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TRPP2 and TRPV4 form a polymodal sensory channel complex.

Köttgen M, Buchholz B, Garcia-Gonzalez MA, Kotsis F, Fu X, Doerken M, Boehlke C, Steffl D, Tauber R, Wegierski T, Nitschke R, Suzuki M, Kramer-Zucker A, Germino GG, Watnick T, Prenen J, Nilius B, Kuehn EW, Walz G - J. Cell Biol. (2008)

Bottom Line: We find here that TRPP2 utilizes TRPV4 to form a mechano- and thermosensitive molecular sensor in the cilium.Depletion of TRPV4 in renal epithelial cells abolishes flow-induced calcium transients, demonstrating that TRPV4, like TRPP2, is an essential component of the ciliary mechanosensor.Because TRPV4-deficient zebrafish and mice lack renal cysts, our findings challenge the concept that defective ciliary flow sensing constitutes the fundamental mechanism of cystogenesis.

View Article: PubMed Central - PubMed

Affiliation: Renal Division, University Hospital Freiburg, 79106 Freiburg, Germany.

ABSTRACT
The primary cilium has evolved as a multifunctional cellular compartment that decorates most vertebrate cells. Cilia sense mechanical stimuli in various organs, but the molecular mechanisms that convert the deflection of cilia into intracellular calcium transients have remained elusive. Polycystin-2 (TRPP2), an ion channel mutated in polycystic kidney disease, is required for cilia-mediated calcium transients but lacks mechanosensitive properties. We find here that TRPP2 utilizes TRPV4 to form a mechano- and thermosensitive molecular sensor in the cilium. Depletion of TRPV4 in renal epithelial cells abolishes flow-induced calcium transients, demonstrating that TRPV4, like TRPP2, is an essential component of the ciliary mechanosensor. Because TRPV4-deficient zebrafish and mice lack renal cysts, our findings challenge the concept that defective ciliary flow sensing constitutes the fundamental mechanism of cystogenesis.

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TRPP2 and TRPV4 form a thermosensory complex in vitro and in vivo. (A) Analysis of TRP channel whole-cell currents under voltage clamp (Vc) conditions. Currents were recorded in X. laevis oocytes injected with cRNA encoding TRPP2 and/or TRPV4. Representative inward currents at 20°C or 39°C are shown. (B) Summary of data acquired in A. Asterisks indicate significant differences in the temperature-activated whole cell conductance (ΔG) compared with water-injected control oocytes; §, significant differences between data as indicated (n = 4, 4, 4, and 6, respectively). (C) Current-voltage (I–V) relations for oocytes expressing TRPV4 or TRPV4 and TRPP2 (D; gray: 20°C; black: 39°C). (E) Tail withdrawal latencies after immersion into a water bath at moderately hot temperatures were measured in mice of the indicated genotypes (n = 10 per genotype; asterisk indicates significant difference compared with wild-type [WT] and TRPV4+/− mice; §, significant difference from TRPP2+/− mice). (F) Tail withdrawal latencies at noxiously hot temperatures (n = 10 per genotype). Error bars represent mean values ± SEM.
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fig5: TRPP2 and TRPV4 form a thermosensory complex in vitro and in vivo. (A) Analysis of TRP channel whole-cell currents under voltage clamp (Vc) conditions. Currents were recorded in X. laevis oocytes injected with cRNA encoding TRPP2 and/or TRPV4. Representative inward currents at 20°C or 39°C are shown. (B) Summary of data acquired in A. Asterisks indicate significant differences in the temperature-activated whole cell conductance (ΔG) compared with water-injected control oocytes; §, significant differences between data as indicated (n = 4, 4, 4, and 6, respectively). (C) Current-voltage (I–V) relations for oocytes expressing TRPV4 or TRPV4 and TRPP2 (D; gray: 20°C; black: 39°C). (E) Tail withdrawal latencies after immersion into a water bath at moderately hot temperatures were measured in mice of the indicated genotypes (n = 10 per genotype; asterisk indicates significant difference compared with wild-type [WT] and TRPV4+/− mice; §, significant difference from TRPP2+/− mice). (F) Tail withdrawal latencies at noxiously hot temperatures (n = 10 per genotype). Error bars represent mean values ± SEM.

Mentions: Given the lack of epistasis between TRPP2 and TRPV4 in the zebrafish pronephros model, we chose another approach to investigate whether TRPP2 and TRPV4 form a sensory complex in vivo. TRPV4 is activated by warm temperature in addition to osmotic stress (Guler et al., 2002; Watanabe et al., 2002). TRPV4-deficient mice exhibit reduced responses to noxious stimuli and inflammation-induced thermal hyperalgesia (Liedtke and Friedman, 2003; Mizuno et al., 2003; Suzuki et al., 2003; Todaka et al., 2004), as well as a defective avoidance behavior at temperatures between 45 and 46°C, but a normal thermosensation profile at temperatures ≥47°C (Lee et al., 2005). To test whether TRPV4 and TRPP2 form a complex that is activated by warm temperatures, we expressed both proteins in X. laevis oocytes. The activation of TRPV4 by warm temperatures (39°C) was doubled in the presence of TRPP2 (Fig. 5, A–D), which is consistent with the hypothesis that the TRPV4–TRPP2 channel complex exerts a thermosensory function. Using a tail immersion assay, we detected that TRPP2+/− mice display a thermosensation profile that closely resembles the abnormalities described for TRPV4−/− mice (Fig. 5, E and F). Latencies in the tail immersion assay were significantly increased at 44°C and 46°C in TRPP2+/− mice (Fig. 5 E) but were comparable to wild-type mice at higher temperatures (Fig. 5 F). No differences were detected between wild-type and TRPV4+/− mice; however, the additional loss of one TRPP2 allele (transheterozygous animals) drastically augmented the thermosensory defect at 44°C and 46°C, exceeding the latencies for either TRPV4−/− or TRPP2+/− mice (Fig. 5, E and F). These findings provide clear genetic evidence that TRPV4 and TRPP2 collectively mediate thermosensation at moderately warm temperatures in the mouse. Our findings demonstrate that TRPP2 and TRPV4 jointly mediate thermosensation at moderate temperatures. Recent observations strongly support the concept that basal body and ciliary proteins play a role in temperature sensation, providing a link between the subcellular localization and function of the ion channels studied here (Tan et al., 2007).


TRPP2 and TRPV4 form a polymodal sensory channel complex.

Köttgen M, Buchholz B, Garcia-Gonzalez MA, Kotsis F, Fu X, Doerken M, Boehlke C, Steffl D, Tauber R, Wegierski T, Nitschke R, Suzuki M, Kramer-Zucker A, Germino GG, Watnick T, Prenen J, Nilius B, Kuehn EW, Walz G - J. Cell Biol. (2008)

TRPP2 and TRPV4 form a thermosensory complex in vitro and in vivo. (A) Analysis of TRP channel whole-cell currents under voltage clamp (Vc) conditions. Currents were recorded in X. laevis oocytes injected with cRNA encoding TRPP2 and/or TRPV4. Representative inward currents at 20°C or 39°C are shown. (B) Summary of data acquired in A. Asterisks indicate significant differences in the temperature-activated whole cell conductance (ΔG) compared with water-injected control oocytes; §, significant differences between data as indicated (n = 4, 4, 4, and 6, respectively). (C) Current-voltage (I–V) relations for oocytes expressing TRPV4 or TRPV4 and TRPP2 (D; gray: 20°C; black: 39°C). (E) Tail withdrawal latencies after immersion into a water bath at moderately hot temperatures were measured in mice of the indicated genotypes (n = 10 per genotype; asterisk indicates significant difference compared with wild-type [WT] and TRPV4+/− mice; §, significant difference from TRPP2+/− mice). (F) Tail withdrawal latencies at noxiously hot temperatures (n = 10 per genotype). Error bars represent mean values ± SEM.
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fig5: TRPP2 and TRPV4 form a thermosensory complex in vitro and in vivo. (A) Analysis of TRP channel whole-cell currents under voltage clamp (Vc) conditions. Currents were recorded in X. laevis oocytes injected with cRNA encoding TRPP2 and/or TRPV4. Representative inward currents at 20°C or 39°C are shown. (B) Summary of data acquired in A. Asterisks indicate significant differences in the temperature-activated whole cell conductance (ΔG) compared with water-injected control oocytes; §, significant differences between data as indicated (n = 4, 4, 4, and 6, respectively). (C) Current-voltage (I–V) relations for oocytes expressing TRPV4 or TRPV4 and TRPP2 (D; gray: 20°C; black: 39°C). (E) Tail withdrawal latencies after immersion into a water bath at moderately hot temperatures were measured in mice of the indicated genotypes (n = 10 per genotype; asterisk indicates significant difference compared with wild-type [WT] and TRPV4+/− mice; §, significant difference from TRPP2+/− mice). (F) Tail withdrawal latencies at noxiously hot temperatures (n = 10 per genotype). Error bars represent mean values ± SEM.
Mentions: Given the lack of epistasis between TRPP2 and TRPV4 in the zebrafish pronephros model, we chose another approach to investigate whether TRPP2 and TRPV4 form a sensory complex in vivo. TRPV4 is activated by warm temperature in addition to osmotic stress (Guler et al., 2002; Watanabe et al., 2002). TRPV4-deficient mice exhibit reduced responses to noxious stimuli and inflammation-induced thermal hyperalgesia (Liedtke and Friedman, 2003; Mizuno et al., 2003; Suzuki et al., 2003; Todaka et al., 2004), as well as a defective avoidance behavior at temperatures between 45 and 46°C, but a normal thermosensation profile at temperatures ≥47°C (Lee et al., 2005). To test whether TRPV4 and TRPP2 form a complex that is activated by warm temperatures, we expressed both proteins in X. laevis oocytes. The activation of TRPV4 by warm temperatures (39°C) was doubled in the presence of TRPP2 (Fig. 5, A–D), which is consistent with the hypothesis that the TRPV4–TRPP2 channel complex exerts a thermosensory function. Using a tail immersion assay, we detected that TRPP2+/− mice display a thermosensation profile that closely resembles the abnormalities described for TRPV4−/− mice (Fig. 5, E and F). Latencies in the tail immersion assay were significantly increased at 44°C and 46°C in TRPP2+/− mice (Fig. 5 E) but were comparable to wild-type mice at higher temperatures (Fig. 5 F). No differences were detected between wild-type and TRPV4+/− mice; however, the additional loss of one TRPP2 allele (transheterozygous animals) drastically augmented the thermosensory defect at 44°C and 46°C, exceeding the latencies for either TRPV4−/− or TRPP2+/− mice (Fig. 5, E and F). These findings provide clear genetic evidence that TRPV4 and TRPP2 collectively mediate thermosensation at moderately warm temperatures in the mouse. Our findings demonstrate that TRPP2 and TRPV4 jointly mediate thermosensation at moderate temperatures. Recent observations strongly support the concept that basal body and ciliary proteins play a role in temperature sensation, providing a link between the subcellular localization and function of the ion channels studied here (Tan et al., 2007).

Bottom Line: We find here that TRPP2 utilizes TRPV4 to form a mechano- and thermosensitive molecular sensor in the cilium.Depletion of TRPV4 in renal epithelial cells abolishes flow-induced calcium transients, demonstrating that TRPV4, like TRPP2, is an essential component of the ciliary mechanosensor.Because TRPV4-deficient zebrafish and mice lack renal cysts, our findings challenge the concept that defective ciliary flow sensing constitutes the fundamental mechanism of cystogenesis.

View Article: PubMed Central - PubMed

Affiliation: Renal Division, University Hospital Freiburg, 79106 Freiburg, Germany.

ABSTRACT
The primary cilium has evolved as a multifunctional cellular compartment that decorates most vertebrate cells. Cilia sense mechanical stimuli in various organs, but the molecular mechanisms that convert the deflection of cilia into intracellular calcium transients have remained elusive. Polycystin-2 (TRPP2), an ion channel mutated in polycystic kidney disease, is required for cilia-mediated calcium transients but lacks mechanosensitive properties. We find here that TRPP2 utilizes TRPV4 to form a mechano- and thermosensitive molecular sensor in the cilium. Depletion of TRPV4 in renal epithelial cells abolishes flow-induced calcium transients, demonstrating that TRPV4, like TRPP2, is an essential component of the ciliary mechanosensor. Because TRPV4-deficient zebrafish and mice lack renal cysts, our findings challenge the concept that defective ciliary flow sensing constitutes the fundamental mechanism of cystogenesis.

Show MeSH
Related in: MedlinePlus