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Drosophila TRPM channel is essential for the control of extracellular magnesium levels.

Hofmann T, Chubanov V, Chen X, Dietz AS, Gudermann T, Montell C - PLoS ONE (2010)

Bottom Line: We generated mutations in trpm and found that this resulted in shortening of the Malpighian tubules.In contrast to all other Drosophila trp mutations, loss of trpm was essential for viability, as trpm mutations resulted in pupal lethality.Feeding high Mg2+ also resulted in elevated Mg2+ in the hemolymph, but had relatively little effect on cellular Mg2+.

View Article: PubMed Central - PubMed

Affiliation: Institut für Pharmakologie und Toxikologie, Philipps-Universität Marburg, Marburg, Germany.

ABSTRACT
The TRPM group of cation channels plays diverse roles ranging from sensory signaling to Mg2+ homeostasis. In most metazoan organisms the TRPM subfamily is comprised of multiple members, including eight in humans. However, the Drosophila TRPM subfamily is unusual in that it consists of a single member. Currently, the functional requirements for this channel have not been reported. Here, we found that the Drosophila TRPM protein was expressed in the fly counterpart of mammalian kidneys, the Malpighian tubules, which function in the removal of electrolytes and toxic components from the hemolymph. We generated mutations in trpm and found that this resulted in shortening of the Malpighian tubules. In contrast to all other Drosophila trp mutations, loss of trpm was essential for viability, as trpm mutations resulted in pupal lethality. Supplementation of the diet with a high concentration of Mg2+ exacerbated the phenotype, resulting in growth arrest during the larval period. Feeding high Mg2+ also resulted in elevated Mg2+ in the hemolymph, but had relatively little effect on cellular Mg2+. We conclude that loss of Drosophila trpm leads to hypermagnesemia due to a defect in removal of Mg2+ from the hemolymph. These data provide the first evidence for a role for a Drosophila TRP channel in Mg2+ homeostasis, and underscore a broad and evolutionarily conserved role for TRPM channels in Mg2+ homeostasis.

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Related in: MedlinePlus

Expression of trpm in Malpighian tubules.(A) Detection of trpm RNA in Malpighian tubules of stage 16–17 embryos by in situ hybridization. Arrows indicate the localization of the anterior and posterior Malpighian tubules in the left panel using the antisense probe. (B) Malpighian tubules from w1118 3rd instar larvae stained with TRPM antibodies. (C) Malpighian tubules from trpm1 3rd instar larvae stained with TRPM antibodies. Abbreviations: ms = main segment, ts = transitional segment, is =  initial segment, I = type 1/principal cell, II =  type 2/stellate/bar-shaped cell. The stainings of the epithelial apical (ap) and basolateral compartments are indicated.
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pone-0010519-g005: Expression of trpm in Malpighian tubules.(A) Detection of trpm RNA in Malpighian tubules of stage 16–17 embryos by in situ hybridization. Arrows indicate the localization of the anterior and posterior Malpighian tubules in the left panel using the antisense probe. (B) Malpighian tubules from w1118 3rd instar larvae stained with TRPM antibodies. (C) Malpighian tubules from trpm1 3rd instar larvae stained with TRPM antibodies. Abbreviations: ms = main segment, ts = transitional segment, is =  initial segment, I = type 1/principal cell, II =  type 2/stellate/bar-shaped cell. The stainings of the epithelial apical (ap) and basolateral compartments are indicated.

Mentions: To determine whether trpm was expressed in Malpighian tubules, we examined the expression pattern of the RNAs and proteins. To characterize the spatial distribution of the trpm RNA, we performed in situ hybridizations using late stage embryos. We found that the trpm signal labeled the Malpighian tubules most prominently (Figure 5A). While some signal appeared in variable regions of the embryo with the sense control, in contrast to the anti-sense probe, the control did not label any specific region consistently and never stained the Malpighian tubules.


Drosophila TRPM channel is essential for the control of extracellular magnesium levels.

Hofmann T, Chubanov V, Chen X, Dietz AS, Gudermann T, Montell C - PLoS ONE (2010)

Expression of trpm in Malpighian tubules.(A) Detection of trpm RNA in Malpighian tubules of stage 16–17 embryos by in situ hybridization. Arrows indicate the localization of the anterior and posterior Malpighian tubules in the left panel using the antisense probe. (B) Malpighian tubules from w1118 3rd instar larvae stained with TRPM antibodies. (C) Malpighian tubules from trpm1 3rd instar larvae stained with TRPM antibodies. Abbreviations: ms = main segment, ts = transitional segment, is =  initial segment, I = type 1/principal cell, II =  type 2/stellate/bar-shaped cell. The stainings of the epithelial apical (ap) and basolateral compartments are indicated.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2865541&req=5

pone-0010519-g005: Expression of trpm in Malpighian tubules.(A) Detection of trpm RNA in Malpighian tubules of stage 16–17 embryos by in situ hybridization. Arrows indicate the localization of the anterior and posterior Malpighian tubules in the left panel using the antisense probe. (B) Malpighian tubules from w1118 3rd instar larvae stained with TRPM antibodies. (C) Malpighian tubules from trpm1 3rd instar larvae stained with TRPM antibodies. Abbreviations: ms = main segment, ts = transitional segment, is =  initial segment, I = type 1/principal cell, II =  type 2/stellate/bar-shaped cell. The stainings of the epithelial apical (ap) and basolateral compartments are indicated.
Mentions: To determine whether trpm was expressed in Malpighian tubules, we examined the expression pattern of the RNAs and proteins. To characterize the spatial distribution of the trpm RNA, we performed in situ hybridizations using late stage embryos. We found that the trpm signal labeled the Malpighian tubules most prominently (Figure 5A). While some signal appeared in variable regions of the embryo with the sense control, in contrast to the anti-sense probe, the control did not label any specific region consistently and never stained the Malpighian tubules.

Bottom Line: We generated mutations in trpm and found that this resulted in shortening of the Malpighian tubules.In contrast to all other Drosophila trp mutations, loss of trpm was essential for viability, as trpm mutations resulted in pupal lethality.Feeding high Mg2+ also resulted in elevated Mg2+ in the hemolymph, but had relatively little effect on cellular Mg2+.

View Article: PubMed Central - PubMed

Affiliation: Institut für Pharmakologie und Toxikologie, Philipps-Universität Marburg, Marburg, Germany.

ABSTRACT
The TRPM group of cation channels plays diverse roles ranging from sensory signaling to Mg2+ homeostasis. In most metazoan organisms the TRPM subfamily is comprised of multiple members, including eight in humans. However, the Drosophila TRPM subfamily is unusual in that it consists of a single member. Currently, the functional requirements for this channel have not been reported. Here, we found that the Drosophila TRPM protein was expressed in the fly counterpart of mammalian kidneys, the Malpighian tubules, which function in the removal of electrolytes and toxic components from the hemolymph. We generated mutations in trpm and found that this resulted in shortening of the Malpighian tubules. In contrast to all other Drosophila trp mutations, loss of trpm was essential for viability, as trpm mutations resulted in pupal lethality. Supplementation of the diet with a high concentration of Mg2+ exacerbated the phenotype, resulting in growth arrest during the larval period. Feeding high Mg2+ also resulted in elevated Mg2+ in the hemolymph, but had relatively little effect on cellular Mg2+. We conclude that loss of Drosophila trpm leads to hypermagnesemia due to a defect in removal of Mg2+ from the hemolymph. These data provide the first evidence for a role for a Drosophila TRP channel in Mg2+ homeostasis, and underscore a broad and evolutionarily conserved role for TRPM channels in Mg2+ homeostasis.

Show MeSH
Related in: MedlinePlus