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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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The light-dependent movement of Dmoesin from the membrane to the cytosol is blocked in the Dmoesin-T559A and Dmoesin-T559D mutants. (A) Western blot analysis of Dmoesin distribution in membrane-bound or -soluble fractions of D. melanogaster head protein extracts. Membrane and soluble proteins extracted from dark-raised and illuminated Dmoesin-GFP transgenic lines were Western blotted using αGFP. Extracts were prepared from the same fly strains as Fig. 7, as indicated. (B) The histogram plots the ratio of membrane-bound to total Dmoesin signals from replicate experiments similar to that shown in A. Although illumination halves levels of WT Dmoesin in association with membranes (P < 0.01; n = 3), no significant modification of Dmoesin distribution is provoked by illumination of Dmoesin-T559A-GFP and Dmoesin-T559D-GFP. The error bars are SEM.
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fig8: The light-dependent movement of Dmoesin from the membrane to the cytosol is blocked in the Dmoesin-T559A and Dmoesin-T559D mutants. (A) Western blot analysis of Dmoesin distribution in membrane-bound or -soluble fractions of D. melanogaster head protein extracts. Membrane and soluble proteins extracted from dark-raised and illuminated Dmoesin-GFP transgenic lines were Western blotted using αGFP. Extracts were prepared from the same fly strains as Fig. 7, as indicated. (B) The histogram plots the ratio of membrane-bound to total Dmoesin signals from replicate experiments similar to that shown in A. Although illumination halves levels of WT Dmoesin in association with membranes (P < 0.01; n = 3), no significant modification of Dmoesin distribution is provoked by illumination of Dmoesin-T559A-GFP and Dmoesin-T559D-GFP. The error bars are SEM.

Mentions: To support this interpretation using a different approach, we analyzed the impact of T559 mutations on Dmoesin movement through biochemical characterization. The membrane and soluble fractions of head extracts from flies expressing Dmoesin-WT-GFP, Dmoesin-T559A-GFP, and Dmoesin-T559D-GFP were fractionated by SDS-PAGE and analyzed by Western blots using anti-GFP antibodies (Fig. 8 A). Although illumination reduced the Dmoesin level in the membrane fraction and concomitantly increased Dmoesin levels in the cytosol of Dmoesin-WT-GFP, the distribution of phosphorylation-defective Dmoesin mutants was unmodified by light (Fig. 8, A and B). As expected, the major fraction of Dmoesin-T559A-GFP was restricted to the soluble fraction, whereas the Dmoesin-T559D-GFP appeared in both the membrane-associated and the cytosol fractions (Fig. 8).


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)

The light-dependent movement of Dmoesin from the membrane to the cytosol is blocked in the Dmoesin-T559A and Dmoesin-T559D mutants. (A) Western blot analysis of Dmoesin distribution in membrane-bound or -soluble fractions of D. melanogaster head protein extracts. Membrane and soluble proteins extracted from dark-raised and illuminated Dmoesin-GFP transgenic lines were Western blotted using αGFP. Extracts were prepared from the same fly strains as Fig. 7, as indicated. (B) The histogram plots the ratio of membrane-bound to total Dmoesin signals from replicate experiments similar to that shown in A. Although illumination halves levels of WT Dmoesin in association with membranes (P < 0.01; n = 3), no significant modification of Dmoesin distribution is provoked by illumination of Dmoesin-T559A-GFP and Dmoesin-T559D-GFP. The error bars are SEM.
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Related In: Results  -  Collection

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

fig8: The light-dependent movement of Dmoesin from the membrane to the cytosol is blocked in the Dmoesin-T559A and Dmoesin-T559D mutants. (A) Western blot analysis of Dmoesin distribution in membrane-bound or -soluble fractions of D. melanogaster head protein extracts. Membrane and soluble proteins extracted from dark-raised and illuminated Dmoesin-GFP transgenic lines were Western blotted using αGFP. Extracts were prepared from the same fly strains as Fig. 7, as indicated. (B) The histogram plots the ratio of membrane-bound to total Dmoesin signals from replicate experiments similar to that shown in A. Although illumination halves levels of WT Dmoesin in association with membranes (P < 0.01; n = 3), no significant modification of Dmoesin distribution is provoked by illumination of Dmoesin-T559A-GFP and Dmoesin-T559D-GFP. The error bars are SEM.
Mentions: To support this interpretation using a different approach, we analyzed the impact of T559 mutations on Dmoesin movement through biochemical characterization. The membrane and soluble fractions of head extracts from flies expressing Dmoesin-WT-GFP, Dmoesin-T559A-GFP, and Dmoesin-T559D-GFP were fractionated by SDS-PAGE and analyzed by Western blots using anti-GFP antibodies (Fig. 8 A). Although illumination reduced the Dmoesin level in the membrane fraction and concomitantly increased Dmoesin levels in the cytosol of Dmoesin-WT-GFP, the distribution of phosphorylation-defective Dmoesin mutants was unmodified by light (Fig. 8, A and B). As expected, the major fraction of Dmoesin-T559A-GFP was restricted to the soluble fraction, whereas the Dmoesin-T559D-GFP appeared in both the membrane-associated and the cytosol fractions (Fig. 8).

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