, and both proteins.(A–C) Representative traces shown from transfected HEK293 cells expressing TRPV5, TRPML3, and TRPV5/TRPML3 in response to step polarization (from 0 mV to –150 mV) before (black lines) and after 1 mM dihydrostreptomycin (DHSM) (green lines), 100 µM Ruthenium Red (RR) (cyan lines) and 300 µM gadolinium chloride (Gd3+) (purple lines). (D) Quantitative analysis of the percentage of inhibition at −150 mV (mean±SD, n = 4–8).
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pone-0058174-g003: Pharmacological properties of HEK293 cells expressing TRPV5, TRPML3, and both proteins.(A–C) Representative traces shown from transfected HEK293 cells expressing TRPV5, TRPML3, and TRPV5/TRPML3 in response to step polarization (from 0 mV to –150 mV) before (black lines) and after 1 mM dihydrostreptomycin (DHSM) (green lines), 100 µM Ruthenium Red (RR) (cyan lines) and 300 µM gadolinium chloride (Gd3+) (purple lines). (D) Quantitative analysis of the percentage of inhibition at −150 mV (mean±SD, n = 4–8).

Mentions: To characterize the novel conductance pharmacologically, various blockers were used. We employed the inner ear sensory hair cell mechanoelectrical transduction channel blocker dihydrostreptomycin (DHSM, [19], [20]), because TRPV and TRPML channels have been discussed as potential hair cell transduction channel candidates [21], [22]. DHSM, at 1 mM, did not block TRPV5, TRPML3, or the novel conductance (Fig. 3A,D). Ruthenium red is a potent blocker of TRPV5 [23], [24] and at 100 µM, the reagent abolished more than 90% of the TRPV5 current elicited at −150 mV (Fig. 3B,D). TRPML3-based currents were not affected by ruthenium red, nor was the novel conductance. Gadolinium ion, a non-specific cation channel blocker that affects many TRP channels as well as mechanosensitive channels [25], blocked more than 90% of TRPV5 currents and partially blocked TRPML3 (Fig. 3C,D, see also [1]). The novel conductance was also partially blocked by gadolinium ion. Based on these pharmacological assessments, we conclude that the novel conductance has no pharmacological resemblance with TRPV5, but for the blockers tested, it resembles TRPML3. Nevertheless, this result has to be interpreted with caution because no specific blockers, particularly for TRPML3 are available.


A novel ion channel formed by interaction of TRPML3 with TRPV5.

Guo Z, Grimm C, Becker L, Ricci AJ, Heller S - PLoS ONE (2013)

Pharmacological properties of HEK293 cells expressing TRPV5, TRPML3, and both proteins.(A–C) Representative traces shown from transfected HEK293 cells expressing TRPV5, TRPML3, and TRPV5/TRPML3 in response to step polarization (from 0 mV to –150 mV) before (black lines) and after 1 mM dihydrostreptomycin (DHSM) (green lines), 100 µM Ruthenium Red (RR) (cyan lines) and 300 µM gadolinium chloride (Gd3+) (purple lines). (D) Quantitative analysis of the percentage of inhibition at −150 mV (mean±SD, n = 4–8).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585263&req=5

pone-0058174-g003: Pharmacological properties of HEK293 cells expressing TRPV5, TRPML3, and both proteins.(A–C) Representative traces shown from transfected HEK293 cells expressing TRPV5, TRPML3, and TRPV5/TRPML3 in response to step polarization (from 0 mV to –150 mV) before (black lines) and after 1 mM dihydrostreptomycin (DHSM) (green lines), 100 µM Ruthenium Red (RR) (cyan lines) and 300 µM gadolinium chloride (Gd3+) (purple lines). (D) Quantitative analysis of the percentage of inhibition at −150 mV (mean±SD, n = 4–8).
Mentions: To characterize the novel conductance pharmacologically, various blockers were used. We employed the inner ear sensory hair cell mechanoelectrical transduction channel blocker dihydrostreptomycin (DHSM, [19], [20]), because TRPV and TRPML channels have been discussed as potential hair cell transduction channel candidates [21], [22]. DHSM, at 1 mM, did not block TRPV5, TRPML3, or the novel conductance (Fig. 3A,D). Ruthenium red is a potent blocker of TRPV5 [23], [24] and at 100 µM, the reagent abolished more than 90% of the TRPV5 current elicited at −150 mV (Fig. 3B,D). TRPML3-based currents were not affected by ruthenium red, nor was the novel conductance. Gadolinium ion, a non-specific cation channel blocker that affects many TRP channels as well as mechanosensitive channels [25], blocked more than 90% of TRPV5 currents and partially blocked TRPML3 (Fig. 3C,D, see also [1]). The novel conductance was also partially blocked by gadolinium ion. Based on these pharmacological assessments, we conclude that the novel conductance has no pharmacological resemblance with TRPV5, but for the blockers tested, it resembles TRPML3. Nevertheless, this result has to be interpreted with caution because no specific blockers, particularly for TRPML3 are available.

Bottom Line: It has pharmacological similarity with TRPML3 and requires functional TRPML3 as well as functional TRPV5.Single channel analyses revealed that TRPML3 and TRPV5 heteromers have different features than the respective homomers, and furthermore, that they occur in potentially distinct stoichiometric configurations.Based on overlapping expression of TRPML3 and TRPV5 in the kidney and the inner ear, we propose that TRPML3 and TRPV5 heteromers could have a biological function in these organs.

View Article: PubMed Central - PubMed

Affiliation: Department of Otolaryngology-HNS, Stanford University School of Medicine, Palo Alto, California, United States of America.

ABSTRACT
TRPML3 and TRPV5 are members of the mucolipin (TRPML) and TRPV subfamilies of transient receptor potential (TRP) cation channels. Based on sequence similarities of the pore forming regions and on structure-function evidence, we hypothesized that the pore forming domains of TRPML and TRPV5/TRPV6 channels have similarities that indicate possible functional interactions between these TRP channel subfamilies. Here we show that TRPML3 and TRPV5 associate to form a novel heteromeric ion channel. This novel conductance is detectable under conditions that do not activate either TRPML3 or TRPV5. It has pharmacological similarity with TRPML3 and requires functional TRPML3 as well as functional TRPV5. Single channel analyses revealed that TRPML3 and TRPV5 heteromers have different features than the respective homomers, and furthermore, that they occur in potentially distinct stoichiometric configurations. Based on overlapping expression of TRPML3 and TRPV5 in the kidney and the inner ear, we propose that TRPML3 and TRPV5 heteromers could have a biological function in these organs.

Show MeSH
Related in: MedlinePlus