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Light-regulated interaction of Dmoesin with TRP and TRPL channels is required for maintenance of photoreceptors.

Chorna-Ornan I, Tzarfaty V, Ankri-Eliahoo G, Joel-Almagor T, Meyer NE, Huber A, Payre F, Minke B - J. Cell Biol. (2005)

Bottom Line: Furthermore, we show that light-activated migration of Dmoesin results from the dephosphorylation of a conserved threonine in Dmoesin.The expression of a Dmoesin mutant form that impairs this phosphorylation inhibits Dmoesin movement and leads to light-induced retinal degeneration.Thus, our data strongly suggest that the light- and phosphorylation-dependent dynamic association of Dmoesin to membrane channels is involved in maintenance of the photoreceptor cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.

ABSTRACT
Recent studies in Drosophila melanogaster retina indicate that absorption of light causes the translocation of signaling molecules and actin from the photoreceptor's signaling membrane to the cytosol, but the underlying mechanisms are not fully understood. As ezrin-radixin-moesin (ERM) proteins are known to regulate actin-membrane interactions in a signal-dependent manner, we analyzed the role of Dmoesin, the unique D. melanogaster ERM, in response to light. We report that the illumination of dark-raised flies triggers the dissociation of Dmoesin from the light-sensitive transient receptor potential (TRP) and TRP-like channels, followed by the migration of Dmoesin from the membrane to the cytoplasm. Furthermore, we show that light-activated migration of Dmoesin results from the dephosphorylation of a conserved threonine in Dmoesin. The expression of a Dmoesin mutant form that impairs this phosphorylation inhibits Dmoesin movement and leads to light-induced retinal degeneration. Thus, our data strongly suggest that the light- and phosphorylation-dependent dynamic association of Dmoesin to membrane channels is involved in maintenance of the photoreceptor cells.

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Protein blot showing light-dependent movement of Dmoesin from the membrane to the cytosol. (A) Membrane-associated (pellet) and soluble (sup) protein fractions were separated by high-speed centrifugation and processed for Western blotting with αDmoesin antibodies. Head extracts were prepared from dark-raised (Dark) or illuminated (Light) flies of the following genotypes: WT, trp P343 (trp), and norpA P24 (norpA). Although illumination induces redistribution of Dmoesin from membranes to the cytosol in WT flies, inactivation of either TRP or NORPA blocks the light-dependent movement of Dmoesin. (B) The histogram plots Dmoesin levels in the pellet divided by the total amount of Dmoesin present in extracts from WT, trp, and norpA heads, as revealed from repeated experiments done in similar conditions to those in A. P < 0.01; n = 5. The error bars are SEM.
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fig1: Protein blot showing light-dependent movement of Dmoesin from the membrane to the cytosol. (A) Membrane-associated (pellet) and soluble (sup) protein fractions were separated by high-speed centrifugation and processed for Western blotting with αDmoesin antibodies. Head extracts were prepared from dark-raised (Dark) or illuminated (Light) flies of the following genotypes: WT, trp P343 (trp), and norpA P24 (norpA). Although illumination induces redistribution of Dmoesin from membranes to the cytosol in WT flies, inactivation of either TRP or NORPA blocks the light-dependent movement of Dmoesin. (B) The histogram plots Dmoesin levels in the pellet divided by the total amount of Dmoesin present in extracts from WT, trp, and norpA heads, as revealed from repeated experiments done in similar conditions to those in A. P < 0.01; n = 5. The error bars are SEM.

Mentions: To test this possibility, we examined the distribution of Dmoesin between the membrane and cytosolic fractions in head extracts of dark-raised and illuminated D. melanogaster. Although Dmoesin was detected in both the soluble and membrane fractions, the majority of Dmoesin was associated with the membrane fraction in dark-raised flies (Fig. 1 A). In contrast, Dmoesin was predominantly in the soluble fraction in illuminated WT flies (Fig. 1 A). Quantification of the Dmoesin membrane/cytosolic ratio further supports the conclusion that illumination induces a substantial movement of Dmoesin from the membrane to the soluble fraction (Fig. 1 B). Upon illumination, nearly 50% of the membrane-associated Dmoesin of the head moved to the cytosol. By using mutants lacking eyes (Fig. S1, available online at http://www.jcb.org/cgi/content/full/jcb.200503014/DC1) we found that the Dmoesin protein present in heads, outside the photoreceptors, remained associated with membranes upon illumination and therefore was not affected by light.


Light-regulated interaction of Dmoesin with TRP and TRPL channels is required for maintenance of photoreceptors.

Chorna-Ornan I, Tzarfaty V, Ankri-Eliahoo G, Joel-Almagor T, Meyer NE, Huber A, Payre F, Minke B - J. Cell Biol. (2005)

Protein blot showing light-dependent movement of Dmoesin from the membrane to the cytosol. (A) Membrane-associated (pellet) and soluble (sup) protein fractions were separated by high-speed centrifugation and processed for Western blotting with αDmoesin antibodies. Head extracts were prepared from dark-raised (Dark) or illuminated (Light) flies of the following genotypes: WT, trp P343 (trp), and norpA P24 (norpA). Although illumination induces redistribution of Dmoesin from membranes to the cytosol in WT flies, inactivation of either TRP or NORPA blocks the light-dependent movement of Dmoesin. (B) The histogram plots Dmoesin levels in the pellet divided by the total amount of Dmoesin present in extracts from WT, trp, and norpA heads, as revealed from repeated experiments done in similar conditions to those in A. P < 0.01; n = 5. The error bars are SEM.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1936436&req=5

fig1: Protein blot showing light-dependent movement of Dmoesin from the membrane to the cytosol. (A) Membrane-associated (pellet) and soluble (sup) protein fractions were separated by high-speed centrifugation and processed for Western blotting with αDmoesin antibodies. Head extracts were prepared from dark-raised (Dark) or illuminated (Light) flies of the following genotypes: WT, trp P343 (trp), and norpA P24 (norpA). Although illumination induces redistribution of Dmoesin from membranes to the cytosol in WT flies, inactivation of either TRP or NORPA blocks the light-dependent movement of Dmoesin. (B) The histogram plots Dmoesin levels in the pellet divided by the total amount of Dmoesin present in extracts from WT, trp, and norpA heads, as revealed from repeated experiments done in similar conditions to those in A. P < 0.01; n = 5. The error bars are SEM.
Mentions: To test this possibility, we examined the distribution of Dmoesin between the membrane and cytosolic fractions in head extracts of dark-raised and illuminated D. melanogaster. Although Dmoesin was detected in both the soluble and membrane fractions, the majority of Dmoesin was associated with the membrane fraction in dark-raised flies (Fig. 1 A). In contrast, Dmoesin was predominantly in the soluble fraction in illuminated WT flies (Fig. 1 A). Quantification of the Dmoesin membrane/cytosolic ratio further supports the conclusion that illumination induces a substantial movement of Dmoesin from the membrane to the soluble fraction (Fig. 1 B). Upon illumination, nearly 50% of the membrane-associated Dmoesin of the head moved to the cytosol. By using mutants lacking eyes (Fig. S1, available online at http://www.jcb.org/cgi/content/full/jcb.200503014/DC1) we found that the Dmoesin protein present in heads, outside the photoreceptors, remained associated with membranes upon illumination and therefore was not affected by light.

Bottom Line: Furthermore, we show that light-activated migration of Dmoesin results from the dephosphorylation of a conserved threonine in Dmoesin.The expression of a Dmoesin mutant form that impairs this phosphorylation inhibits Dmoesin movement and leads to light-induced retinal degeneration.Thus, our data strongly suggest that the light- and phosphorylation-dependent dynamic association of Dmoesin to membrane channels is involved in maintenance of the photoreceptor cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.

ABSTRACT
Recent studies in Drosophila melanogaster retina indicate that absorption of light causes the translocation of signaling molecules and actin from the photoreceptor's signaling membrane to the cytosol, but the underlying mechanisms are not fully understood. As ezrin-radixin-moesin (ERM) proteins are known to regulate actin-membrane interactions in a signal-dependent manner, we analyzed the role of Dmoesin, the unique D. melanogaster ERM, in response to light. We report that the illumination of dark-raised flies triggers the dissociation of Dmoesin from the light-sensitive transient receptor potential (TRP) and TRP-like channels, followed by the migration of Dmoesin from the membrane to the cytoplasm. Furthermore, we show that light-activated migration of Dmoesin results from the dephosphorylation of a conserved threonine in Dmoesin. The expression of a Dmoesin mutant form that impairs this phosphorylation inhibits Dmoesin movement and leads to light-induced retinal degeneration. Thus, our data strongly suggest that the light- and phosphorylation-dependent dynamic association of Dmoesin to membrane channels is involved in maintenance of the photoreceptor cells.

Show MeSH
Related in: MedlinePlus