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Regulation of phototransduction responsiveness and retinal degeneration by a phospholipase D-generated signaling lipid.

LaLonde MM, Janssens H, Rosenbaum E, Choi SY, Gergen JP, Colley NJ, Stark WS, Frohman MA - J. Cell Biol. (2005)

Bottom Line: Drosophila melanogaster phototransduction proceeds via a phospholipase C (PLC)-triggered cascade of phosphatidylinositol (PI) lipid modifications, many steps of which remain undefined.We describe the involvement of the lipid phosphatidic acid and the enzyme that generates it, phospholipase D (Pld), in this process.Pld() flies exhibit decreased light sensitivity as well as a heightened susceptibility to retinal degeneration.

View Article: PubMed Central - PubMed

Affiliation: Program in Molecular and Cellular Biology, Center for Developmental Genetics, Stony Brook University, Stony Brook, NY 11794, USA.

ABSTRACT
Drosophila melanogaster phototransduction proceeds via a phospholipase C (PLC)-triggered cascade of phosphatidylinositol (PI) lipid modifications, many steps of which remain undefined. We describe the involvement of the lipid phosphatidic acid and the enzyme that generates it, phospholipase D (Pld), in this process. Pld() flies exhibit decreased light sensitivity as well as a heightened susceptibility to retinal degeneration. Pld overexpression rescues flies lacking PLC from light-induced, metarhodopsin-mediated degeneration and restores visual signaling in flies lacking the PI transfer protein, which is a key player in the replenishment of the PI 4,5-bisphosphate (PIP2) substrate used by PLC to transduce light stimuli into neurological signals. Altogether, these findings suggest that Pld facilitates phototransduction by maintaining adequate levels of PIP2 and by protecting the visual system from metarhodopsin-induced, low light degeneration.

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Pld is expressed in the retina and localizes to the photoreceptor cell body. (A–C) Immunostaining of whole-mounted retinas with an affinity-purified, anti-Pld antiserum (A) and with fluorescently labeled phalloidin to visualize the actin-rich rhabdomeres (B). Pld was detected in the photoreceptor cell body and at the base of the rhabdomere (arrows), where a small region of overlap with actin was observed in many cells (C). (D) Retinal tissue sections from Pld mutant flies raised for 6 wk under a 12-h light/12-h dark cycle were prepared and imaged using electron microscopy. Indistinguishable images were obtained from Canton-S flies raised under identical conditions (not depicted). CB, cell body; R, rhabdomere; SRC, subrhabdomeric cisterna.
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fig3: Pld is expressed in the retina and localizes to the photoreceptor cell body. (A–C) Immunostaining of whole-mounted retinas with an affinity-purified, anti-Pld antiserum (A) and with fluorescently labeled phalloidin to visualize the actin-rich rhabdomeres (B). Pld was detected in the photoreceptor cell body and at the base of the rhabdomere (arrows), where a small region of overlap with actin was observed in many cells (C). (D) Retinal tissue sections from Pld mutant flies raised for 6 wk under a 12-h light/12-h dark cycle were prepared and imaged using electron microscopy. Indistinguishable images were obtained from Canton-S flies raised under identical conditions (not depicted). CB, cell body; R, rhabdomere; SRC, subrhabdomeric cisterna.

Mentions: The findings in Fig. 2 suggested that Pld might function by regulating the phototransduction lipid cycle. As one possibility, Pld could act in the SRC to add PA into the phototransduction lipid cycle in order to generate more PI and ultimately replenish the PLC-depleted PIP2. As a second, nonexclusive possibility, Pld might function in the rhabdomere to directly stimulate the PI4P5K-catalyzed phosphorylation of PIP to generate PIP2. Protein localization was examined using an affinity-purified polyclonal rabbit antiserum that was directed against the Pld NH2 terminus. Pld staining was observed in the photoreceptor cell body, in some cases most strongly at the base of the rhabdomere (Fig. 3, A–C), which would be consistent with partial localization to the SRC. Pld was not observed in the remainder of the rhabdomere where light transduction occurs.


Regulation of phototransduction responsiveness and retinal degeneration by a phospholipase D-generated signaling lipid.

LaLonde MM, Janssens H, Rosenbaum E, Choi SY, Gergen JP, Colley NJ, Stark WS, Frohman MA - J. Cell Biol. (2005)

Pld is expressed in the retina and localizes to the photoreceptor cell body. (A–C) Immunostaining of whole-mounted retinas with an affinity-purified, anti-Pld antiserum (A) and with fluorescently labeled phalloidin to visualize the actin-rich rhabdomeres (B). Pld was detected in the photoreceptor cell body and at the base of the rhabdomere (arrows), where a small region of overlap with actin was observed in many cells (C). (D) Retinal tissue sections from Pld mutant flies raised for 6 wk under a 12-h light/12-h dark cycle were prepared and imaged using electron microscopy. Indistinguishable images were obtained from Canton-S flies raised under identical conditions (not depicted). CB, cell body; R, rhabdomere; SRC, subrhabdomeric cisterna.
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Related In: Results  -  Collection

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fig3: Pld is expressed in the retina and localizes to the photoreceptor cell body. (A–C) Immunostaining of whole-mounted retinas with an affinity-purified, anti-Pld antiserum (A) and with fluorescently labeled phalloidin to visualize the actin-rich rhabdomeres (B). Pld was detected in the photoreceptor cell body and at the base of the rhabdomere (arrows), where a small region of overlap with actin was observed in many cells (C). (D) Retinal tissue sections from Pld mutant flies raised for 6 wk under a 12-h light/12-h dark cycle were prepared and imaged using electron microscopy. Indistinguishable images were obtained from Canton-S flies raised under identical conditions (not depicted). CB, cell body; R, rhabdomere; SRC, subrhabdomeric cisterna.
Mentions: The findings in Fig. 2 suggested that Pld might function by regulating the phototransduction lipid cycle. As one possibility, Pld could act in the SRC to add PA into the phototransduction lipid cycle in order to generate more PI and ultimately replenish the PLC-depleted PIP2. As a second, nonexclusive possibility, Pld might function in the rhabdomere to directly stimulate the PI4P5K-catalyzed phosphorylation of PIP to generate PIP2. Protein localization was examined using an affinity-purified polyclonal rabbit antiserum that was directed against the Pld NH2 terminus. Pld staining was observed in the photoreceptor cell body, in some cases most strongly at the base of the rhabdomere (Fig. 3, A–C), which would be consistent with partial localization to the SRC. Pld was not observed in the remainder of the rhabdomere where light transduction occurs.

Bottom Line: Drosophila melanogaster phototransduction proceeds via a phospholipase C (PLC)-triggered cascade of phosphatidylinositol (PI) lipid modifications, many steps of which remain undefined.We describe the involvement of the lipid phosphatidic acid and the enzyme that generates it, phospholipase D (Pld), in this process.Pld() flies exhibit decreased light sensitivity as well as a heightened susceptibility to retinal degeneration.

View Article: PubMed Central - PubMed

Affiliation: Program in Molecular and Cellular Biology, Center for Developmental Genetics, Stony Brook University, Stony Brook, NY 11794, USA.

ABSTRACT
Drosophila melanogaster phototransduction proceeds via a phospholipase C (PLC)-triggered cascade of phosphatidylinositol (PI) lipid modifications, many steps of which remain undefined. We describe the involvement of the lipid phosphatidic acid and the enzyme that generates it, phospholipase D (Pld), in this process. Pld() flies exhibit decreased light sensitivity as well as a heightened susceptibility to retinal degeneration. Pld overexpression rescues flies lacking PLC from light-induced, metarhodopsin-mediated degeneration and restores visual signaling in flies lacking the PI transfer protein, which is a key player in the replenishment of the PI 4,5-bisphosphate (PIP2) substrate used by PLC to transduce light stimuli into neurological signals. Altogether, these findings suggest that Pld facilitates phototransduction by maintaining adequate levels of PIP2 and by protecting the visual system from metarhodopsin-induced, low light degeneration.

Show MeSH
Related in: MedlinePlus